SE418914B - Method for processing of frequency-modulated information on a storage element and apparatus for processing of information in the form of a frequency-modulated signal on an information element - Google Patents

Abstract

The invention concerns the method and apparatus for recording video information in the form of a frequency- modulated signal on a video disk element 10 and for recovery of the video information from the video disk element. The recording apparatus has a laser as a source 30 of a laser writing beam 29, 29' and an optical writing unit 40, 41 for directing the stationary laser writing beam against a moveable video disk element 10. The video disk element comprises a substrate 22, which carries a coating 26 that can be influenced by light on at least one surface 24. The optical writing unit 40, 41 focuses the beam into a tiny spot of light 42 with a diameter of around 1 micrometer on the coating layer 26 which can be influenced by light. The intensity of the focused spot can be altered under control by a light intensity modulating unit 44. This light intensity modulator 44 changes the intensity of the laser writing beam 29, 29' with respect to a predetermined threshold intensity, which is high enough to form a first type of markings 37 in the coated layer. The length of the first type of marking depends on the speed of movement of the video disk element 10 and the time during which the intensity of the writing laser exceeds the predetermined or material-dependent threshold intensity. When the intensity of the laser writing beam drops below the predetermined threshold intensity, the formation of the first type of marking 37 ceases. The intervening portions of the light-influenced coating layer that are situated between consecutive markings of the first type serve as a second type of marking 38. A motion control unit 28 rotates and translates the video disk element relative to the intensity-modulated writing light beam. In this way, a linear sequence of first and second markings is formed on the substrate. The first and the second markings 37, 38 have variable length and represent the frequency- modulated signal used for the recording. <IMAGE>

Description

10 15 20 25 30 35 40 78101284 »2 second part of the frequency modulated signal. The storage element is moved with a constant speed.

The apparatus for writing a frequency modulated signal on a video disc element comprises a moving writing beam and a video disc element mounted on one turntable. The disc is driven by means of a motion control unit, which rotates the disc exactly circular with a constant rotational speed, and a translation drive for moving the writing beam at a very constant and very low speed along a radius of the rotating disk. The rotary drive of the disc is synchronized with the translational drive of the writing beam to produce a helical track with predetermined climb. In a predetermined embodiment, the space between adjacent tracks is in the spiral 2 / ßbm from center to center. The markings are formed with a width av l / ßum. This leaves a gap or a safety area of 1, acm between markings in adjacent tracks. If desired, the markings can be conducted as concentric circles by the translation of the writing beam in cremation steps.

According to a preferred embodiment, a microscope lens is applied to a constant height above the video disc element on an air storage. This lens is used to focus the writing beam on the photosensitive surface of the video disc element.

The constant height is necessary due to the short focal length of the lens.

A dry microscope lens with a numerical aperture of 0.65 is used to focus a laser writing beam to a spot with a diameter of 1, øL4n on the light sensitive coating. Since the coating rotates at a relatively high speed, the length of the marking depends on the duration of the the site exceeds the intensity required to form such a mark.

A linearly polarized argon laser is used as the source of the writing beam.

A Pockel cell is used to rotate the polarization plane of the writing beam with the looking at its fixed plane of linear polarization. A linear polarizer attenuates the rotated writing beam to an extent proportional to the difference in polarization between the light in the writing beam and the axis of the linear polarizer.

The combination of the Pockel cell and the linear polarizer modulates the writing beam with the video information intended for storage. This modulation follows the pattern, provided by control signals for the Pockel cell.

The video signal to be recorded is applied to a frequency modulator. circuit. The output signal from the modulator circuit is a square wave, the frequency of which is portional to the video signal. The duration of each cycle of the square waveform is variable, which is characteristic of a frequency modulated signal. A square wave characterized in that it has an upper voltage level and a lower voltage level.

The upper and lower voltage levels of the square wave are amplified by the Pockel cell drive and is used to control the Pockel cell. The Pockel cell changes polarity the angle of incidence of the light passing therethrough depending on the instantaneous l0 15 20 25 30 35 40 7810128-4 voltage level of the control signal.

In a first operating state, which is operable in dependence on a voltage level of the square control signal applied to the drive unit of the Pockel cell, passes the light beam unhindered through the combination of the Pockel cell and it linear polarizer with an initial intensity, which is large enough for to form a first mark in a coating which can be actuated by light.

When the control signal changes to represent its second voltage level, the The Pockel cell polarizes the writing beam forming the light to a new polarization angle. As a result of this change in polarization of it the writing beam forming the light, there is a breaking adjustment between the polarization the angle of view of the light emanating from the Pockel cell and the preferred one the polarization angle of the linear polarizer. In this case, it works the linear polarizer as a dimmer and less light passes through the linear polarizer. This reduces the light intensity of the writing beam to below it intensity required to form said first mark in that of light affectable coating.

Different types of video disc elements can be used with this writing or recording procedure and this apparatus. Each such video disc element has a special design. According to a first embodiment, the video disc element comprises a glass substrate having an upper surface which carries a thin metal coating as one of light-acting coating. In this embodiment, the writing beam forms openings with variable length in a groove-like manner in the metal coating.

With the first embodiment, a portion of the glass substrate is exposed in each opening. The exposed portion of the glass substrate appears as an area with non-reflective light reflectance to an incident reading beam.

The intermediate portion of the metal coating has a reflective reflection måga, which means that a significant part of the reflected light returns along the path of the incident light beam. Non-reflective reflectivity bears that no significant part of the incident beam is reflected along the trajectory of the incident beam.

In a second embodiment, the video disc element comprises a glass substrate with an upper surface, which carries a thin layer of a photoresist which is susceptible to light coating. With this embodiment, the writing beam forms variable length having areas of exposed and unexposed photoresist material in a track-like manner in the photoresist coating.

A preferred embodiment of a reading apparatus utilizes a reading device. laser for generating a polarized, collimated light beam with a preferred polarization risation angle. An optical reading system directs and images the laser beams to hit the markings supported on the surface of the video disc element. The video disc element is used for storing a frequency modulated signal on its surface in the form of a set 10 l5 20 25 30 35 40 781012844 I 4 linear areas. The areas have varied reflective light reflection and non-reflective light reflectance. The optical reading system focuses the reading beam to a light spot with a diameter of about 1 micrometer and directs the focused spot to fall on the set of linear areas. Reading the intensity of the beam is adjusted so that a sufficiently strong reflected reading beam signal is picked up by the optical reading system.

The motion control unit of the turntable is arranged to rotate the video disc element with a sufficiently uniform rotational speed for reconstruction of the original frequency stored modulated frequency. A thus stored, typically frequency modulated signal varies in frequency between 2 MHz and 10 MHz. The video disc element rotational speed is preferably set to about 1800 rpm to change the spatially modulated frequency modulated signal to an electrical signal in real time. The motion control unit comprises a translation drive unit for moving the reading beam at a very constant and very low speed along the radius of the rotating disk so that the light beam falls on the one present on the disk the set of lines with light-reflecting and light-scattering areas.

The reflected reading captured by the optical reading system the beam is directed to a light sensing circuit for changing the intensity modulus. reflected light beam to a frequency modulated electrical signal, which responds against the intensity modulated reflected light beam.

A polarization selective beam splitting element is located in the reading the path of the beam between the reading laser source and the video disc element. After the reading beam passed through the polarization-selective beam-splitting element the reading light beam is linearly polarized in the preferred plane. A quartz wave longitudinal plate is arranged between the polarization-selective beam-splitting element output and the video disc element. The quartz wavelength plate changes the light in the reading the beam from linear polarization to circular polarization. The reflected light maintains its circular polarization until it passes through the quartz wavelength plate a second time. During this second passage through the quartz wavelength plate changes the reflected light by circular polarization back to linearly polarized light rotated 90 ° from the preferred plane determined by the above-mentioned polarization sation-selective beam splitting element.

The polarization-selective beam-splitting element is susceptible to dependence of this 90 ° rotation in the reflected light beam to deflect it reflected the light beam to the light sensing circuit and prevents the light beam from re-entering the reading laser source. IN A scattering lens is used in the optical reading system for scattering the substantially parallel light beam from the reading laser source to at least fill the lens aperture. 7 In a second embodiment of the optical reading system is an optical 10 15 20 30 35 40 '7810128-4 filter placed in the path of the reflected reading beam to filter out light with all wavelengths except for the wavelengths which the light from the the laser source has.

In a recording or recording apparatus, only the recording or the write function to write the frequency modulated information on one video disc element. In a video disc player, only the read function is used. for to retrieve the frequency modulated information stored on the surface of the video disc element.

In a third operating state, the read and write functions are combined in one even machine. In this combined device, the reading function is used for control of the accuracy of the information entered by the write function.

To realize the monitoring function, a reading beam is added from a helium-neon (He-Ne) reading laser to the path of the writing beam. The reading optics is set to direct the reading beam through the microscope lens during a small angle with respect to the writing beam. the angle is selected so that the reading beam illuminates an area on the same track that is written by the writing beam, but at a point that lies about 4-6 micrometers downstream relative to the writing spot. More specifically, readings are to fall on the information track just formed by the writing beam.

Sufficient time has been allowed to elapse for the formation of the information markings on the video disc element. In this way, the reading beams are thrown at alternating areas with different reflectivity. In the case of an embodiment of the reading tube apparatus, the reading falls the jet of metal which is not heated by the writing jet and falls also on the glass substrate which is exposed in the openings which are just formed by it fl wwande stains. The areas with different reflectivity serve to change one falling reading beam of constant intensity to an intensity modulated, reflected reading beam.

In this monitoring operating mode, the laser reading beam is selected to operate with a wavelength different from the wavelength of the laser writing beam. A wavelength selection optical filter is placed in the path of the reflected light beam and has a tape, which includes the laser reading beam. Possible light of the laser writing beam, which follows the reflected path of the reading beam, is eliminated by the filter and can therefore do not interfere with the reading procedure.

The monitoring operating condition is used in connection with recording or writing the video information on the video disc element as an aid for checking the quality of the recorded signal. The output signals from the reading path are presented on an oscilloscope and / or a television monitor. Visual inspection of this presented signal indicates whether the markings are formed with the preferred operating frequency.

The preferred operating frequency is obtained when averaging the length of a mirror reflecting area, which represents a half cycle of a frequency modulated signal, is the same as the next subsequent area with non-reflective reflectivity, which represents the next subsequent half cycle of a frequency modulated signal.

Operating mode reading after writing or the supervisory operating 10 15 20 25 30 35 40 ? s1o12a-4 0 the condition is also used for error checking, especially on digital type information recorded. The entered video information is delayed for an interval equal to the accumulated values for the time delay, which begins with the frequency modulation of the input video information signal during the recording process and continues during the frequency demodulation of the recovered, reflected signal from the sensing circuit, and includes the delay in moving time of the point on the storage element, when it is moved from the point of storage of the input video the information signal to the point where the reading light beam hits. The recycled the information is then compared with the delayed input information due to role of accuracy. If there are too many differences, there is reason to either repeat the check and reset the unit or discard the disc element.

The reading device is suitable for use in connection with a household television tuner by adding a radio frequency modulator for adding the video signal to a suitable carrier frequency, which is adapted to one of the channels at a conventional household television receiver. The conventional television receiver the receiver then processes this signal in the same way as it is received from a conventional national transmitter station.

The invention is described in more detail below with reference to the accompanying drawing, Fig. 1 is a block diagram of the recording or writing apparatus, Fig. 2 is a cross-sectional view through a portion of a video disc element before being subjected to it recording by using the recording apparatus according to Fig. 1. Fig. 3 is a partial plan view from above of a video disc element after it has been subjected to it recording using the recording apparatus according to Fig. 1, Fig. 4 is a diagram showing the path shape of a video signature used in the recording the apparatus of Fig. 1, Fig. 5 is a diagram showing a waveform of a frequency modulated signal, which is used in the recording apparatus according to Fig. 1, Fig. 6 is "A graphical representation of the intensity of the writing laser used in the recording apparatus according to Fig. 1, Fig. 7 is a graphical representation showing the modulated recording or writing beam and how it changes by means of the drawing apparatus according to Fig. 1, Fig. 8 is a circular cross-sectional view through the the element in Fig. 3, which view is taken along the line 8-8 in Fig. 3, Fig. 9 is a detailed block diagram of a suitable motion control unit, Fig. 10 is a block diagram of a reading apparatus, Fig. 11 is a block diagram of a combined reading device; and recording apparatus, Fig. 12 is a schematic visual representation showing the reading beam and the recording beam passing through a single objective lens, which is used in the block diagram according to Fig. 1 and Fig. 13 is a wiring diagram above a suitable stabilizing circuit intended to be used in the recording apparatus according to Fig. 1.

The same reference numerals have been used to indicate the same elements in the different drawing figures. The terms recording, recording and storage are used 10 15 20 25 30 35 40 7810128-4 interchangeable with the term writing. The term recycling is used interchangeably with the tin reading.

The device for storing video information in the form of a frequency modulated one signal on an information storage element 10 is shown in Fig. 1. One as a source for one information signal serving circuit 12 is used to provide an information signal, which is to be recorded. This information signal, which is transmitted via a line 14, is a frequency modulated signal having its information content in in the form of a carrier frequency with frequency changes over time, which represent it for record intended information. Fig. 5 shows a typical example of a frequency modulated signal. The information signal source circuit 12 utilizes a video signal circuit 16 for providing an information signal on a line 18, which signal has its information content in the form of a voltage, which varies with the time format. Fig. 4 shows a typical example of a voltage signal which varies with time.

A frequency modulator circuit 20 is operable depending on the video signal circuit 16 for conversion of the time-varying signal to the frequency shown in Fig. 5. vein modulated signal on line 14.

The information storage element 10 is supported on a turntable or a turntable. plate 21. The element 10 is shown in Fig. 2 without any markings formed thereon and comprises a substrate 22 with a first surface 24 and one which can be actuated depending on light skkt 26, which covers the first surface 24. A motion control unit 28 is arranged to apply uniform movement of the storage element 10 relative to a writing beam 29 ', which is generated of a light source 30. The motion control unit 28 is shown and described in more detail below with reference to Fig. 9. The motion control unit 28 comprises a rotary drive circuit 32 for apply uniform rotational movement to the information storage element 10 and a translated drive circuit 34, which is synchronized with the rotary drive circuit 32 for moving of the focused light beam 29 'radially over the coating layer 26. the control unit 28 further comprises an electrical synchronization unit 36 for maintenance of a constant ratio between the rotational movement applied to the element 10 by means of the rotary drive circuit 32, and the translational motion applied to the light beam 29 'by means of the translation drive circuit 34.

The light source 30 produces a light beam 29, which has a sufficiently high intensity. to cooperate with or change the coating layer 26 while it is present is in motion and is mounted in position on the movable information storage element 10.

In addition, the intensity of the light beam 29 'is high enough to produce permanent markings or marks in the coating 26, which represent it for recording intended information. A suitable light source 30 includes a writing laser for generation of a collimated writing beam consisting of polarized, monochromatic light.

Fig. 2 shows a cross-sectional view through a first embodiment of a suitable one video disc element 10. A suitable substrate 22 consists of glass and has a smooth, flat, flat first surface 24. The light-sensitive coating layer 26 is formed on the surface 10 15 20 25 30 35 40 7810128-4 24.

In one of the described embodiments, the coating layer 26 is a thin, opaque, metallized layer with suitable physical properties to enable localized heating in dependence on the layer being hit by the writing light beam 29 from the writing laser 30. During operation, the heating causes local melting of the coating. layer 26 followed by retraction or withdrawal of the molten material towards the perimeter of the molten area. In the case of solidification, a permanent opening is left as shown at 37 in Figs. 3 and 8, in the thin metal coating layer 26. the opening 37 is a type of marking, which is used to represent the information. - In this embodiment, successively located openings 37 are separated by means of a portion 38 of the unaffected coating layer 26. The portion 38 is the second type of marking, which is used to represent the information. A more detailed description as to the method by which the markings 37 and 38 represents the fi sequence modulated signal, is given with reference to Figs. 5 - 8.

A moving optical unit 40 and a beam controlling optical unit 41 determine or together determine an optical path of the light beam 29 exiting the light source 30. The optical units project the reading beam 29 to a spot 42 the coating layer 26 supported by the storage element 10. is also centered by the line denoted by the reference numerals 29 and 29 '.

A light intensity modulation unit 44 is located in the optical path 29 between the light source 30 and the coating layer 26. In its widest operating state intensity modulates the light intensity modulating unit the light beam 29 with the call the intended information. The modulation unit 44 operates under the control of a amplified form of the frequency modulated signal shown in Fig. 5. This frequency modulated signal causes the unit 44 to change between its higher light transmission and its lower light emitting state during each cycle for the frequency modulated signal. This rapid change between transmission states modulates the light beam 29 with the frequency modulated signal for storage.

The light beam 29 is modulated as it passes through the light intensity modulation unit 44. Then the modulated light beam, which is now denoted by reference numeral 29 ', on the coating layer 26 of the optical units 40 and 41. When the modulated light beam 29 'falls on the coating layer 26, the marker is formed. rings on the layer 26, which markings represent the frequency intended for storage. modulated the signal.

The light intensity modulation unit 44 comprises an electrically controllable sub- unit 46, which is operable depending on the frequency modulator 20 for varying the intensity of the light beam 29 'over a predetermined intensity at which it focused the beam 29 'changes the coating layer 26, which is supported by the information storage element mentet l0. In addition, the electrically controllable subassembly 26 can be actuated of the frequency modulator 20 for varying the intensity of the light beam during a predetermined l0 l5 20 25 30 35 40 '7810128-4 tuned intensity, at which the focused beam 29 'is not able to change the coating layer 26. The changes brought about in the coating layer 26 represent the frequency modulated signal for storage. When the coating layer 26 consists of a photoresist layer, which is supported on the information storage element 10, the changes are in the form of exposed and non-exposed photoresist sections with a dimension analogous to that previously mentioned with respect to the markings 37 resp. 38.

When the coating layer 26 supported by the information storage element 10 is a metal coating, the electrically controllable subassembly 46 varies with the writing beam 29 'intensity over a first predetermined intensity at which it focused the jet 29 'melts the metal coating without evaporating it, and also varies the intensity of the writing beam below the predetermined intensity at which the The radius 29 'is not capable of melting the surface of the metal.

The light intensity modulation unit 44 comprises a stabilizing circuit 48 for generating a feedback signal, which is used for temperature stabilization of the working level of the electrically controllable subunit 46 for it to operate between a predetermined higher light intensity and a predetermined lower light intensity level. The light intensity modulation unit 44 has a light sensing circuit for sensing of at least a portion, shown at 29 ", of the light beam emitted from it electrically controlled subunit 46 to generate an electrical feedback signal, which represents the average intensity of the beam 29 '. The feedback signal is connected to the electrically controllable subassembly 46 via lines 50a and 50b to stabilize lisera work level.

The light sensing device generates an electrical feedback signal, which is representative of the average or mean of the modulated light beam 29 ' intensity. In this way, the light intensity modulation unit 44 is stabilized to emit the light beam with a substantially constant average power level. Stabilization circuit 48 also has a level setting device for selectively setting it average power level of the light beam 29 'to a predetermined value for achieving coming from a preferred duty cycle in either a coating layer 26 of metal or a photoresist or other material.

The movable optical unit 40 comprises an objective lens 52 and a hydrodynamic lens. air storage 54 for carrying the lens 52 over the full eyelet layer 26. The off The laser beams 29 'generated by the laser source 30 consist of substantially parallel light beams In the absence of the lens 66, these have substantially parallel light rays substantially none tendency to diverge. Thus, the objective lens 52 has an entrance aperture or aperture. turn 66, which has a larger diameter than the diameter of the light beam 29 '. The flat convex the scattering lens 66, which is located in the path of the light beam 29 ', is used to scatter the substantially parallel loop beams 29 'so that it at least fills the objective lens 52 lnträdesöpnnlng 56.

The beam controlling optical unit 41 comprises a number of mirror elements 58, 60, lÛ l5 20 25 30 40 7810128-4 "J 62 and 64 to deflect the light beams 29 'and 29 "as desired. The mirror 60 is shown as a flat mirror and is used to create strictly circular tracks instead for the drawn spiral grooves. When generating spiral grooves, only one fixed is required Mirror.

As previously mentioned, the light source 30 generates a polarized laser beam 29.

The electrically controllable subassembly 46 rotates the polarization of this laser beam 29. plane under the control of the frequency modulated signal. A suitable electrically controllable subassembly comprises a Pockel cell 68, a linear polarizer 70 and a drive unit 72 for the Pockel cell. The drive unit 72 is essentially a linear amplifier and is impact-1 bar depending on the frequency modulated signal on line l4. The output signal from the Pockel cell drive 72 provides drive signals to the Pockel cell 68 for rotation of the polarization plane of the laser beam 29. The linear polarizer 70 is oriented in a predetermined relationship with respect to the original polarization plane of the laser beam 29 emitted from the laser source 30.

As shown in Fig. 7, the axis of the linear polarizer 70 is for maximum luminosity. transmission located at right angles to the polarization angle of the light emitted from source 30. As a result of this arrangement, the minimum amount of light emits from risator 70 when the writing beam 29 is applied by the Pockel cell 28 a rotation of 0 °. Maximum amount of light exits from the polarizer 70 when the writing beam 29 by means of Pocket cell 28 is subjected to a rotation of 900. This described arrangement of the linear polarity risator is only a preferred choice. By aligning the axis of the polarizer 70 for transmission of the maximum amount of light with the polarization angle of that from the laser source 30 emitted light, the maximum and minimum states will be opposite from that described, when the light beam is subjected to a rotation of 0 ° and 900. However, the typewriter will work essentially the same way. The linear the polarizer 70 serves to attenuate the intensity of the beam 29, which is rotated away from its natural polarization angle. It is this damping function by the linear polarizer 70, which forms a modulated laser beam 29 ', which corresponds to the frequency modulated signal. A so-called "Glan prism" is suitable for use as a linear polarizer 70.

The Pockel cell drive 72 is AC connected to the Pockel cell 68.

The stabilizing feedback circuit 48 is DC connected to the Pockel cell 68.

Figs. 4-7 show selective waveforms for electrical and optical signals, which appear in the embodiment shown in Fig. 1 One of it as a video signal video signal generated in the circuit 16 is shown in Fig. 4. A typical device for generating video such a video signal is a television camera or a video recording device which reproduces a previously recorded signal generated by a television vision camera. A light spot scanner is another source for such a video signal. The The information signal shown in Fig. 4 is typically a signal with the voltage 1V peak peak, which signal has its information content in the form of a by means of a line 73 10 15 20 25 30 35 40 7810128-4 represented voltage, which varies with the time format. The maximum instantaneous change the speed of a typical video signal is limited by the bandwidth of 4.5 MHz. This video signal is of that kind, which can be directly presented on a television monitor.

The video signal shown in Fig. 4 is applied to the frequency modulator 20 in Fig. 1.

The modulator 20 generates the frequency modulated waveform 74 of Fig. 5. the content of the road source in Fig. 5 is the same as the information content in the waveform in Fig. 4, but the shape is different. The information signal in Fig. 5 is a frequency modulated signal, which has its information content in the form of a carrier signal, which has frequency variations with respect to the time around a center frequency. By comparison from the signals in Figs. 4 and 5 it can be seen that the lower amplitude range, which is generally denoted by 75, of the video waveform 73 in Fig. 4 corresponds to the lower frequency portion of the frequency modulated signal 74 of Fig. 5. Such a period of the frequency the lower frequency portion of the vein modulated signal 74 is generally indicated by a parenthesis 76.

A higher amplitude range, generally designated by the reference numeral 77 of the video waveform 73, corresponds to the higher frequency portions of the frequency modulus. a complete period of the frequency modulated signal 74 higher frequency portion is indicated by a parenthesis 78. An intermediate amplitude range generally denoted by a reference numeral 79, of the video waveform 73, corresponds to the intermediate frequency portions of the frequency modulated signal 74.

A single period of the higher frequency portion of the frequency modulated signal, which represents the intermediate amplitude range 79, is indicated by a parenthesis 79a.

A comparison of Figs. 4 and 5 shows that the frequency shown in Fig. 1 the modulator 20 converts the time-varying voltage signal in Fig. 4 to a frequency modulated signal shown in Fig. 5.

Fig. 6 illustrates the intensity of the writing generated by the writing laser 30. the intensity of the writing beam 29 is shown to have a constant level, which is represented by line 80. After an initial start-up process, this intensity remains unchanged.

Fig. 7 illustrates the intensity of the writing beam 29 'after its passage through the light intensity modulation unit 44. The intensity modulated writing beam is displayed with a plurality of upper peaks 92, which represent the light intensity modulation unit 44 higher light transmission conditions, and with a plurality of valleys 94, which represent the lower light transmission state of the light intensity modulation unit 44. Line 80, representing the maximum intensity of the laser 30 is superimposed on the waveform 29 'for to show that any loss of light intensity is obtained in the unit 44. This loss is indicated by means of a line 96, which shows the difference in the intensity of that generated by the laser 30 the intensity of the light beam 29 'and the maximum intensity 92 of that of the unit 44 modulated light beam 29 '.

This intensity modulation of the write beam 29 to form an intensity ~ modulated writing beam? 9 'is best neutralized in Figs. 6 and 7. Fig. 6 shows l0 15 20 25 30 35 40 7810128-4 the unmodulated beam 29 with a constant intensity, which is represented by the line 80. Fig. 7 shows the modulated beam 29 'with maximum intensity levels indicated at 92 and minimum intensity levels indicated at 94.

The intensity modulation of the writing beam 29 is related to the 68 of the Pockel cell rotational power, as shown by lines 98, 100 and 102. The intersection of the lines 98 and line 29 'shows the intensity of that emitted from the linear polarizer 70 beam 29 ', when the Pockel cell 68 does not add any rotation to the polarization angle for the light which passes through it. The intersection of line l00 and line 29 ' indicates the intensity of the beam 29 'emitted from the linear polarizer 70, when the Pockel cell 68 adds a rotational N 450 to the polarization angle thereof; light, which passes therethrough. The section between line 102 and line 29 'shows the the beam 29 'emanating from the linear polarizer 70, when the Pockel cell 68 adds a rotation of 900 to the polarization angle of the light which passes thereby.

The formation of an opening, e.g. the opening 37 shown in Figs. 3 and 8, by means of the intensity modulated beam 29 'shown in Fig. 7 is best understood by a comparative see between the two figures 7 ooh 8.

Line 100 is drawn midway between intensity level 92, which represents a higher light transmission state, and intensity level 94, which represents the unit's lower light transmission state. The line 100 represents the intensity, generated by the unit 44, when the Pockel cell 68 rotates the polarization angle thereof writing beam 29, which passes therethrough, over an angle of 450, additionally represents line 100 the threshold intensity of the modulated beam 29 'required to form a mark in the light-sensitive coating layer 26. This threshold is reached by rotating the polarization angle of the write beam 29 through an angle of 45 °.

A comparison between Figs. 7 and 8 shows that an opening 37 is formed below that the Pockel cell 68 rotates the polarization angle of the writing beam 29, which passes nnn thereby, honan vinkoin 4s ° ooh 9o ° ooh: within about 4s °. any opening hiiaao while the Pockel cell rotates the polarization of the passing beam 29 passing through it. : ionsvinhoi nonon vinkoin 4s ° ooh o ° ooh tiiihoko om 4s °.

To return to Fig. 3, there is shown a top view of the video disc element, as shown in Fig. 8 in radial cross-sectional view. An examination of this figure 3 facilitates the understanding of the way in which the set of lines of light-reflecting and light scattering areas 38 and 37 are formed on the video disc element 10. The disc element l0 rotated at a predetermined rotational speed of 1800 rpm and the markings 37 and 38 is formed in the light-actuating coating layer 26 as shown by reference to Fig. 8. The motion control unit 28, which is shown in Fig. 1, forms the openings 37 circular groove-like manner. Reference numeral 104 denotes a section of a inner groove and the reference numeral 105 denotes a section of an outer groove.

A dashed line 106 represents the center line of the track 10 and a dashed line 107 represents the center line of track 104. The length of a line l08 represents the distance 10 15 20 25 30 40 'B 7810128-4 between the center lines 106 and 107 of adjacent grooves 105 and 104. 2 micrometers are a typical distance between the center lines of adjacent tracks. The width of an opening 37 is indicated by the length of a line 109. A typical width of an aperture is 1 micron. meter. The distance between adjacent openings is represented by the length of a line 110. This distance between adjacent tracks is called the intertrack area. region) and typically has an extent of 1 micrometer. The length of an opening is represented by a line 112 and typically varies between 1.0 and 1.5 micrometers.

All of these dimensions depend on many variables in the recorder.

For example, these dimensions vary depending on the frequency interval being generated of the frequency modulator 20, the size of the spot 42 formed by the optical scripts units 41 and 42 and the rotational speed selected for the disc element 10.

Fig. 9 shows a more detailed block diagram of the motion control unit 28 according to Fig. 1. The rotary drive circuit 32 comprises a spindle servo circuit 130 and a spinde1axe1 132. Spinde1axe1n 132 is in one piece connected to the turntable e11er disk spindle 21.Spind1axe1n 132 is driven by means of a motor 134 of the type printed circuit.

The rotary tube provided by the motor 134 is controlled by the spindle servo circuit. 130, which phases the rotational speed of the disc plate 21 at a signal which is generated of a color subcarrier crysta1 osci11a 136 tor), which forms part of the synchronization unit 36. The synchronization unit 36 further has a first division circuit 138 and a second division circuit 140. The first division circuit 138 reduces the color carrier frequency generated in oscillator circuit 136. down to a rotational reference frequency. The spindle axis 132 contains a tacho- meter 143 for generating a frequency signal1 indicating the axis 132 and the disk 21 exact rotational speed. The tachometer signal is obtained via a line 142 and the rotation reference signal from the first division circuit 138 is obtained on a lead 144. The tachometer signal on line 142 is applied to the spin servo circuit 130 and rotated. The reference signal on line 144 is also applied to the spin servo circuit 130.

Circuit 130 compares the phases of these two signatories. When the phase 1 phase of the tachometer signal1 lies before the phase of the rotation reference signal1, the rotation speed is too high and a signal1 is arranged in the spinneret circuit 130 to be fed via a line 146 to the motor 134 in and to reduce the rotational speed and bring the tachometer signal into phase with the rotation reference signal1. When the phase of the tachometer signal1 comes after the rotation reference phase of the purge signal when compared in the spin servo circuit 130, the rotational speed is and a signal is generated in the spindle servo circuit 130 to 148 is applied to the motor 134 in order to increase the rotational speed and bring the tachometer the signal in phase with the rotation reference signal.

The second division circuit 140 reduces the color generated by the oscillator 136 the subcarrier frequency decreases to a transition reference frequency for displacement of transmission driver circuit 34 at a fixed distance for each completed revolution of the electric circuit. element 10. In the preferred embodiment, for each rotational revolution of the element 10 15 20 25 30 35 40 731Û128'4 * 14 The travel distance by means of the translation drive circuit a distance of 2 micrometers.

The crystal oscillator 136 with its two division circuits 138 and 140 operates as an electrical synchronizing circuit for maintaining a constant relationship between the rotational movement of the disc element, which is obtained by means of the rotary drive unit 32, and the translational movement between the writing jet 29 and the coating layer 26 is obtained by means of the translation drive 34.

The movable optical units illustrated in Figs. 1, 10 and 11 are mounted on a support plate, which is shown at 142. This movable plate is driven in the radial direction by means of the translation drive 34, which moves the plate 142 2.0 micrometers per second rotational rotation of the spindle shaft 132. This translational movement is radial with respect to on the rotating disk member 10. The radial displacement at the spindle shaft 132 each rotation revolution is referred to as the ascent or division record. Since the uniformity in the division of the final record depends on smooth movement of the optical units mounted on the plate 142, a lead screw 143 is carefully arranged in the translation drive unit 34, when a translation drive nut 144, which forms engages the lead screw 143 and makes the coupling between the nut 144 and the plate 142 as rigid as possible, which is illustrated by means of a rod 146. In Fig. 10 a reader, which is used to recover the frequency modulated signal, which is stored on the information storage element 10 as a previously described set lines of markings 37 and 38 or a linear sequence of markings 37 and 38.

A reading beam 150 is generated by a reading laser 152, which produces a polarized one. collimated light beam 150. A support member, such as the turntable or turntable 21, used to support the information storage element 10 in a substantially predetermined tuned position.

A stationary optical reading unit 154 and a moving optical unit 156 provides an optical reading path over which the reading light beam 150 is cast between the laser source lb? and the information storage element 10. In addition, either of the optical units are used to focus the light beam 150 on the alternating ones located light-reflecting areas 38 and light-scattering areas 37, which are supported in successive positions on the information storage element 10. The variable the optical unit 156 is used to collect the reflections from the light reflectors areas 38 and the light scattering areas 37. The motion control unit 28 is provided. maintains relative movement between the reading beam 150 and the successive alternately located areas 38 and 37 for reflection of light resp. scattering of light.

The optical units 154 and 156 also determine the optical path, above which the beam reflected from the coating layer is cast. It reflected the path of the beam is denoted by the reference numeral 150 '. This reflected light beam path 150 'includes a portion of the path of the original reading beam 150.

At the parts where the reflected beam 150 'coincides with the reading beam 150, both reference numerals 150 and 150 'are used. A light sensing element 158 is located in the path 150 'of the reflected light beam and is used to generate one 10 15 20 25 30 35 40 * 5 7810128-4 frequency modulated electric signal1, which corresponds to the corresponding failing ref1ek ~ tion. The frequency-modulated electrical signal generated by the light sensing element 158, appears on a line 160 and has its information content 11 in shape of a carrier frequency with frequency changes in time corresponding to the 1st degree information tion. The signal from the light sensing circuit 158 is applied to a discriminator. circuit 162 via an amplifier 164. The discriminator circuit 162 is susceptible to bending of the output1 from the light sensing circuit 158 and is used to change the frequency modulated electrical signal to a time-dependent voltage signal1, which represents the 1st degree information. The time-dependent voltage signal is determined is also drawn as a video signal1 and appears on a line 165. This time dependency voltage signal1 has its information content11 in the form of a voltage which varies with the time format and is suitable for presentation via a Convention11 television monitor 166 and / or an oscilloscope 168.

The optical reading units 154 and 156 further have a polarization selective radiation splitting element 170, which acts as a radiation polarizing element. opposite the reading beam 150 and which acts as a selective beam splitter opposite the reflected beam 150 '. The optical reading units include further a quartz wavelength plate 172. The beam polarizer 170 filters from the reading the beam 150 removes any light paths which are not aligned with the beam of the polarizer. 170 poirisation axis. With the polarization axis of the reading beam 150 fixed with a particular orientation along the element 170 changes the quartz wavelength plate 172 polarization path from 1injär to circular polarization. Element 170 and quartz the wavelength plate 172 are located in the path 150 of the reading light beam. The element 170 is located between the core 152 of the reading beam 150 and the quartz wave longitudinal plate 172.

The quartz path length plate 172 is also located in the reflected reading beam. lane 150 '. The quarter-wavelength plate 172 thus changes not only the reading beam polarization from linear to circular under its path from the reading laser 152 to the information storage element 10, without the quarter-wavelength plate 172 changing also the circularly polarized, reflected light back to the linearly polarized Light, which is rotated 900 with respect to the preferred direction, which is fixed means the core 152 and the element 170. This rotating beam 150 'is selectively directed on the light sensing element 158, which changes the reflected light beam 150 ' to a corresponding electrical signal1. It should be noted that the element 170 is reduced. determines the intensity of the reading beam 150 as it passes therethrough. This reduction the intensity is compensated by the original reading intensity the beam 150 is set to a sufficiently high level to balance this reaction. tion.

The quarter-wavelength plate 172 gives a total rotation of 900 on the reflected one the beam 150 'with respect to the reading beam 150 during the change from the linear pole risation ti11 circular polarization and ti11back to11inar polarization. As 10 15 20 25 30 35 40 7810128-4 " previously mentioned, the element 170 is also a beam splitting cube in the reflected one 'reading beam path l50'. Since the reflected beam 150 ' polarization plane is shifted 900 due to the double passage of the beam through quarter-wavelength plate 172, directs the beam-splitting cube section of the element 170 the reflected reading beam l50 "against the light sensing circuit 158.

A suitable element with the property of a light sensing element 158 is a photo- diode. Each such element 158 is capable of changing the reflected frequency modulated the light beam 150 'into an electrical signal with its information content in the form of a carrier frequency with frequency variations in time, which vary from carrier the frequency. The optical units 154 and 156 further comprise the objective lens 52, which is supported by a hydrodynamic air storage element 54, which supports lens 52 above the coating supported by the information storage element 10 layer 26. As previously mentioned, the reading beam 150 consists essentially of parallel light rays. The objective lens 52 has an entry aperture 56, which has larger diameter than the diameter of the reading beam 150, when generated by the laser beam. source 152. A plano convex scattering lens 154 is disposed between the laser source 152. and the entrance opening 56 of the objective lens 52 for spreading the substantially parallel ones the light beams forming the reading beam 150 to a light beam 150 with a sufficiently large diameter to at least fill the objective lens 52 entrance opening 56. The optical units 154 and 156 further have a number stationary, planar mirrors 176 and 178 to deflect the reading light beam 150 and the reflected light beam 150 'along a path for which it is intended that the reading light beam 150 should fall on the previously mentioned elements.

An optional optical filter 180 is located in the reflected beam path 150 'and filters out all wavelengths with the exception of reading light beam wavelengths¿ The use of this filter 180 improves the image quality of the image presented by the television monitor 166. This filter 180 is significantly, when the reading system is utilized with the writing system, which is approached below with reference to Fig. 11. In a device set up for both reading and writing, a portion of the writing beam 29 is thrown along the reflected reading beam. lens track 150 ”. The filter stops this part of the writing beam and transmits the beams 150 'full intensity.

An optional collection lens 182 is located in the path of the reflected beam 150 'to cast the reflected beam on the light sensing element 158 active area. This collection lens 182 reduces the reflected beam 150 '. 1 diameter and concentrates the light intensity of the reflected beam on the the active area of the sensing element 158.

Amplifier 164 amplifies the output signal from the light sensing element 158 and increases the amplitude of the frequency modulated electrical signal which is generated of the light sensing element 158, for adaptation to input signal requirements of 10 l5 20 25 30 35 40 17 73101284: demodulator l62.

The electric and optical waveforms shown in Figs. 4-7 are also generated the reading apparatus shown in Fig. 10 during recovery of the frequency modulated one the signal, which is stored on the coating layer supported by the disc element 10 Fig. 6 shows a writing laser beam generated by a laser source, which has const intensity, which is represented by line 80. The reading laser 152 generates a reading beam l5O with constant intensity but at a lower level. Fig. 7 shows a intensity modulated laser writing beam. The reflected reading beam l50 'is intense site modulated due to the fact that it hit the light reflectors and light scattering areas 38 and 37, which are supported on the disc member 10. The reflective The read beam 150 'will not be a perfect square wave of the kind which shown in Fig. 7. Instead, the corners of the signal pulses are rounded due to the reading the final dimension of the stain.

Fig. 5 shows a frequency modulated electrical signal with its information content in the form of a carrier signal, which has frequency changes over time varying around the center frequency. The output of the light sensing element 158 is the same type of signal. Fig. 4 shows a video signal with its information content in the form of a voltage, which varies with the time format. The output of the demodulator l62 is the same type of signal.

The motion control unit 28 shown in Fig. 10 operates in the same manner as the motion control unit 28 in Fig. 1. In the reading apparatus, the motion control unit 28 generates a rotary movement of the disc element under the control of a rotary drive unit 32. The unit 28 further generates a translational movement for moving the moving optical image. the reading unit 156 radially over the surface of the storage element.

The unit 28 further has a synchronizing circuit for maintaining one constant relationship between the rotational movement and the translational movement, so that the reading beam l50 hits the information tracks supported by the disc element l0. Sections of typical information traces are shown at l04 and l05 in Fig. 3. _ Fig. 11 shows a block diagram of the combination of the typewriter according to Fig. 1 and the reading apparatus according to Fig. 10. The elements shown in Fig. 11 work on in the same way as previously described, so this detailed function is not repeated here. Only a brief description is given in order to avoid repetition and ambiguity.

The path of the unmodulated writing beam is shown at 29 and the modulated writing beam the path of the beam is displayed at 29 '. A first optical device determines the modulated beam path 29 'between the output of the linear polarizer 70 and the coating layer The stationary optical writing unit 41 includes the mirror 58. The movable, the optical writing unit 40 includes the scattering lens 66, a partially transmitted mirror 200, a flat mirror 60 and the objective lens 52. The modulated writing the beam 29 'is thrown as a writing spot 42 on it depending on the light impenetrable the coating layer and cooperates with the coating to form those previously described the markings. 10 15 20 25 30 35 40 18 781012841 The path of the reading beam is displayed at 150. The optical reading units defines a second optical path for the reading beam 150 between the reading laser 152 and the information storage unit 10. The stationary optical reading unit 1 154 includes the mirror 176. The movable optical reading unit 156 includes the scattering lens 174, the polarization displacement device 172, a second fixed mirror 202, the selective transmitting mirror 200, the flat mirror 60 and Insert 52. The reading beam 150 is thrown as a reading spot 157 at a point located at a downstream distance from the writing area 42, which is more completely is written with reference to Fig. 12. The mirror 200 is a dichroic mirror, which is transmitting at the wavelength of the writing beam 29 'and which is reflective at the wavelength of the reading beam 150 '.

The intensity of the write beam 29 'is greater than the intensity of the reading beam 150.

While the writing beam 29 'must change the light-sensitive coating coating layer 26 to provide markings representing that for storage viewed video signal, the intensity of the reading beam 150 need only be high enough to illuminate the markings formed in the coating layer 26 and provide a reflected light beam 150 'of sufficiently high intensity to produce a good signal after collection by means of the optical reading unit and conversion from an intensity modulated, reflected beam 150 'to a frequency modulated, electric signal medeist the light sensing circuit 158.

The fixed mirror 58 in the optical path of the writing beam and the two fixed mirrors 176 and 202 in the optical path of the read beam are used to direct the write beam 29 'toward the objective lens 56 at a controlled angle in relation to the reading beam 150.

This angle between the two beams incident on the storage element gives a mean space between the writing stains 42 and the reading stains 157, when these are each discarded on the coating layer 26.

A sufficiently large gap in the operation of the apparatus has been found to be 4-6 micrometers. This distance corresponds to an angle1, which is a11tfor 1iten to indicate This is shown in Fig. 12. For the sake of clarity, this angle is exaggerated in Fig. 12.

The reading beam 150 'is demodulated in a discriminator circuit 162 and present. on a conventional television monitor 166 and an oscilloscope 168. The television the monitor 166 displays the image quality of the recording and the oscilloscope 168 displays the video signal. 1en more in deta1j. This read function immediately after the write function makes it possible to momentarily monitor the quality of the video signal1 during the recording operation 1itet. In the event that the quality of the 1graded signal is poor, it is obtained immediately knowledge of this and the writing process can be corrected or also the information Storage element 10, which stores the video information signal of poor quality, race.

During the reading condition reading after recording, the typewriter 30 and 10 15 20 25 30 35 40 7810128-4 the reading laser 152 at the same time. A dichroic mirror 200 is used to combine the reading beam 150 with the writing beam 29 '. At this working condition reading after recording, the wavelength of the writing beam 29 is selected to differ from that of the reading beam 150 wavelength. An optical filter 180 is used to block any part of the writing beam, which followed the path of the reflected reading beam. Consequently the optical filter 180 transmits the reflected reading beam 150 'and the filter removes any part of the laser writing beam 29 'which follows the reflected path l50 '.

In the comparative working state, the function of reading after writing is performed. as described with reference to Fig. 11. When operating under this supervision operating state, a comparator circuit 204 compares the output of the demodulator 162 with it original video information signal obtained from source 18.

More specifically, the video output signal from the discriminator 162 is applied to a comparator 204 over a line 206. The second input signal to comparator 204 is taken from the video source 16 via line 18, a further line 208 and via a delay The delay line 210 applies to the input video information signal a time delay equal to the accumulated delay values starting from the frequency modulation of the input video information signal and on to the frequency demodulation of the recovered electrical signal from the sensing circuit 158. This delay also includes the delay in terms of travel time from the point on the storage element 10 at which the input video information the signal is stored on the information storage element by means of the write spot 42 with continued setting to the point at which the reading spot 157 hits.

The correct delay amount is best achieved by the delay circuit 210 is performed for variable delay, the delay being set to optimal feature.

Under ideal conditions, the video output signal from discriminator 162 is identical in all respects with the video input on lines 18 and 208. Each performance difference represents errors, which may have been caused by defects or defects in the disc the surface of the element or malfunctions of writing circuits. This application is although it is essential when recording digital information, less critical when other information is recorded.

The output of the comparator circuit 204 can be counted in a counter (not shown) for determining the actual number of errors that occur on a disc element.

When the number of errors counted exceeds a predetermined number, the write operation ends tion. If required, a new record can be made on a new disc element. Each disc elements with too many defects can be treated to eat used. In Fig. 11 comparator 204 compares the outputs available on lines 208 and 206. One alternative and more direct connection of the comparator 204 is to compare the output signals from the frequency modulator 20 and the amplifier 164 shown in Fig. 10. l0 l5 20 25 30 35 40 20 '78i0i28-4 Fig. 12 shows in slightly enlarged form the slightly different optical paths for the intensity modulated writing beam 29 'from the writing laser 30 and the unmodulated one the reading beam 150 from the reading laser 152. The information storage element lD is moved in the direction indicated by an arrow Zl7. The figure shows an unexposed portion 26 ' of the coating layer 26 approaching the writing jet 29 'and a linear sequence of openings 37, which leave the intersecting area between the writing jet 29 'and the coating layer 26. The writing beam 29 'coincides with the optical of the microscope objective lens 52 shoulder. The central axis of the reading beam 150, which is denoted by 212, forms an angle with the center axis of the writing beam 29 ', which is designated 214. The angle is damaged by means of a bidirectional arrow 216. small consequence of this small difference in the writing radius' 29 'and the optical paths of the reading beam 150 through the lens 52, the writing spot falls 42 a distance in front of the reading spot l57. The writing spot 42 is in front of the the distance spot l57 a distance equal to the length of a line 218. The length of the line 218 is equal to the angle times the focal length of the objective lens 52. The resulting delay the writing between the writing and the reading allows the molten metal coating layer ' 26 to solidify so that the record is read in its final solidified state.

If it was read too early while the metal was still molten, it would reflect from the edges of the aperture can not produce a high quality signal presentation on monitor l66.

Fig. 13 shows a preferred circuit diagram of a stabilization circuit 48 for a Pockel cell, which circuit is suitable for use in the apparatus of Fig. 1. It is known that a Pockel cell 68 rotates the plane of polarization of a guided writing light beam 29 as a function of an applied voltage, which is illustrated with reference to Fig. 7.

Depending on the individual Pockel cell 68 causes a voltage change of the order of 100 V that the cell rotates the plane of polarization thereof thereby passing light 900. The Pockel cell drive serves to amplify the output signal from the information signal source l2 to an output signal with a peak-to-peak value of l00 V.

This output signal is a properly input drive signal to the Pockel cell 68. the drive unit 72 of the cell generates a waveform which has the shape shown in Fig. 5 and has a voltage value from peak to peak of lD0 V.

The Pockel cell should work at an average rotation of 450 in order to bring the intensity of the modulated light beam to reproduce as faithfully as possible the electric drive signal. A bias voltage must be applied to the Pockel cell to keep the Pockel cell at this average operating point. In practice, it varies the electrical bias voltage, which corresponds to a working point with a rotation of 45 °, tinuerligt. This continuously changing bias voltage is generated by utilization of a servo feedback loop. This servo feedback loop includes the comparison of the average value of the transmitted light with an adjustable reference value and supply of the difference signal to the Pockel cell by means of a direct voltage l0 l5 20 25 30 35 40 Zl 7810128-4 amplifier. This arrangement stabilizes the working point. The reference value can be set to correspond to the average transmission, which corresponds to the the point of rotation above 450 and the servo feedback loop provides correction biases to maintain the Pockel cell at this average rotation of 450.

The stabilizing circuit 48 comprises a light sensing means 225. A silicon photodiode acts as a suitable light-sensing organ. Diode 225 senses one part 29 "of the writing beam 29 ', which is emitted from the optical modulator 44 and passes through the partially reflecting mirror 58, which is shown in Fig. 1. The photodiode_ 225 operates in essentially the same way as a solar cell and is an electrical energy source, when illuminated by incident radiation. An output terminal of the photodiode 225 is connected by a line 227 to a common reference potential 226. Photo- the second output connection of the diode 225 is connected via a line 230 to an input at a differential amplifier 228. The output terminals of the silicon cell 225 are shunted by means of a load resistor 232, which enables a state of linear response.

The second input of the differential amplifier 228 is connected via a line 238 to one adjustable arm 234 of a potentiometer 236. One end of the potentiometer 236 is connected to the reference potential 226 via a line 240. An electrical power source 242 is connected to the other end of the potentiometer 236, which enables input position of the differential amplifier 228 to generate a feedback signal on lines 244 and 246 for setting the average power level for it modulated the laser beam 29 'to a predetermined value.

The output poles of the differential amplifier 228 are resp. connected via resistive elements 248 and 250 and the output lines 244 and 246 to that of FIG showed the 68 input poles of the Pockel cell. The Pockel cell drive unit 72 is AC connected to the Pockel cell 68 by means of capacitive elements 252 and 254, while different The ration amplifier 228 is connected to the Pockel cell 68.

During operation, the system is activated. The part 29 'of the light from the writing beam 29 ', which falls on the silicon diode 225, generates a differential voltage at an input to differential amplifier 228. Initially, potentiometer 236 is set to the average transmission through the Pockel cell corresponds to a rotation of 450.

Then comes, if the average intensity level of the light, which falls on the silicon cell 225 either increases or decreases. a corrective voltage to be generated of the differential amplifier 228. The corrective voltage applied to the Pockel cell 68 has a polarity and a size adapted to return the average intensity level to the predetermined level, selected by setting the input the voltage to the second input of the differential amplifier across line 238 by motion see of the movable arm 234 along the potentiometer 236.

The adjustable arm 234 of the potentiometer 236 constitutes the means for selecting the average intensity level of the light generated by the writing laser 30. Optimal results 10 15 20 25 30 35 40 22 7810128_-¿i is achieved when the length of one opening 37 is exactly equal to the length of the next on the following space 38, as previously described. The setting of the potentiometer 36 is the measure for achieving this similarity in length. When the length of an opening is equal to the length of the next adjacent space, a duty cycle of is obtained type half-half. Such a work cycle can be detected by checking the presence the information just written on the TV monitor and / or the oscilloscope l66 resp. l68, which have been previously described. Commercially acceptable results lies, when the length of an opening 37 varies between 40 and 60% of the total the length of an opening and its next subsequent space. In other words, measured. the length of one opening and the next subsequent_space. the opening can thus have one length, which falls in the range of 40-60% of the total length.

In Fig. 8, a circular cross-section of one is illustrated with reference to Fig. 3 shows an information track, in which a reflective light-reflecting area 38 is located between a pair of non-reflective light-reflecting areas 37. In the circulating learning the cross-sectional view according to Fig. 8, the incident reading or writing beam is moved relative to the element 10 in the direction represented by the arrow 277. This means carries that a reading beam first falls on the reflective light reflecting area 38a and then falls on the non-reflective light reflecting area 37a. In this edition the positive half period of the record is represented the signal of a reflective light reflecting region 38a and the negative half period of the signal to be recorded is represented by the non-reflective light reflective area 37a. The operating cycle of the one shown with reference to Fig. 8 the signal is a 50% duty cycle insofar as the length of the reflecting light the reflecting area 38a, which is represented by a parenthesis 260, is equal to the length of the non-reflective light reflecting area 37a, which later length represented by parentheses 262. This preferred work cycle is accomplished by combined setting of the absolute intensity of the writing beam 29 by setting the power supply of the writing laser 30 and by setting the potentiometer 236 in to a level at which an aperture is formed at the beginning of a 450-g rotation of the polarization angle of the writing beam 29.

To refer to it illustrated with reference to Figs. 7 and 8 the process for forming openings, melting of a thin metal coating layer 26, when the power in the light spot exceeds a threshold value which is characteristic of the nature and thickness of the metal film and the properties of the substrate. Light- the power of the spot is modulated by means of the light intensity modulating unit 44. -from-the-transitions are kept short to make the position of the ends of the holes or openings exactly independent of variations in the melting threshold. Such variations in melting the threshold value may be due to variations in the thickness of the metal the coating layer and / or the use of various materials as information storage layer. 10 15 20 25 30 35 40 781012841 The average light effect required to form one opening in a thin metal coating layer 26 with a thickness between 200 and 300 Å, is of the order of 200 mN. Because the frequency modulated carrier frequency is approximately 8 MHz, 8 x 106 holes are formed with apertures of variable length per second and the energy per hâ1 is 2.5 x 109 jouie.

In this first embodiment, a video disc element 10 is a portion of the gaseous substrate is exposed in each opening. The exposed portion of the gas substrate is acts as an area of non-reflective light reflectivity relative to an infallible de 1ässtrå1e. The portion of the metal coating layer which remains between them The following apertures appear as an area of high light reflectivity an infa11ande 1ässtrå1e.

When the formation of first and second markings takes place using a coating of a photoresist, the intensity of the writing beam 29 'is set to such level, that a 450-degree rotation of the polarization plane produces a light beam 29 'with Threshold intensity for exposure and / or growth effect with photoresist coating layer 26, while the photoresist coating layer is in motion and applied to it movable information storage element 10. The combination of the Pocke1 cell 68 and The G1an prism 70 includes a light intensity modulating element which operates from the 450-degree setting state to a minor light transmitting state stand, which relates to an operating state close to the rotation 00, and to one more light transmitting state, which refers to an operating state close rotation 900. When the intensity of the write beam 29 'increases over the initial input the steady level e11er the predetermined starting intensity, and increases towards it more In the light transmitting state, the incident writing light beam 29 'exposes it to hence the photoresist. This exposure continues after writing intensity when the maximum light transmitting state changes and changes backwards down to the initial predetermined intensity, which relates to the rotation 450 of the polarization plane for the light emitted from the printer 30. When the rotation falls below the value 450, the intensity of the writing beam 29 ', which exits, decreases from the G1as prism 70 below the threshold intensity at which the focused writing the straw is not able to expose the photoresist thereof. This shortcoming The ability to expose the heat photoresist continues after the writing beam intensity reaches the minimum light-transmitting state and begins to rise again against the initial, predetermined intensity, which relates to a rotation of 45 ° of the polarization plane of the light emitted from the writing laser 30.

The drive circuit 72 of the Pocke1 cell is typically a high gain amplifier and high output voltage, which amplifier has an output1 which gives a swing e11er a variation from peak to peak of 100 V of the output voltage. This signal is intended to conform to the requirements required for driving the Pockey cell 68.

Typically, this means that the center voltage value of the output signal from the Pockey cell drive unit 72 provides a sufficient control voltage for driving the Pocke cell 10 l5 20 25 30 35 40 24 '7810128-4 68 over 450, so that about half of the total available light from the laser 30 output from the linear polarizer 70. When the output signal from the drive circuit 72 becomes positive. more light is transmitted from the laser. When the output of the drive 72 becomes negative less light is transmitted from the laser.

In the first embodiment, in which a metal coating layer 26 is used, the output of the laser 30 is set to generate an intensity, which begins to melt the metal layer coating 26 on the disc element 10, when the output signal from the drive 72 is zero and the operating point of the Pockel cell is 450. When the the output 72 of the unit 72 becomes positive, consequently the melting continues. When driven the output 72 of the unit becomes negative, however, the melting stops.

In a second embodiment, in which the photoresist coating layer 26 is used, the output signal from the laser 30 is set to generate an intensity which both illuminates and exposes the photoresist coating 26 as the output of the drive 72 generates its average voltage value. When the output of the drive 72 becomes positive, the actually the illumination and exposure of the photoresist by means of the writing beam to continue take. When the output of the drive "72 becomes negative, the illumination of the photoresist last, but the energy in the writing beam is insufficient to expose the illuminated area. the. The term "expose" is used herein with its technical meaning, indicating the physical calic phenomena, which are based on illumination of a photoresist material. The exposed the photoresist can be developed and the developed photoresist material is removed on conventionally. Photoresist material illuminated by light, which has insufficient intensity to expose the photoresist, can not be developed and removed.

In both the first and second embodiments, as described above, are set the absolute power level 80, which is illustrated by the line 80 in Fig. 6, upwards and downward to achieve this effect by setting the power of the writing laser 30 supply. In combination with this setting of the absolute power level of the print laser 30 also uses, as previously mentioned, the potentiometer 26 to cause markings formed in the coating layer when the beam 29 is rotated an angle greater than 450 °.

In a read-only apparatus of the type shown in Fig. 10 the optical filter 180 is optional and is generally not required. Its use in an apparatus which is used only for reading, causes a slight attenuation of it reflecting light beam, so that a small increase in the intensity of the reading laser 152 is required. to ensure the same intensity at detector l58 compared to a reader, which does not use any filter l80.

The collection lens l82 is optional. In a properly arranged reading machine has the reflecting reading beam 150 'is substantially the same diameter as the photodetector 158 work area. If this is not the case, a collection lens 182 is used to concentrate the reflected reading beam 150 'on the smaller working range of the selected photodetector 158. Although the above, presently preferred embodiments have been described in detail, it will be appreciated that the invention is limited only by the scope of the claims.

Claims (23)

10 15 20 25 30 35 40 PATENšlšRAV A method for processing frequency modulated information on a storage element (10) using a laser light beam (29, 29 '), the frequency modulated information having a carrier signal with frequency changes with time corresponding to the information, the information storage element (10) being arranged to is moved at a constant speed relative to the laser beam (29, 29 ') while the beam is focused on a first surface (26) of the information storage element (10), characterized in that the method includes recording the information on the information storage element (10) during using the laser light beam, and comprising the method steps of generating a frequency modulated electric signal for recording, the intensity of the laser light beam (29 ') transmitted to a light sensitive surface (26) of the information storage element (10) being a control sign1, that reg1erin involves utilizing the transmitted light beam (29 ') to irreversibly change the light-sensitive surface (26) of the information storage element under the control of a portion of the frequency-modulated signal, when the storage element (10) is moved at a constant speed, and to the light beam (29 ') transmitted on the light-sensitive surface (26) of the information storage element is lowered under the control of a second part of the frequency-modulated signal, when the storage element (10) is moved at a constant speed. Method according to claim 1, characterized in that the frequency-modulated electrical signal is obtained by generating a first electrical signal 1, which has its information content 11 in the form of a voltage varying with the time format, and changing the voltage signal varying with time. to a frequency modulated electrical signal1 with its information content11 in the form of a carrier signal1, which has frequency changes with time corresponding to said voltage variations with time. 3. A method according to claim 1 or 2, characterized in that the light beam (29 ') is kept stationary and that the storage element (10) is moved at the constant speed relative to the stationary light beam (29'). Method according to any one of claims 1-3, characterized in that the control comprises utilizing the frequency modulated signal for varying the intensity of the light beam over a predetermined intensity, wherein the focused beam (29 ') changes the light-sensitive surface (26). , and below the predetermined intensity, where the focused beam (29 ') is not able to change the light-sensitive surface, said change being representative of the frequency-modulated signal. Method according to claim 4, characterized in that the first information signal has its information content in the form of a time-varying voltage signal suitable for presentation on a conventional television monitor, that a modulated asteroid is generated at said control. , collimated laser laser beam (29 ') of polarized monochromatic light arranged to sense the light-sensitive surface of the storage element, which surface is a thin, flat, opaque metal layer (26) having suitable physical properties to enable local heating depending on the laser writing beam (29 ') falling thereon, which heating causes local melting followed by retraction of molten material towards the perimeter of the molten area to leave a permanent aperture in the solidification of the metal. the thin metal layer, and that the control involves utilizing the frequency modulated signal to vary the intensity of the writing beam; t above the predetermined intensity, where the focused writing beam (29 ') melts the metal layer without evaporation, and below the predetermined intensity, where the focused writing beam (29') is not able to melt the metal surface (26). Method according to any one of claims 3-5, characterized in that the storage element (10) is disk-shaped and that the movement of the storage element involves generating a uniform rotational movement of the disk (10), synchronizing the rotational movement with translational movement of the light beam (29 ') to provide relative motion of the focused light beam radially across said surface (26) of the disk-shaped bearing member (10) to maintain a constant relationship between the rotational motion and the translational motion. Method according to claim 5, characterized in that the control comprises stabilizing the modulation level of the light beam (29 ') for operation between a predetermined higher light intensity and a predetermined lower light intensity, sensing at least a part (29 ") of the laser writing beam (29 ') after modulating the beam to generate an electrical feedback signal representing the intensity of the beam, and utilizing the feedback signal in the control to provide stabilization of the modulation level of the writing beam (29'). Method according to claim 7, characterized in that upon sensing at least a part of the writing beam (29 ') generates an electrical feedback signal, which is representative of the average intensity of the modulated writing beam, the operating level of the modulation of the light beam being stabilized in emitting the modulated write beam (29 ') at a substantially constant, average power level. Method according to any one of claims 5-8, characterized in that the control comprises rotation of the plane of polarization of the laser beam under the control of the frequency modulated signal, and linear polarization of the rotated beam to generate a modulated laser beam (29 '). corresponding to the frequency modulated signal. l0. Method according to one of Claims 7 to 9, characterized in that the control comprises selective setting of the average effeut level of the modulated writing beam (29 ') to a predetermined value. ll. A method according to any one of claims 7 to 10, characterized in that the control comprises amplifying the frequency modulated signal for generating corresponding drive signals to a Pocke1 cell device (68), that the the amplified frequency modulated signal is alternately connected to the Pocke1 cell device (68) and the feedback signal is electrically connected to the Pocke1 cell device (68). Apparatus for processing information in the form of a frequency modulated signal on an information storage element (10), each signal having its information content 11 in the form of a carrier signal with frequency changes with time representing the information, which information storage element (10) has a substrate (22) having a first surface (26) having markings (37, 38) which are representative of the information signal, the apparatus comprising a device (32) arranged to give the storage element a uniform movement, a light source (30) for generating of a light beam (29, 29 '), and an optical device (58, 60, 52) for guiding an optical path between the light source (30) and the first surface (26) of the storage element and for focusing the light beam on the first surface, k characterized in that the apparatus is arranged to store information in the form of a frequency modulated signal on an information storage element (10), and that the apparatus comprises a first device (16, 20) for providing an information signal for recording, that the first surface of the substrate has a light-sensitive coating (26) for preserving the markings (37, 38), that the light beam (29, 29 ') has a sufficiently high intensity to grow with the coating (26) while it is in motion and is located on the movable information storage element (10) and for changing the coating to preserve the markings (37, 38) representative of the information, and that the apparatus further comprises an optical path in the optical path (30) and the coating (26) on the storage element (10) located light intensity modulation unit (44), which is arranged to operate over an interval between a higher light transmitting state and a lower light transmitting state for the intensity modulation of the light beam with the light beam. The storage information, the light intensity modulating unit (44) being actuatable depending on the frequency modulated signal and is arranged to change between its higher light transmitting state and its lower light transmitting state during each period of the frequency modulated signal in order to modulate the light beam with the frequency modulated signal for storage, and that the and on the coating (26) the light focused on the optical device (52) is arranged to form said markings (37, 38) in the coating, which markings are representative of the frequency-modulated signal intended for storage. Apparatus according to claim 12, characterized in that the first device comprises a device (16) for generating a first information signal 1, which has its information content 11 in the form of a voltage which varies with time. And a frequency modulator device (20) which can be actuated depending on the device generating the first information signal, for converting the time-varying voltage signal into the frequency-modulated signal. l4. Apparatus according to claim 13, characterized in that the light intensity modulation unit (44) comprises an electrically controllable device (46) which can be actuated depending on the frequency modulator device (20) for varying the intensity of the light beam over a predetermined intensity, where the focused beam the beam (29 ') changes the coating (26), and below the predetermined intensity, where the focused beam (29') is not able to change the coating (26), said change being representative of the frequency modulated signal. Apparatus according to claim 14, characterized in that the first information signal has its information content in the form of a time-varying voltage signal, which is suitable for presentation on a conventional television monitor, that the light source (30) comprises a writing laser for generating a collimated writing beam with polarized monochromatic light, and that the substrate (22) of the information storage element forms a smooth, flat, rigid disk, on which said first surface is formed by a flat surface, that the coating is a thin, opaque metal layer (25), which has suitable physical properties to allow local heating in dependence on the writing beam (29 ') incident thereon, which heating causes local melting followed by retraction of the molten material towards the circumference of the molten area so as to subsequently solidify. leave a permanent opening in the thin metal layer (26) so that the electrically controllable device (46) can be actuated in depending on the frequency modulator device (20) for varying the intensity of the writing beam over the first predetermined intensity, where the focused beam (29 ') melts the metal layer (26) without lengthening it, and below the predetermined intensity, where the focused beam (29') does not is capable of melting the metal layer (26). l6. Apparatus according to claim 12, characterized in that the storage element (10) is disc-shaped, that the device for generating relative movement comprises a rotary drive device (32) for generating uniform rotational movement of the disc (10), that the apparatus further comprises a translational drive device (34) , which is synchronized with the rotary drive device (32) for relatively moving the focused light beam (29 ') radially over the first surface (26) of the disc-shaped storage element, and that an electrical synchronizing device (36) is arranged to maintain a constant relationship between the rotational movement and the translational movement. l7. Apparatus according to any one of claims 14 to 16, characterized in that the light intensity modulation unit (44) comprises a feedback device (48) for stabilizing the operating level of the electrically controllable device (46) for operation between a predetermined higher light intensity and a predetermined lower light intensity. wherein the light intensity modulating unit comprises a light sensing device (225) for sensing at least a part (29 ") of the light beam (29 ') emitted from the electrically controllable device (46) for generating a electrical feedback signal, which is representative of the intensity of the beam, and supply of the feedback signal to the electrically controllable device (46) for stabilizing its operating level. l8. Apparatus according to claim 17, characterized in that the light sensing device (225) is arranged to generate an electrical feedback signal representative of the average intensity of the light beam (29 '), the operating level of the light intensity modulation unit (44) being stabilized to emit the light beam. (29 ') at a substantially constant, average power level. l9. Apparatus according to any one of claims 12-28, characterized in that the optical device comprises an objective lens (52) and a hydrodynamic air storage device (54) for supporting the lens above the first surface of the information storage element (10). Apparatus according to claim 19, characterized in that the collimated light beam has substantially parallel light beams, that the objective lens (52) has an entrance aperture with a diameter larger than the diameter of the light beam as obtained from the light source (30), and that the optical device comprises a mirror device (58, 60) for deflecting the path of the light beam obtained by the light source, and a scattering lens (66) for scattering the substantially parallel light beam from the light source, so that the light beam at least fills the entrance aperture of the objective lens (52). Zl. Apparatus according to claim 14, characterized in that the light source (30) is arranged to generate a polarized laser beam, and that the electrically controllable device (46) comprises a device (68) for rotating the plane of polarization of the laser beam from the light source under the control of the frequency modulated signal, and a linear polarizer (70), the output of which is an intensity modulated laser beam (29 ') corresponding to the frequency modulated signal. Apparatus according to claim 18, characterized in that the feedback device (48) comprises a level setting device (236) arranged to selectively set the average power level of the light beam (29 ') to a predetermined value. Apparatus according to claim 18, characterized in that the electrically controllable device (46) comprises a Pockel cell driver (72) and a Pockel cell device (68), the Pockel cell driver (72) being operable depending on the the frequency modulated signal to generate corresponding drive signals to the Pockel cell device (68), and that the Pockel cell driver (72) is alternately connected to the Pockel cell device and that the stabilizing feedback device (48) is DC connected to the Pockel cell device.