WO1990011598A1

WO1990011598A1 - Optical recording and/or playback system with rotary scanner

Info

Publication number: WO1990011598A1
Application number: PCT/CA1990/000091
Authority: WO
Inventors: Ching Chu; G. John Adamson
Original assignee: Optical Recording Corporation
Priority date: 1989-03-17
Filing date: 1990-03-19
Publication date: 1990-10-04

Abstract

An optical system (10) is provided for reading and/or recording arcuate tracks (16a) of digital information from or on a record medium (16). The system includes a rotary scanner drum (32) supporting a light source (38). The light source is spaced from the axis of rotation (34) of the drum and generates an optical beam (18) having an intensity depending on whether data retrieval or recordal is desired. An objective lens assembly (36) is mounted on the drum and is positioned along the path of the optical beam between the light source and the record medium. A focus servo-unit (42) and a focus actuator (46) are also disposed on the drum adjacent the objective lens assembly (36) and function to adjust the position of the lens assembly axially with respect to the optical beam (18) so that the optical beam remains focussed on the record medium. A tracking servo-unit and a carriage actuator (22) are included in the system and are located remote from the scanner drum. The tracking servo-unit and carriage actuator (22) function to adjust the position of the record medium (16) in a direction substantially parallel to the longitudinal axis of the record medium to maintain the optical beam on the track of information being read therefrom. Record media for use in the above system are also provided.

Description

OPTICAL RECORDING AND/OR PLAYBACK SYSTEM WITH

ROTARY SCANNER

TECHNICAL FIELD

The present invention relates to an optical system and in particular to an optical recording and/or playback system.

BACKGROUND ART

Optical recording and/or playback systems for reading and/or recording information from discontinuous tracks on record media are known in the art. In systems such as that described in U.S. Patent 4,163,600 to Russell et al., the light source and the focus and tracking lens are remote from the rotating scanner drum. The focus and tracking lens functions to alter the path of the optical beam before the optical beam passes through the scanner drum optics to compensate for optical beam misalignment on the record medium.

However, by providing the focus and tracking lens remote from the scanner drum, problems exist in that additional optical components are required to direct the optical beam towards the record medium thereby increasing costs, reducing focus and tracking ranges and introducing off- axis errors in the optical beam path. Accordingly, there is a need for an improved optical system.

It is therefore an object of the present invention to obviate or mitigate the above disadvantages. DISCLOSURE OF INVENTION

According to the present invention there is provided an optical system for recovering tracks of information recorded on a record medium comprising: a light source for generating an optical beam; support means supporting at least one lens means; drive means for moving said support means to pass said lens means across said record medium in an arcuate path, said lens means receiving said optical beam and being moveable in response to focus error signals to maintain focus of said optical beam on said record medium; tracking means responsive to tracking error signals and altering the position of said record medium with respect to said optical beam to maintain said optical beam on information recorded on said record medium; and data recovery means receiving said optical beam after having impinged on said record medium and recovering said recorded information therefrom.

In another aspect of the present invention, there is provided a scanner for use in an optical system, said scanner supporting at least one lens means and being moveable about an axis to pass said lens means in an arcuate path across a record medium, said lens means being moveable on said scanner substantially parallel to said axis to adjust the focus of an optical beam during said pass.

In still yet another aspect of the present invention there is provided a record medium capable of having information optically recorded thereon, said record medium including a rigid frame member secured to a portion of at least one side of said medium.

Preferably, the support means is in the form of a scanner drum which is rotated about an axis. It is also preferred that the lens means is in the form of an objective lens assembly which is spaced from the axis of rotation of the drum. This design permits the lens assembly and hence the optical beam, to trace arcuate paths across the record medium. It is also preferred that the light source is mounted on the scanner drum adjacent the lens assembly to form a compact assembly. Preferably, the optical beam follows a path from the light source to the record medium that is substantially parallel to the axis of rotation of the drum.

Preferably, the scanner drum also supports an optical preamplifier which generates the focus and tracking error signals and recovers the recorded information. A focus servo-unit positioned adjacent the objective lens assembly receives the focus error signals directly from the pre-amplifier and adjusts the position of the objective lens assembly in response to these error signals. Preferably, a tracking servo-unit is positioned remote from the scanner drum and receives the tracking error signals from the optical pre-amplifier via an optical data link positioned along the axis of rotation of the scanner drum. The tracking servo-unit in turn adjusts the position of the record medium in response to the tracking error signals to maintain the optical beam on the track of information being read from the record medium. The present system provides a number of advantages in that since the objective lens assembly is not moved in the tracking direction (ie. perpendicular to the axis'of the optical beam), the design of the objective lens and light source assembly is simple.

Furthermore, since the objective lens assembly remains stationary in the tracking direction, centrifugal effects due to the scanner drum rotation have little or no effect on the objective lens assembly position. Moreover, since the focus and tracking actuators do not operate to move the same lens assembly as is done in conventional systems, resolution in the system is increased, since the motion of one of the actuators has little or no effect on the operation of the other actuator (ie. decreases crosstalk). The present system also increases focus and tracking range capabilities and hence, reduces mechanical tolerances.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings in which:

Figure 1 is a side view of an optical recording and/or playback system implementing a rotary scanner;

Figure 2a is a partial perspective view of a scanner drum used in the system illustrated in Figure 1;

Figure 2b is a top plan view of a record medium used in the system shown in Figure 1;

Figure 3 is a functional block diagram of a portion of the system shown in Figure 1;

Figure 4a is a circuit diagram of a portion of the diagram shown in Figure 3; Figure 4b is a sectional view of another portion of the system shown in Figure 1;

Figure 5 is a functional block diagram of another portion of the diagram shown in Figure 3; Figures 6a and 6b illustrate a position sensor and response curve therefor, used in the system shown in Figure 1;

Figures 7a and 7b illustrate response and position curves of components used in the system shown in Figure 1;

Figure 8 is a perspective view of another portion of the system shown in Figure 1;

Figure 9a is a side view of a record medium;

Figure 9b is a partial perspective view of an element of the medium shown in Figure 9a;

Figure 9c is an exploded perspective view of the medium shown in Figure 9a;

Figure 9d ia a perspective view of the medium illustrated in Figure 9a; Figures 10a and 10b are top and side views respectively of another record medium; and

Figures 11a and lib are top and side views of the medium illustrated in Figures 10a and 10b used in the system illustrated in Figure 1.

BEST MODES FOR CARRYING OUT THE INVENTION

Referring to the Figures, an optical recording and/or playback system 10 is shown. The system includes a carriage 14 disposed within a housing 12. The carriage 14 supports one side of a reflective record medium 6. The record medium 16 is capable of allowing arcuate tracks 16a of digital information to be recorded thereon or to be read therefrom using an optical beam 18. A carriage actuator 20 in the form of a linear motor is in communication with the carriage 14 and functions in a known manner to alter incrementably by a pre-determined distance the position of the record medium 16 along an axis "y". This allows successive tracks 16a of information recorded on the record medium to be scanned by the optical beam 18 as well as allows the optical beam 18 to remain on a recorded track 16a during a scan as will be described herein.

The carriage actuator 20 receives input signals from a tracking servo-unit and card motion function 22. The function 22 receives an input signal from a carriage position sensor 24 that is also in communication with the carriage 14. This allows the system to determine the position of the carriage 14 along the axis y.

A scanner drum 32 is located on the other side of the record medium 16 and rotates about an axis 34. A single objective lens assembly 36 is disposed on the drum and is spaced from the axis 34. The objective lens assembly 36 intermittently traces an arcuate path over the record medium 16 as the scanner drum 32 rotates. An optical read/write laser source 38 is mounted below the objective lens assembly 36 and generates the optical beam 18. The intensity of the optical beam generated by the laser source 38 is dependant on whether information is to be recorded on the record medium or read from the record medium. The laser source 38 and the objective lens assembly 36 are aligned so that the optical beam 18 follows a path through the objective lens assembly along the optical axis of the lens assembly towards the record medium 16. This path of the optical beam 18 is substantially parallel to the axis 34.

A photo-detector array 40 is also included and comprises six photo-detectors arranged in the manner shown in Figures 4a and 5, four 40a of which are used for focus and two 40b of which are used for tracking. The array 40 is disposed adjacent the laser source 38 and receives the reflected optical beam 18' from the record medium 16. Each of the photo-detectors 40a, 40b generates electrical signals upon reception of the optical beam 18' after it has been reflected from the record medium 16. The electrical signals generated by the photo-detectors 40a, 40b are conveyed to an optical preamplifier 41.

The preamplifier 41 is better illustrated in Figure 4a and is of a typical design. The preamplifier comprises a pair of subtractors 41a and 41b formed from differential amplifiers (diff-amps), three adders 41c, 41d and 41e respectively and two peak holders 41f and 41g. The preamplifier generates from the signals received from the photo-detectors, a tracking error voltage signal TE, a focus error voltage signal FE as well as retrieves a modulated signal HF which includes the high frequency digital data that are recorded in the form of the tracks 16a on the record medium 16.

The focus error signal FE is generated by adding separately the output of the diagonally located photo-detectors 40a via adders 41d and 41e. The two resulting sum signals are applied to a peak holder 41f and then subtracted via subtractor 41b to form the focus error signal FE. The tracking error signal TE is generated by passing the output signals of the photo- detectors 40b through a peak holder 41g and then subtracting the output signals via subtractor 41a. The modulated HF signal is recovered by taking the sum of the output signals generated by each photo-detector 40a, 40b using adder 41c. Since the operation of the pre¬ amplifier 41 is known in the art, the detailed operation thereof will not be discussed any further herein.

A focus servo-unit 42 receives the focus error signals FE from the preamplifier 41 as well as timing and predetermined operation signals from a microprocessor 52 via a digital to analog convertor (DAC) 43. The focus servo-unit 42 generates focus correction signals from the focus error and pre¬ determined operation signals and conveys the correction signals to a focus actuator 46. The focus actuator 46 is disposed adjacent the objective lens assembly 36 and 15 comprises a pair of coils that are coupled to the objective lens assembly 36. The coils function in a known manner to move the objective lens assembly 36 axially with respect to the optical beam 18 when energized by the focus correction signals to allow the 20 focal point of the optical beam 18 to be adjusted.

An analog to digital converter (ADC) 51 receives the tracking error signals TE from the pre¬ amplifier 41 and converts the signals into digital form 25 before they are conveyed to the microprocessor 52.

A focus position sensor 49 is also provided and communicates with the focus servo-unit 42, and the objective lens assembly 36. The sensor 49 provides information to the focus servo-unit 42 representing the position of the objective lens assembly 36 with respect to a default position as will be described herein.

An automatic gain control circuit (AGC) and phase lock loop (PLL) 50 receives the modulated HF signal outputted by amplifier 41c so that the recorded digital information can be retrieved when scanned by the optical beam 18. The digital output of the AGC circuit and PLL 50 is applied to the microprocessor 52 before being optically transmitted along an optical data link 54. As is well known in the art, the optical data link includes electrical to optical and optical to electrical converters as well as a glass fibre.

A laser drive circuit 56 also receives input signals from the microprocessor 52 and provides power to the laser source 38 as well a biasing voltage for the photo-detectors 40a, 40b in response to these signals. The microprocessor 52 also receives input signals from a timing logic function 58a so that the digital information outputted and received by the microprocessor 52 is clocked at appropriate intervals.

A rotary switching transformer 60 is disposed within an annular channel formed in the scanner drum 32 and surrounds the optical data link 54. The rotary switching transformer 60 is connected to a switching power supply 62 at its primary terminals and to the various components disposed on the drum 32 at its secondary terminal. The transformer 60 provides isolated power to the components on the drum 32 and is used to reduce noise in the system 10 typically 25 encountered when using systems implementing brushes to convey electrical power to a rotating component.

The rotary transformer 60 is better illustrated in Figure 4b and as can be seen, the transformer secondary 60a comprises a magnetic core 60b surrounded by coils 60c. The secondary 60a is mounted on the drum 32 and is rotatable therewith. The transformer primary 60d is stationary and is disposed directly below the secondary 60a. The primary 60d has a similar configuration as the secondary and receives a 12^v supply voltage across its terminals from the power supply 62. The secondary 60a in turn is energized when the primary is energized even while the drum 32 rotates to allow the components disposed on the drum 32 to be supplied with power.

A brushless DC motor 64 is provided on the scanner drum 32 and functions to rotate the scanner drum 32 at a substantially constant speed. The motor 64 is driven by a motor driver 66 that receives information from a second microprocessor 68 as well as from an encoder 70. The microprocessor 68 is also in communication with the optical data link 54 so that information can be transferred between the two microprocessors 68 and 52 and so that the tracking error signals can be conveyed to the tracking servo-unit 22.

An index mark 72 as well as a plurality of closely spaced position marks are located on the outer surface of the scanner drum 32. The encoder 70 which is spaced from the scanner drum 32 detects these marks via a light source, light detector and counter (not shown) and provides signals to a timing logic function 58b. The timing function 58b provides clocking information to the microprocessor 68 in response to the signals received from the encoder 70. The timing function 58a disposed on the scanner drum 32 communicates with the timing function 58b so that the components disposed on the drum and those located remote from the drum 32 remain in sync.

A read/write function 74 is in communication with the microprocessor 68. The function 74 provides instructions to the microprocessor 68 that are used by the system 10 to control the operation of the laser source 38. A small computer system interface (SCSI) 76 communicates with the microprocessor 68 and allows data transfer between the microprocessor 68 and a user micro¬ computer 78.

Referring now to Figure 5, the focus servo- unit is better illustrated. As can be seen, the focus servo-unit includes a compensator 42c receiving the output of diff-amp or subtractor 41b. A focus-servo control logic function 42d also receives the output of the diff-amp 41b. A gain control circuit 42e receives the output of the compensator 42c and provides an input signal to an analog switch 42f. The control logic function 42d receives input timing signals from the microprocessor 52 via the DAC 43 over control lines 42g.

The control logic function provides two signals to a ramp generator 42h, a control signal to two other analog switches 42i and 42j respectively as well as a signal to a sample and hold circuit 42k. The output of the ramp generator 42h is conveyed to the analog switch 42i. The sample and hold circuit 42k also receives an input signal from a diff-amp 421 that is connected to the focus position sensor 49. The sample and hold circuit 42k provide an output signal to the analog switch 42j representing the position of the objective lens assembly 36 at the best focus position during its previous pass over the record medium. The output signal passed by the analog switch 42j is combined with a focus demand signal that is supplied to a focus demand conductor 42m from the microprocessor 52 via the DAC 43. The resulting signal in turn is fed to a summing block 42n. The summing block 42n also receives the output of analog switch 42i and the inverted output of analog switch 42f and forms a resultant signal that is equivalent to the sum of the three input signals. The resultant signal is then applied to a power amplifier 42o wherein an appropriate correction signal is formed which is applied to the focus actuator 46.

The focus position sensor 49 is illustrated in

Figures 6a and 6b and as can be seen includes a light source 49a mounted on the scanner drum 32 adjacent the objective lens assembly 36. A mirror 49b is secured to the objective lens assembly 36 and reflects a light beam 49c that is generated by the light source 49a towards a set of photo-detectors 49d. The photo-detectors 49d provide an output signal having a linear response as shown in Figure 6b. The magnitude of the output signal is determined by the axial movement of the objective lens assembly 36 from its rest position. As mentioned previously, the output signals from the position sensor 49 are conveyed to the focus servo-unit 42 to allow the position of the objective lens assembly to be fixed when the objective lens assembly 36 is remote from the record medium 16.

The tracking servo-unit and card motion function 22 is software controlled and performed by the - microprocessor 68. The microprocessor uses software to scale the tracking error signals outputted by diff-amp 41a by the factor:

TE cos (0)

wherein TE is the tracking error signal and 0 is the angle of rotation of the drum 32 from the leading edge of the record medium. The resulting scaled tracking error signals TE, are applied to the linear motor 20 to effect the proper tracking operation.

Referring now to Figure 8, the card carriage 14 and carriage actuator 20 are better illustrated. As can be seen, the carriage 14 includes a frame assembly 14a provided with a slot 14b for receiving the record medium 16. The lower surface of the assembly 14a is open to allow the optical beam to impinge on the medium 16 when it is supported by the carriage 14. The linear motor 20 is located on the other side of the carriage 14 and moves along a track in the Y direction when it is energized via tracking correction or card motion signals.

The operation of the system 10 will now be described with reference to the Figures. When it is desired to read a track 16a of information from the record medium 16 that is supported by the carriage 14, the system 10 is powered up. Thereafter, the microprocessor 68 conveys information to the motor driver 66 which in turn energizes the motor 64 so that the drum 32 is rotated at a substantially constant speed. As the drum rotates, the encoder 70 detects the index mark and position marks and counts the marks so that the position of the laser source 38 and objective lens assembly 36 with respect to the carriage 14 can be determined by the microprocessor 68.

The encoder 70 while doing this also provides a feedback signal to the motor driver 66 so that the speed of rotation of the drum 32 can be monitored and maintained at the desired constant speed. The encoder 70 also provides clock pulses to the timing generator 58b. The timing generator 58b in turn uses the clock pulses to provide timing pulses to the microprocessor 68 so that the information therein is clocked properly as well as to provide timing signals to the timing generator 58a on the drum 32. At the same time, the power supply 62 is also energized via the 12^v supply voltage so that the supply voltage can be conveyed to the components disposed on the drum 32 via the transformer 60.

After completing this, the read/write function

74 is set to the read mode and appropriate instruction signals are conveyed to the microprocessor 68. The microprocessor 68 in turn conveys the instruction signals along the optical data link 54 to the microprocessor 52. The microprocessor 52 upon receiving the instruction signals supplies control signals to the laser drive circuit 56 which conditions the laser source 38 to generate an optical beam 18 having an intensity suitable for reading digital information from the recorded medium 16. If it is desired to write information on the record medium 16, the read/write function 74 is set to a write mode. Similarly, control information is conveyed to the laser drive circuit 56 in the same manner described above. The drive circuit 56 in this mode conditions the laser source 38 to generate an optical beam having an appropriate intensity for recording digital information on the record medium.

When recovering or writing data from or on the record medium 16, the system 10 employs three functions, these being focussing, profiling and tracking. The focus servo-unit 42, is used to perform the focus function. The position sensor 49 is employed to compliment the focus function. The profiling function is used to position the record medium 36 in pre-set positions when information is to be recorded on the record medium 16 so that the optical beam impinges on the record medium in a desired manner. Typically, the profiling is used so that the optical beam 18 is directed onto the medium 16 such that it follows a path similar in shape to the shape of the last written track on the medium. This of course, increases memory storage capabilities in that the profiling function allows the track to track separation distance to be reduced.

Since the objective lens assembly and laser source are removed from the record medium during a portion of the rotation of the scanner drum, the focus servo-unit 42 does not receive any focus error signals from the preamplifier 41 while it is remote from the record medium 16. This places the focus servo-unit 42 in an open-loop condition, since feedback from the pre¬ amplifier 41 is removed. However, the focus servo-unit must assume a closed-loop condition as soon as the optical beam 18 hits the leading edge of the record medium 16 and must re-gain focus on the record medium 16 quickly if recorded information on the medium is to be retrieved.

This on/off or equivalently closing and opening of the focus servo-unit 42 dictates the hardware and software requirements thereof. When the objective lens assembly 36 is in an off medium position, the focus position sensor 49 output signals are used. In particular, when the assembly 36 is remote from the record medium 16 and focus error signals are not received from the preamplifier 41, a closed-loop condition is formed between the servo-unit 42, focus actuator 46, objective lens assembly 36 and the position sensor 49.

In particular, when the assembly 36 is remote from the medium 16, the microprocessor 52 detects this condition from the output of the timing function 58a. The microprocessor 52 in turn conveys signals to the control logic 42d via the DAC 43 and control lines 42g. The logic 42d in turn opens analog switches 42f and 42i and closes analog switch 42 . At this time, the logic

42d provides instructions to the sample and hold circuit 42k causing it to supply the signal stored therein to the summing block 42n via the switch 42j. The signal stored in the sample and hold circuit 42k represents the position of the assembly 36 at its best focus position (PE=0) during the previous pass over the record medium. The best focus position signal is combined with a default assembly position demand signal, which is typically zero volts, that is received from the microprocessor 52 via DAC 43 and conductor 42m. The position demand signal is set at a level so that the objective lens assembly 36 assumes a default position when no other signals are received by the servo-unit 42.

The amplifier 42o receives the output signal generated by the summing block 42n. The amplifier 42o boosts the signal received from the summing block 42n and in turn conveys the amplified signal to the focus actuator 46 so that the assembly 36 is moved axially with respect to the path of the optical beam 18 to the best focus position during .its off medium travel.

When the objective lens assembly 36 approaches the record medium, the microprocessor 52 is supplied with appropriate timing information from the encoder 70 and timing function 58a. When the assembly 36 reaches a predetermined number of encoder marks from the leading edge of the medium, the switch 42j is opened and the switch 42i is closed via the logic function 42d. At this time, the generator 42h outputs a ramp voltage which is conveyed to the summing block 42n via the switch 42i. The ramp voltage is combined with the focus demand signal and then conveyed to the amplifier 42o. The amplifier 42o in turn supplies the amplified ramp voltage to the focus actuator 46 which moves the assembly 36 axially at a constant rate with respect to the optical beam 18. While this occurs, the focus error signal generated by the preamplifier 41 is monitored and the position sensor 49 output signal is sampled.

When the focus error signal reaches the best focus position as shown in Figure 7b, the position of objective lens assembly 36 at the best focus position is stored in the sample of hold circuit 42k. This best focus signal is generated by the diff-amp 421 in response to the output of the photo-detectors 49d included in the position sensor.

If the optical beam 18 is not focussed properly on the record medium 16 immediately after it impinges on recorded information, the track 16a to be recovered is re-read. While the assembly 36 is removed from the medium, the system uses the new best focus position signal stored in the sample and hold circuit 42k to move the assembly 36 to a position closer to the optimum focus position while it is removed from the medium 16. When the assembly 36 approaches the medium 16 again, the assembly 36 is driven by the ramp voltage. However, the ramp voltage is applied to the summing block when the assembly 36 is in a position closer to the edge of the medium so that focus is achieved more quickly. Hence, subsequent scans of the optical beam 18 on the medium 16 require shorter times to ramp to the best focus position. This allows the focus of the optical beam 18 on the medium 16 to be achieved faster and allows all of the information recorded on the track to be recovered. It should be apparent that the ramp voltage is applied to the assembly in a manner so that the assembly does not achieve the best focus position for the track to be read prior to the optical beam impinging on the track. This ensures that the best focus position is attained as the assembly is moved by the ramp voltage.

Once a track is to be read and focus of the optical beam 18 on the record medium 16 has been achieved using the ramp voltage and best focus pre- positioning quickly enough to recover all of the recorded data track, the focus servo-unit 42 relies on the focus error signals generated by the preamplifier 41 to maintain proper focus of the optical beam 18 on the medium 16. Accordingly, as soon as the optical beam impinges on the record medium 16, the switch 42f is closed and the switches 421 and 42j are opened.

During the time that focus of the optical beam 18 on the record medium 16 is being achieved in the above-mentioned manner, the tracking function operates to maintain the optical beam on the track of the recorded information being read. As the optical beam 18 begins a pass over the medium 16, the tracking error signals generated by the preamplifier 41 are digitized via ADC 51 and conveyed to the microprocessor 52. The microprocessor 52 in turn transmits the error signals to the microprocessor 68 via the optical data link 54. At this time, the timing generator 58b conveys information concerning the position of the laser source 38 with respect to the edge of the medium 16 associated with each of the tracking error signals. The position information generated by the timing generator 58b is angular information representing the amount of rotation of the scanner drum 32 from the edge of the record medium.

The microprocessor 68 uses the angular information associated with the tracking error signals and scales the tracking error signals by a factor equal to

TE cos (0) wherein TE is the tracking error signal generated by diff-amp 41a and wherein 0 is the angle of rotation of the scanner drum 32 from the edge of the record medium. The tracking servo-unit receives the scaled tracking error signals and in turn generates tracking correction signals which are conveyed to the tracking servo-unit 22, the servo-unit 22 being of any conventional form. The correction signals are then conveyed to an amplifier circuit prior to being fed to the linear motor 20. When the linear motor 20 receives the output from the amplifier circuit, it is energized causing it to move thereby moving the carriage 14. The movement of the carriage is in a direction to align the optical beam 18 on the track of information to be read to reduce the tracking error signal generated by the preamplifier 41 to substantially zero-volts. Since, the preamplifier 41 continuously generates tracking error signals in response to the output of the photo-detectors 40b, the position of the record medium is continuously adjusted via this closed-loop circuit during the entire scan of the optical beam 18 across the record medium 16.

Once focus and tracking of the optical beam is locked, the output signals of the adder 41c which includes the recorded digital information are demodulated and digitized by the AGC and PLL circuit 50 prior to being conveyed to the microprocessor 52. From the microprocessor, the recorded data are transmitted across the optical data link 54 and received by the microprocessor 68. The recovered digital information can then be transferred to the user computer 78 via the interface 76 so that the retrieved information may be used in other processes. It should be realized that if it is desired to read a different track of information from the record medium 16, the carriage actuator 20 is energized via the unit 22 so that the record medium 16 is advanced by the predetermined increment in the appropriate direction. This operation allows the optical beam 18 to impinge substantially on the proper recorded track of information to be retrieved.

When it is desired to write a track of information on the record medium, the read/write function 74 is set accordingly so that the laser source 38 is properly conditioned to generate an optical beam of the correct intensity. Prior to writing a track, the last written track of information written on the medium is read in the manner described above. During this time the position of the carriage 14 at the start and end of the track being read are monitored by the microprocessor 68. The microprocessor 68 interpolates these carriage positions using a typical arc followed by the assembly 36 over the medium and forms profiling signals therefrom. Once the profiling signal have been calculated, the carriage is moved so that a track of information can be recorded on a blank portion of the medium. As the assembly 36 begins a pass across the medium 16, the profiling signals are conveyed to the tracking servo-unit which alters the position of the carriage 14 and hence the medium 16 in the above described manner to attempt to ensure that the track of information to be written is substantially the same shape as the last written track.

Although the system 10 has been described as having a single light source and objective lens assembly, it should be realized that a plurality of sources 38 and objective lens assemblies 36 can be disposed on the rotating scanner drum 32. In this manner, each successive optical head and objective lens assembly will pass over the record medium 16 to enable tracks of information to be recorded on the record medium and to be retrieved from the record medium at a faster rate.

Although the focus servo-unit has been described as using both the ramp voltage generator and the sample and hold circuit, these two functions may be used independently. If desired, the ramp generator circuit can be eliminated. If this is done, the best focus position signal stored in the sample and hold circuit 42k is used in conjunction with the position sensor 49 to preposition the assembly 36 during its off-medium condition. Thus, the assembly 36 is maintained in the best focus position for the previous pass of the optical beam 18 during the off-medium condition. When the assembly 36 begins a pass over the medium, the analog switch 42j is opened and the analog switch 42f is closed to allow the focus error signals to 20 be used. Since the lens assembly 36 is held in a previous best focus position during off-medium conditions, the time to reach focus when the assembly 36 reaches the medium is small. This is due to the fact that the best focus position does not typically deviate 25 greatly between passes of the lens assembly 36 over the medium 16.

As an alternative, the sample and hold circuit and focus position sensor can be removed and the ramp generator circuit can be used by itself to obtain quick focus. When using the ramp generator circuit independently, the amount of rotation of the drum 32 is monitored from the time at which the analog switch 42i is closed and the assembly 36 is driven by the ramp voltage. It if is determined that focus is achieved after the beam 18 has passed a distance over the medium, the time at which the ramp is applied to the focus actuator 46 is altered for the next pass so that the assembly 36 attains the best focus position closer to the leading edge of the medium. This ensures that focus of the optical beam on the medium is attained quickly.

Referring now to Figures 9a to 9d, a preferred record medium 100 in the form of a card for use in the system 10 is shown. The record medium 100 comprises a plastic substrate 102 having a surface 104 which allows digital information to be recorded thereon. A metallic frame 106 having a ledge 108 is disposed along the perimeter of the medium 100 in a manner so that the ledge rests on the outer portion of the surface 104. A second plastic layer 110 rests on the ledge 108 and is spaced from the substrate 102. The frame 106 and ledge 108 function to reduce wear of the record medium 100 during its use in the system 10 and offer better card registration. The ledge 108 also allows an air gap 112 to be created in the card medium while providing a 20 border for sealing. The design yields several advantages in both card registration and guide control during card manufacturing processes.

To produce the card 100, the frame 106 is firstly formed using a press-die operation. Thereafter, the substrate 102 is glued to the press-died frame 106. Following this, the second layer 110 is placed on the other side of the press-died frame 106 in situ to create the record medium.

Figures 10a and 10b illustrate another record medium 200 for use in the system 10. This medium 200 is also formed from plastic material suitable for optical recording and playback and includes a wire frame 202 disposed along the entire outside edge of the medium. The wire frame 202 is preferably formed from ferro¬ magnetic material such as steel alloy spring wire thereby allowing it to be easily picked up or moved by a permanent magnet or electro-magnet. The medium 200 can be easily manufactured either by plastic heat modelling or by using an adhesion method. By providing the metal wire frame 202 on the medium, the medium is provided with a smooth and rigid outer surface which provides a repeatable registration reference edge.

The metal frame 202 also functions to protect the record medium 200 from edge-wear and lamination and surface scratches if the frame 202 is slightly larger than the thickness of the medium or if the frame 202 is adhered to the card so that it extends above the side of the medium receiving the optical beam. The metal frame 202 also reduces card deformation and hermetic sealing problems as well as facilitates insertion of the medium into the carriage and guide control once the medium is in the carriage 14.

As is illustrated in Figures 11a and lib by using a ferromagnetic wire frame 202, the carriage 14 and carriage actuator 20 previously described can be substituted for three magnetic wheels 210. The wheels 210 engage with the wire frame 202 to hold the medium 16 within the housing 12. A motor 212 is coupled to one of the wheels and rotates it so that the medium may be advanced along the Y-axis in response to tracking correction signals or card motion signals.

The present system and recording medium therefor provide advantages in that they reduce power requirements in the optical system and increase the resolution therein.

It should be apparent to one skilled in the art that various modifications can be made to the present devices without departing from the scope of the invention.

Claims

We claim:

1. An optical system comprising: a light source for generating an optical beam; support means supporting at least one lens means; drive means for moving said support means to pass said lens means across said record medium in an arcuate path, said lens means receiving said optical beam and being moveable in response to focus error signals to maintain focus of said optical beam on said record medium; tracking means responsive to tracking error signals and altering the position of said record medium with respect to said optical beam to maintain said optical beam on information recorded on said record medium; and data recovery means receiving said optical beam after having impinged on said record medium and recovering said recorded information therefrom.

2. The optical system as defined in Claim 1 wherein said support means is moveable about an axis, said light source and said lens means being spaced from said axis and being supported on said drum.

3. The optical system as defined in Claim 2 wherein said lens means comprises an objective lens assembly, said objective lens assembly and said light source being aligned so that said optical beam passes through said objective lens assembly along its optical axis and impinges on said record medium following a path substantially parallel to said axis.

4. The optical system as defined in Claim 3 further comprising a focus servo-unit and a focus actuator disposed on said support means, said focus servo-unit receiving said focus error signals and supplying focus correction signals to said focus actuator, said focus actuator including a pair of coils connected to said objective lens assembly, said coils being for moving said objective lens assembly axially with respect to said optical beam upon receipt of said focus correction signals.

5. The optical system as defined in claim 4 wherein said support means is in the form of a rotating scanner drum, said drum rotating about said axis.

6. The optical system as defined in Claim 5 wherein said tracking means comprises a tracking servo- unit and a carriage actuator, said record medium being supported by a carriage, said tracking servo-unit receiving said tracking error signals and supplying tracking correction signals to said carriage actuator, said carriage actuator moving said carriage upon receipt of said correction signals thereby adjusting the position of said record medium.

7. The optical system as defined in Claim 1 wherein said tracking means comprises a tracking servo- unit and a carriage actuator, said record medium being supported by a carriage, said tracking servo-unit receiving said tracking error signals and supplying tracking correction signals to said carriage actuator, said carriage actuator moving said carriage upon receipt of said correction signals to adjust the position of said record medium.

8. The optical system as defined in Claim 7 further comprising processing means receiving said tracking signals prior to being applied to said tracking servo-unit and scaling said signals by a factor equal to

TE cos (0)

wherein TE is the tracking error signal and wherein 0 is the angle of rotation of said lens means over said record medium beginning from the leading edge of said record medium.

9. The optical system as defined in Claim 8 further including light detection means disposed on said support means and receiving said optical beam from said record medium, said light detection means comprising an optical pre-amplifier receiving the output from said light detection means and generating therefrom said focus and tracking error signals as well as retrieving said recorded information thereby constituting said data recovery means.

10. The optical system as defined in claim 9 wherein said support means is in the form of a rotating scanner drum, said scanner drum rotating about said axis.

11. The optical system as defined in Claim 10 further comprising an optical data link extending through said scanner drum along said axis and being in communication with said optical pre-amplifier, said optical data link providing a path for said tracking error signal to said processing means.

12. The optical system as defined in Claim 11 wherein said lens means comprises an objective lens assembly, said objective lens assembly and said light source being aligned so that said optical beam passes through said objective lens assembly along its optical axis and impinges on said record medium following a path substantially parallel to said axis.

13. The optical system as defined in Claim 12 further comprising a focus servo-unit and a focus actuator disposed on said support means, said focus servo-unit receiving said focus error signals and supplying focus correction signals to said focus actuator, said focus actuator including a pair of coils connected to said objective lens assembly, said coils being for moving said objective lens assembly axially with respect to said optical beam upon receipt of said focus correction signals.

14. The optical system as defined in Claim 13 further comprising a rotary transformer in communication with a power supply, said transformer supplying power to said light source, said optical pre-amplifier and said focus servo-unit.

15. The optical system as defined in Claim 14 further comprising control means for detecting the position of said light source with respect to said record medium.

16. The optical system as defined in Claim 15 wherein said control means comprises a controller and a position mark detector located remote from said scanner drum, said scanner drum having a plurality of position marks located thereon, said position mark detector detecting successive passes of said position marks and providing signals to said controller indicating the position of said light source with respect to said record medium, said controller receiving said signals and controlling the operation of said transformer and providing information to said processing means representing the angle 0.

17. The optical system as defined in Claim 16 further comprising a computer interface, said recorded information being conveyed to said control means via said optical data link to allow the transfer thereof to said interface.

18. The optical system as defined in Claim 1 wherein said light source is operable in two modes, in said first mode, said light source generating an optical read beam to facilitate recovery of said recorded information and in said second mode, said light source generating an optical beam to allow information to be recorded on said record medium.

19. A scanner for use in an optical system, said scanner supporting at least one lens means and being moveable about an axis to pass said lens means in an arcuate path across a record medium, said lens means being moveable on said scanner substantially parallel to said axis to adjust the focus of an optical beam during said pass.

20. A scanner as defined in claim 19, where said lens means is moveable along a single axis parallel to said axis.

21. A scanner as defined in claim 20, wherein said scanner further supports a focus actuator in communication with said lens means, said focus actuator being operable to move said lens means along said single axis in response to focus error correction signals.

22. A scanner as defined in claim 21 wherein said scanner is in the form of a rotating scanner drum, said single axis being parallel to the axis of rotation of said scanner drum.

23. A scanner as defined in claim 22 further supporting a light source disposed above said lens means, said light source being positioned so that said optical beam is co-incident with the optical axis of said lens means.

24. A scanner as defined in claim 23 wherein said lens means comprises an objective lens assembly.

25. A record medium capable of having information optically recorded thereon, said record medium including a rigid frame member secured to a portion of at least one side of said medium.

26. A record medium as defined in Claim 25 wherein said frame member extends along the entire outer periphery of said record medium.

27. A record medium as defined in Claim 26 wherein said frame is formed from a thin ferro-magnetic wire.

28. A record medium as defined in Claim 27 wherein said frame extends above the light incident side of said record medium.

29. A record medium as defined in Claim 28 wherein said frame comprises first and second perpendicular portions to define a backing and a ledge respectively and said record medium includes first and second layers, said ledge being secured between said first and said second layers and said backing extending outward from said medium.

30. A record medium as defined in Claim 29 wherein a portion of said ledge is removed to provide a gap between said first and second layers.