MXPA99005696A - Method and apparatus for controlling the linear velocity between an optical head and a rotation disk - Google Patents

Abstract

An improved method and apparatus for maintaining a recording head (26)in an optical recording system at a constant linear velocity relative to a rotatable disk support (10), a rotation controller (40) uses a cumulative measure of rotation to determine an angular velocity of the rotating disk support (10) necessary to maintain a constant linear velocity.

Description

METHOD AND APPARATUS FOR CONTROLLING LINEAR SPEED BETWEEN AN OPTICAL HEAD AND A ROTATION DISC FIELD OF THE INVENTION The present invention is directed to the field of disc recording systems, and more specifically to a method and apparatus for controlling linear velocity in the optical recording system.

BACKGROUND OF THE INVENTION Optical recording systems for devices, such as the common compact disc (CD), typically have an optical recording head located very close to a rotatable disk that supports the recording medium. When the disc rotates, an information signal is recorded in the recording medium by a transducer in the recording head while the recording head moves in a substantially radial direction along the surface of the recording medium. The first recording systems were instrumented with the recording medium rotatable at a constant angular velocity. The constant angular velocity systems can be easily instrumented because a motor that rotates the recording medium at a constant angular velocity does not require a complex speed control once the chosen motor speed has been reached. A problem associated with constant angular velocity systems is the inefficient way in which data is stored. The density of the data recorded on the disk at a constant angular velocity varies according to the position of the optical recording head. As the recording head approaches the outer perimeter of the disc, the linear velocity actually increases. As a result, the data that is stored closest to the perimeter of the disk takes more space than the data that is stored closest to the center of the disk. A more uniform storage density must be achieved by keeping the recording head at a constant linear velocity relative to the rotatable disk holder during recording. However, a price is paid on the added complexity of the constant linear velocity systems. To maintain a constant linear velocity, the angular velocity of the rotatable recording medium must be updated repeatedly in accordance with changes in the position of the recording head. Constant linear velocity systems are more complicated because information must be recorded in the regions of the disk having dimensions of the order of microns. Current constant linear speed systems have limited accuracy. A current implementation follows the radial position of the optical head in relation to the disc holder and updates the angular velocity of the disc holder in relation to changes in radial position. This approach has a precision limited by the relatively short travel distance in the radial direction. Other systems use position indicators placed on the substrate of the recording medium to update the angular velocity. The optical recording head detects the position indicators during the recording process. When each indicator is detected, the system establishes the angular velocity to maintain the constant linear velocity relative to the radial position. Despite the improved accuracy, there are some disadvantages to using the position indicators. First, while developing new optical formats that use smaller recording points, the position indicators become less practical. Furthermore, the preparation of the recording means before the recording step further complicates the manufacturing process. In addition, the technique may not be suitable for all optical formats. It would be preferable to implement a constant linear velocity scheme in which the angular velocity could be updated on a more continuous basis than current systems. It would also be preferable to implement a constant linear velocity scheme without affecting the recording medium in the process.

BRIEF DESCRIPTION OF THE INVENTION In view of the foregoing, the present invention is directed to improving an optical recording system including an optical recording head and a rotatable disk holder located very close to the optical recording head. The rotatable disk holder is movable along a first path comprising a radial component from an initial radial position by a translation motor. A disk motor coupled to the disk holder rotates the disk holder at an eligible angular velocity. A motion sensor is coupled to the disk holder and operates to generate a sensor signal indicative of the rotation of the disk holder. The improvement includes an operational translation driver to move e! disk support along the first path. The improvement also includes a rotation controller that responds to the sensor signal and operative to determine a cumulative measure of rotation. The rotation controller sets the angular velocity of the disk motor as a function of the cumulative rotation measurement to control the linear velocity between the recording head and the rotatable disk. In another aspect of the present invention, there is provided a method for maintaining a rotatable disk holder movably radially at a constant linear velocity relative to an optical recording head with the rotatable disk rotating at an eligible angular velocity. The method includes the step of moving the rotatable disk from an initial radial position along a radial path to an initial radial velocity. The method further includes the step of rotating the rotatable disk at an initial angular velocity. The cumulative measure of rotation of the rotatable disk is determined and the angular velocity of the rotatable disk is updated in response to the cumulative rotation measurement to maintain the line speed! constant.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a block diagram of a preferred embodiment of the present invention; Figure 2 is a block diagram of an alternative embodiment of the present invention; Figures 3A and 3B illustrate a spiral path substantially defined by an optical recording head during the operation of the system illustrated in Figure 1; Figure 4 is a preferred embodiment of the translation and rotation movement controllers in the optical recording system of Figure 1; Figure 5 is an alternative embodiment of translation and rotation movement controllers in the system of Figure 1; and Figures 6A and 6B are flowcharts that describe a method for maintaining a constant linear velocity in the optical recording system of Figure 1.

DETAILED DESCRIPTION OF CURRENTLY PREFERRED MODALITIES Preferred embodiments of the invention will be described with reference to the drawings, where the numbers refer to the parts. Preferred embodiments of the present invention provide an improved optical recording system that maintains a recording head at a constant linear velocity relative to a rotating disk. Although the embodiments of the present invention are in optical recording systems, it should be understood that the embodiments of the present invention can be adapted to any data storage system in which the transducer mounted on a head scrutinizes a rotation means to a linear speed chosen. Figure 1 is a block diagram of a preferred embodiment of an optical recording system in which a rotatable disk holder 10 moves in a linear direction close to an optical recording head 26. The translation movement of the disk holder 10 rotatable in combination with the rotation of the disk holder 10 causes the recording head 26 to scan at a constant linear velocity relative to the rotatable disk holder 10. The disk location system 30 includes a rotation controller 40., a rotational servomechanism 18, a disk motor 16 and a motion sensor 12. The rotation controller 40 generates a rotation control signal R on line 58, which connects the rotation controller 40 with the rotation servomechanism. The rotary servomechanism 18 detects the rotation control signal R and generates the motor control signals on the line 17. The motor control signals on the line 17 guide the disk motor 16 in accordance with the signal R of rotation control. The rotation controller 40 is connected to the motion sensor 12 by a line 14. The motion sensor 12 generates a sensor signal S on the line 14 to provide the rotation controller 40 with an indication of the current angular velocity, as well as a rotational displacement measurement of the rotatable disk holder 10. In a preferred embodiment, the motion sensor 12 includes a tachometer, such as an optical encoder with a transducer that generates a flow of electronic pulses such as the sensor signal S. The frequency of the sensor signal S is indicative of the angular velocity of the rotatable disk holder 10. The pulse count of the sensor signal S is indicative of the rotation displacement of the disk holder 10. In a preferred embodiment, a revolution The complete disk holder 10 is indicated by 525 pulses of the sensor signal S. The rotation controller 40 determines a cumulative measure of rotation of the rotatable disk holder 10 each time an incremental rotation shift is indicated by the sensor signal S. The rotation controller 40 uses the cumulative rotation measurement to determine and update the angular velocity that the rotatable disk holder 10 will maintain at a constant linear velocity relative to the recording head 26. The rotation controller 40 then generates a signal R of rotation control indicative of an updated angular velocity. The rotation control signal R preferably consists of a flow of digital pulses with a frequency value indicative of the angular velocity. The rotation control signal R is detected by the rotation servomechanism 18 which translates the signal R of the rotation control into motor signals directing the motor of the disk 16 according to the signal R of rotation control. The rotation servomechanism 18 also detects the sensor signal S and uses the sensor signal S as feedback. In a preferred embodiment, the rotational servomechanism 18 will direct the disk motor 16 at one revolution for every 525 pulses received as a rotation control signal R. An example of a rotating servomechanism 18 that can be used in a preferred embodiment includes the BDC 0610 model from MFM Technology, Inc. The disk motor 16 includes a motor shaft 15 connected to the rotatable disk holder 10. The motion sensor 12 it is connected to the rotatable system to detect the rotation of the disk holder 10. Although the sensor 12 in figure 1 is illustrated mounted on the arrow of the motor 15, the motion sensor can be connected to any part suitable for the rotatable mechanism. The disk motor 16 preferably includes a three-phase, phase-locked direct current motor. Other motors, such as stepper motors, can also be used since they can maintain the accuracy required by the optical recording system. The location system of the recording head 32 includes a translation controller 60, a translation servomechanism 22, a translation motor 20 and a linear motor arrow 24. The signal! R of contro! The rotation system generated by the disk location system 30 is detected by the translation controller 60. The translation controller 60 then generates a translation control signal T on the line 28 indicative of a translation speed in which the support The rotatable disk 10 must be moved to maintain the optical head 26 located along the first radial path 21. The translation servomechanism 22 detects the translation control signal T and guides the translation motor 20 at a speed corresponding to the signal ! T of contro! Translation The translation motor 20 guides the linear motor shaft 24 to provide the translation of the rotatable disk holder 10 along the radial path 21. In a preferred embodiment, the translation motor 20 may include a linear motor and the servo motor. Translation 22 may include a digital servomechanism. The T signal of the translation control consists of a digital pulse flow. The digital servomechanism and the linear motor move the rotatable disk holder 10 at a distance of 1 micron along the radial path 21 for each 232 pulses received by the digital servomechanism 22. The linear motor can use a coil to move the arrow of the linear motor 24 by stimulating the coil with pulses from the translational servomechanism 22. An intefferometer can be used to track the translation of the motor shaft and provide feedback of the linear movement to the translation servomechanism 22. The steering systems! Alternative methods, such as systems using threaded arrows, or arrows coupled with gears, can be understood by a person who knows the technique. The system of Figure 1 operates with a recording medium (not shown) placed on the rotatable disk holder 10. The location system of the recording head 32 guides the linear motor arrow 24, which causes the Rotating disk holder 10 moves linearly. While the rotatable disc holder 10 moves linearly, the recording head 26 follows the first radial path 21 in the rotatable disc holder 10. As the recording head 26 moves relative to the holder of the disc 10, a signal is generated of information 8 by an information processing system 6 and is recorded in the rotatable medium with the rotatable disk holder 10. The information is recorded in the recording medium in a second substantially spiral path (shown in Figure 2). ) defined by the first combined radial path 21 of the optical head 26 and the rotation 11 of the disk holder 10. A constant linear velocity is maintained during recording by controlling the speed of the recording optical head 26 along the the first linear path 21 and controlling the angular velocity of the rotatable disk holder 10 in the rotatable direction (as shown in 11).

In a preferred embodiment illustrated in FIG. 1, the recording optical head 26 is held stationary while the disc holder 10 moves angularly and iineally. A similar spiral path can be obtained if the location system of the disc 10 is held stationary and the recording head 26 moves linearly. Figure 2 is a block diagram of an alternative embodiment using the movement of the recording head 26 on a stationary rotatable disk support 10. Figure 3 illustrates how the geometry of a spiral path can be used to maintain a constant linear velocity . As shown in FIG. 3, the recording head 26 is located on the rotatable disk holder 10. The linear motor arrow 24 is connected to the disk motor 16. While the linear motor arrow 26 moves, the support disk 10 moves along the radial path 21. The disk holder 10 simultaneously rotates around the motor shaft 15. The rotation displacement can be defined by an angular displacement represented in FIG. 3 by the angle q. As the optical head 26 moves radially relative to the disc holder 10, a spiral path 9 is defined in the disc holder 10 while the disc holder 10 rotates. A constant linear velocity is achieved when the velocity represented by the vector Ven Figure 3 is kept constant for all radial positions of the recording optical head 26. The disc locating system 30 updates the angular velocity of the rotatable disc 10 in increments of the angle q, taking into account the initial radius, R0 (defined as the point from which the recording begins) and track density tp (or radial separation between adjacent tracks). By maintaining a cumulative angle q through the process, the linear velocity LV can be maintained constant from R0 towards the outer periphery of the rotatable disk 10. In general, the updated angular velocity represented through ? can be calculated according to the following equation in revolutions per second: 2pLV (Equation)? = 2pR0 + qtp The angular velocity of the rotatable disk holder 26 is indicated by the frequency FR of the rotation control signal R, ie pulses / second. The rotation controller 40 determines the frequency of the rotation control signal R according to the following equation: Krot (t) (Equation 2) FR = 2p where R0I denotes the number of pulses of the rotation control signal R in one revolution of the rotatable disk holder 10. In a preferred embodiment, KR0 (= 525 pulses / revolution.) During the recording process, the disk holder 10 must move to allow the recording head 26 to track the current position in the scroll 9 in conjunction with the rotation of the disk 10. The disk holder 10 can be moved linearly in conjunction with the disk rotation making the signal T of the rotation control a function of the rotation control signal according to the geometry of the system and the specifications of the components. For example, in a preferred embodiment, the frequency FT of the signal T of the translation control can be determined according to the equation: FR X tD X KT (Equation 3) Ft = KR, I heard As indicated above, Krot is 525 pulses / revolution! disc in a preferred embodiment, and Ktrans, the number of pulses per micron of travel of the optical head 26 is 232 pulses / micron. It will be apparent to a person skilled in the art that the relationships described above may vary according to the specifications of the optical recording system. For example, the constants KRot and KTrans depend on the chosen specifications of the modes chosen for the rotation servomechanism 18, the disk motor 16, the translation servomechanism 22, the translation motor 20 and the motor arrow line! 24. The constants K 0Í and Kirans are preferably given in terms of pulses / revolution and pulses / micron, respectively. In addition, variations or alternatives to the relationships described above may be required when the angular velocity of the rotatable disk holder 10 and the translation speed of the optical head 26 (relative to the disk holder 10) are presented in other parameters different from frequency. The preferred embodiment of the rotation controller 40 and the translation controller 60 will be described with reference to FIG. 4. The rotation controller 40 includes rotation determination means consisting of a first pulse counter 44, a second pulse counter 46 and a computer 50. In a preferred embodiment, the rotation determination means determines a cumulative rotation measurement and the computer 50 further determines an angular velocity for the rotatable disk holder 10. The rotation controller 40 includes a fixed oscillator 52, a first frequency synthesizer 54 and a first voltage controlled oscillator (VCO) 57 for generating the R signal of the rotation control. The computer 50 of a preferred embodiment includes a general purpose computer having a memory system, an interrupt input IRQ and an input / output (I / O) system for communication via the data conveyor 51. The conveyor bar The data 51 includes all the signals necessary to direct and provide data transfer to any component connected to the conveyor 51. The first and second pulse counters 44, 46 and the first and second frequency synthesizers 54, 62 are controlled by the computer via data bus 51 as shown in Figure 3. An interrupt service routine (described below) is configured to run when the IRQ interrupt input is activated.

A preferred computer 50 operates with the WINDOWS ™ operating system version 3.1 (or later). The rotation controller 40 is configured to receive a signal Sensor S from the on-line motion sensor 12. The preferred motion sensor 12 in the present invention includes a tachometer that generates a specified sensor signal S as 525 pulses / revolution. An example of a tachometer that can operate as a motion sensor 12 in a preferred embodiment includes an optical encoder having 525 surfaces reflected around the perimeter of a disk. A light source is directed towards the tachometer to reflect the reflected surfaces while the tachometer rotates. The reflections are detected by a photodetector in the optical encoder as pulses of light. A signal transducer converts the pulses of light into a stream of electronic pulses to produce the signal S of the sensor on line 14. The first counter 44 of the rotation controller 40 includes a digital counter, such as a division counter between N , which receives the sensor signal S on line 14 and counts a pre-set number of pulses. The first pulse counter 44 can be initialized to count the preset number of pulses by the computer 50 via the computer data bus 51. By counting the preset number of pulses, the first pulse counter 44 generates a count indicator signal 48.

The account indicator signal 48 activates an interrupt signal at the IRQ interrupt input of the computer 50. In this way, each time the account indicator signal 48 is received in the IRQ of the computer 50, the computer 50 executes the interrupt service routine. The interrupt service routine performs the operations described below with respect to the flow chart of Figure 6.

As described below with reference to Figure 6, the operations that take place in the interrupt service routine result in the calculation of the digital value indicative of a control signal R. of updated rotation. The second pulse counter 46 detects the pulses of the S signals of! online sensor 14 and keeps an account of all pulses received from the start of the recording operation. The second pulse counter 46 can be implemented by a software counter or by a digital pulse counter in the hardware. The software counter includes a variable memory that is updated in the interrupt service routine each time the routine is executed. The program steps in the interrupt service routine add the fixed number of pulses counted by the first pulse counter 44 to the cumulative count which is kept in the variable memory. The implementation of the hardware counter of the second pulse counter 46 may include a digital pulse counter connected to the computer 50 in a manner that would allow the computer 50 to set the counter 46 to zero at the start of the recording operation. The computer 50 can also read the current value of the counter 46 at any time during the recording operation. The count indicated by the second pulse counter 46 at any time represents the cumulative measure of rotation of the rotatable disk holder 10. The advantage of a hardware counter is that the current cumulative measure of rotation is available if it is necessary to perform recovery procedures of error, such as when an interruption is lost. The software counter, on the other hand, can only provide the cumulative measure of rotation from the last interruption received. The computer 50 retrieves the reading of the second pulse counter to obtain the cumulative measure of rotation. Computer 50 uses the cumulative rotation measurement and the relationships in equations 1 and 2 to determine a numerical value of the frequency that is required to establish the angular velocity of the rotatable disk holder 10. The numerical value is converted to a digital frequency signal by a first latched phase loop frequency synthesizer 54. The first frequency synthesizer 54 includes a first reference phase counter 55 receiving a fixed frequency signal 49 from a fixed oscillator 52. The first reference phase counter 55 is previously established by the computer 50 via the data transport bar 51 with a digital value representing a multiple of the angular velocity of the rotatable disk holder 10. The first reference phase counter 55 operates as a division counter between N and counts the pulses received from the fixed frequency signal 49 from the digital value a! that was pre-established The first reference phase counter 55 then generates a signal upon termination of the count. In addition, the interrupt service routine pered by the computer 50 produces a multiplier to a first feedback phase counter 53 on the frequency synthesizer 54. The first feedback phase counter 53 operates in the same manner as the first phase counter of reference 55, except that it counts the pulses of the rotation control signal R on line 58. The value of the multiplier in the first feedback phase counter 53 represents the value that would be multiplied by the value in the first division counter. between N 55 to produce the rotation control signal R selected on line 58. When the first reference phase counter 55 and the first feedback phase counter 53 count down from their preset values, each generates a signal to the phase comparator 56. The phase comparator 56 receives the signals to compare the frequency values represented by the initial numerical values of the first reference phase counter 55 and the first feedback phase counter 53. The phase comparator 56 generates a signal indicative of the error that represents the difference between the two frequency values. The error signal is received by the first VCO 57 to convert it into the rotation control signal R on line 58. The phase comparator 56 indicates that there is no error when the frequency rotation control signal R on line 58 is equal to the frequency determined in the interrupt service routine. A preferred embodiment of a translation controller 60 includes a second frequency synthesizer 62, a second voltage controlled oscillator (VCO) 67 and a frequency divider 68. The second frequency synthesizer 62 includes a second reference phase counter 65, a second feedback phase counter 63 and a second phase comparator 66. The translation counter 60 generates a translation control signal on the line 28. The rotation controller 40 is connected to the translation controller 60 via the line 58. The second reference phase counter 65 of the second frequency synthesizer 62 receives the rotation control signal R as the reference frequency. The second reference phase counter 65 and the second feedback phase counter 63 are initialized to constants that implement Equation 3 for a preferred embodiment. Track density is maintained at a constant value of approximately 1.6 microns. The translation motor 20 is specified to receive 232 pulses to move a micron. According to equation 3, the track density fp is 1.6, raf is 525 pulses / revolution and KíranS is 232 pulses / micron. The frequency Fr of the translation control signal T is, therefore, equal to the frequency Fr of the rotation control signal R multiplied by 1.6, multiplied by 232 and divided by 525.

To implement the relationship of equation 3 with the second frequency synthesizer 62, the second reference phase counter 65 is previously set to 14 and the second feedback phase counter 63 is previously established with the product value of the density of track tp and 99. The output of the second VCO 67, which is also the feedback signal counted by the second feedback phase counter 63, is then divided between the frequency divider 68. By previously setting the frequency divider 68 in 16, the frequency Ft of the translation control signal T follows the relationship in equation 3. The first and second frequency sinietizers 54, 62 of a preferred embodiment each include a latched phase loop chip MC145145 connected to a error integrator. The error incegrador provides a level of voltage that uses the VCO to generate a signal of frequency. Frequency generating systems that are adaptable to the needs of the embodiments of the present invention can be implemented. Figure 5 illustrates a mode in which the frequency synthesis components 52, 54, 57, 67 are replaced by a rotation frequency generator 70. The rotation frequency generator 70 is implemented using function generating units available , like the HP 3325B from Hewlett-Packard. The computer 50 updates the angular velocity of the disk motor 16 in the interrupt service routine, in the same manner as illustrated in FIG. 4. The computer 50 then produces the updated numerical frequency value to the rotation frequency generator 70. by means of the data transport bar 51. The data transport bar 51 can be implemented using an HPIB conveyor bar that operates in accordance with the IEEE standard 488. A translation control signal T on line 28 is generated by a generator translational frequency 80 in the same manner as the rotational control signal R on line 58. The HP 3325B Hewlett-Packard frequency generator described above includes 2 frequency generating channels. One channel generates the signal R of the rotation control on line 58 and the other channel generates the signal. Translational control T on line 28. The interrupt service routine determines the value of the frequency of the translation control signal T in accordance with equation 3 described above. A method for maintaining a constant linear velocity in an optical recording system will be described with reference to the flow chart of Figure 6. The method can be implemented by an apparatus described with reference to Figure 1 using a rotation controller 40 and a translation controller 60 described with reference to FIG. 4. The method illustrated in the flow chart of FIG. 6 uses an interrupt service routine as described above. The interrupt service routine implements a software counter to maintain a cumulative measure of rotation. The routine can be revised to implement a hardware counter by replacing the step of adding the fixed account to the rev counter variable with an instruction to read a port addressed to the hardware counter. The method to maintain a constant linear velocity includes some steps that take place during initialization. The constant linear velocity of the interrupt service routine is set to be invoked at the appropriate interruption level corresponding to the interrupt input IRQ as shown in block 100. The establishment of the interrupt service routine depends on the specific requirements of the operating system and the computer 50 chosen to execute the interrupt service routine. Other steps that take place during system initialization include the initialization of the various counters, such as the first and second pulse counters 44, 46 as shown at 102. The first pulse counter 44 may require constant initialization from the software, or it may be programmed to cycle continuously. The second pulse counter 46 is initialized to zero once, and then by the computer 50 during the operation. Once the system has been initialized, the process starts by locating the optical head in the radial position R0 as shown at 104. The motor of the disk 16 and the translation motor 20 are started as shown in block 106. When reaches the chosen linear speed, the information processor 6 issues the information signal 8 to start the recording process as shown in block 108.

In a preferred embodiment, the disk and translation motors 16, 20 can be controlled using the known motor controller software elements. The recording process typically involves initiating the spiral path in motion and maintenance of the spiral movement! until the disc is recorded. As a consequence, motors 16, 20 are initialized during initialization as part of the process of blocks 104 and 106. After initialization, the constant linear velocity system only updates the speed as described below. Once the recording process is started, the rotation of the rotatable disk holder 10 causes the pulses of the sensor signal S to be counted in the first pulse counter 44 as shown in 1 0. The control system awaits the bill indicator signal 48 which will be activated by the first pulse counter 44. When the first pulse counter 44 activates a count indicator signal 48, the interrupt service routine is invoked as shown in block 112. The execution of the interrupt service routine begins with a block 114 in which the value at which the first counter was initialized is added to the cumulative measure of rotation. The interrupt service routine uses the cumulative measure to calculate a cycle time for the frequency necessary to set the disk motor 16 to an updated angular velocity. The first step in the calculation of the cycle time involves the multiplication of the cumulative measure of rotation, represented by the angle q, by means of the track density tp and then adding the result to 2I7R0 as shown in the bíock 116. The density of tp track in a preferred embodiment is maintained at a constant. A variable track density tp can be implemented by adding a track density input. An example of a track density entry includes a program that calculates a variable track density according to the cumulative rotation measurement. AND! present value of! The cycle time is then divided by the selected linear velocity which has been divided by a scaling factor as shown in block 118. The interrupt service routine then produces the cycle time to the reference counter of the first synthesizer of latched phase loop frequency 54 of FIG. 3. The first scale factor is produced towards the feedback counter of the first frequency synthesizer 54 as shown in block 120. The scale factor ensures that the rotation frequency 58 is the appropriate frequency representing a desired angular velocity. The interrupt service routine described by blocks 114 to 120 calculates the reciprocal of Equation 2 discussed above to calculate the R control signal for rotation. This is because the first frequency synthesizer 54 of phase locked loop compares the cycle time of two frequencies to obtain a phase difference. Once the counters of the first frequency synthesizer 54 are loaded, the rotation control signal R increases or decreases until the phase error between the reference and feedback counters reaches zero. At this point the frequency of the rotation control signal R is at the angular velocity necessary to maintain a constant linear velocity given the cumulative measurement of rotation. The rotation control signal R is received by the translation controller 60 which is shown in block 124. The frequency synthesizer 62 of the translation controller 60 generates the signal T of the translation control as shown in block 126. A mixing in the angular velocity of the rotation disk 10 and the radial velocity of the optical head 26 have been updated, the disk 10 generates pulses to the sensor signal S. The system then waits for an interruption in block 110. Preferred embodiments of the present invention have been described in detail. However, it should be understood that the claims are those that define the invention. One skilled in the art will understand alternative modalities without departing from the scope of the invention. For example, preferred embodiments have been implemented assuming a spiral recording track. The recording track in the recording medium may be formed from approximate concentric circles by a spiral path. The preferred embodiments of the present invention can then be used to provide a constant linear velocity.

In another example, the alternative modes of the rotation controller 40 and the translation controller 60 can be implemented using different parameters to indicate the speed or displacement of either! disc 10 or head 26. In the preferred embodiment described above, the rotation measurement of the viscosity support 10 is indicated by a digital dot flow. In alternative modes, the measurement of the rotation travel may be indicated by a level such as the level of voiíaje or a level of current. In an example of another embodiment, a displacement voltage level indication can be cycled to produce a sawtooth waveform. The clove tooth tip can be used as a count indicator signal and the levels between two peaks as rotation displacement indicators. One skilled in the art can easily understand that a wide variety of circuits can be combined to develop the functions of the rotation determining means. A wide variety of circuits can also be combined to generate a signal indicator of an angular velocity. Examples of such circuits include single throw circuits, circuit integrators and circuits with other waveforms. In a variation of the rotation determining means of a preferred embodiment, the computer 50 updates the digital value of the rotation frequency 58 without using an interruption. Instead, the account indicator signal 48 is an output to a port that the computer 50 detects or polls. The port is polled to determine if the port is at a level that indicates that the first pulse counter 44 has rejected an account. Computer 50 then restarts the port to a level indicating that computer 50 is waiting for a new account. Computer 50 should survey the port frequently enough to ensure that a new account is not activated before the previous account is verified. In another alternative embodiment, the rotation determining means are implemented without a computer 50. A person skilled in the art can easily understand that the instructions developed by the computer 50, in the interrupt service routine, can be achieved by using a combination of digital and analog circuits. The angular velocity can also be generated using combinations of multipliers and digital registers. In addition, the angular velocity can be represented by a signal type different from the frequency to facilitate a computer-less mode. In a variation of the movement sensor 12, the functions of the first and second counters 44, 46 can be integrated into the motion sensor 12. The integration of the components can lead to a digital tachometer reading for the computer 50. In this variation, the data transport bar 51 of the computer 50 is directly connected to the motion sensor 12. The sensor signal S is then detected by a computer program via the data transport bar 51.

Alternative modalities can use alternative methods to generate a chosen frequency. For example, a variable frequency can be generated by a variable oscillator. The frequency varies by adjusting a potentiometer, or a variable capacitor or a variable inductor. It should be appreciated that the foregoing alternatives are presented as examples, and it is not intended to limit the scope of the claims.

Claims (15)

NOVELTY OF THE INVENTION CLAIMS

1. - In an optical recording system consisting of an optical recording head, a rotatable disk holder located near the recording optical head and movable along the first path consisting of a radial component and initiating in a radial position initial, a translation engine to move the rotatable disk holder, a disk motor coupled to the disk holder to rotate the disk holder at an eligible angular velocity, a motion sensor coupled to the disk holder and operative to generate a sign! of sensor indicative of the rotation of! disk holder, an operational translation controller to move the disk holder along the first path, the improvement consists of: a controller of response rotation to the sensor signal and operative to determine a cumulative measure of rotation and set the angular velocity of the disk motor as a function of the cumulative rotation measurement to maintain a linear speed chosen between the register head and the rotation disk.

2. The optical recording system according to claim 1: further characterized in that the sensor signal consists of a plurality of pulses; further characterized in that a cumulative number of the plurality of pulses is indicative of a rotation displacement of the disk holder; and further characterized in that the rotation controller consists of a first counter of pulses of response to the pulses.

3. The optical recording system according to claim 2, further characterized in that the rotation controller further comprises: a density input to receive a chosen track density; means for generating an account indicator signal upon receipt of a fixed number of the plurality of pulses; and rotation determining means are determined to determine the cumulative measure of rotation in response to the count indicator signal, the cumulative measure of rotation determined as a function of track density.

4. The optical recording system according to claim 1, further characterized in that e! The rotation control consists of a phase locked loop frequency synthesizer to generate a rotation control signal indicative of the angular velocity of the disk motor, the rotation control signal determined in accordance with the cumulative rotation measurement and the speed linear chosen.

5. The optical recording system according to claim 1, further characterized in that the rotation controller consists of a frequency generator to generate a rotation control signal indicative of the angular speed of the disk motor, the control signal of rotation determined in accordance with the cumulative measure of rotation and the linear speed chosen.

6. - In an optical recording system consisting of a rotatable disk holder, an optical recording head placed close to the rotatable disk holder, and movable along the first path consisting of a radiating component! and start in a radiant position! initial, a translation motor to move the optical recording head, a disk motor coupled to the disk holder to rotate the disk holder at an eligible angular velocity, a motion sensor coupled to the disk holder and operative to generate a sensor signal indicative of rotation of the disk holder, the improvement consists of: an operating translation controller for moving the recording head along the first path; and a rotational controller responsive to the sensor and operative signal to determine a cumulative rotational measure and to establish the angular velocity of the disk motor as a function of the cumulative rotational measure to maintain a linear velocity chosen from the head of recording and the rotation disc.

7. The optical recording system according to claim 6: further characterized by the signal! sensor consists of a plurality of pulses; further characterized in that a cumulative number of the plurality of pulses is indicative of a rotational displacement of the disc holder and further characterized in that the rotation controller comprises a first pulsed response counter.

8. The optical recording system according to claim 7, further characterized in that the rotation controller further comprises: a density input to receive a chosen track density; means for generating an account indicator signal upon receipt of a fixed number of the plurality of pulses and means for determining rotation to determine the cumulative measure of rotation in response to the account indicator signal, the cumulative measure of rotation determined as a function of the track density chosen.

9. The optical recording system according to claim 6, further characterized in that the rotation controller consists of a phase loop frequency synthesizer engaged to generate a rotation control signal indicative of the angular velocity of the disk motor , the rotation control signal determined in accordance with the cumulative rotation measurement and the linear speed chosen.

10. The optical recording system according to claim 6, further characterized in that the rotation controller comprises a frequency generator for generating a rotation control signal indicative of the angular velocity of the disk motor, the control signal of rotation determined in accordance with the cumulative measure of rotation and the linear speed chosen.

11. In an optical recording system, a method for maintaining a radially movable and rotabie disk at a constant linear velocity relative to an optical recording head, the method consists of the steps: generating a translation of the relative recording optical head to the rotatable disk holder, the translation starts from an initial radial position along a radial path; rotating the rotatable disk at an initial angular velocity; determine a cumulative measure of rotation of the rotation disk and update the angular velocity of the rotation disk in response to the cumulative measure of rotation to maintain the constant linear velocity.

12. The method according to claim 11, further characterized in that the step for determining the cumulative measure of rotation consists of the steps of: generating pulses in response to the rotation of the rotatable disk; count the pulses and maintain a count of puises and also characterized because the step to determine the cumulative measure of rotation is given in response to the pulse count.

13. The method according to claim 11, further characterized in that the step for determining the cumulative measure of rotation further comprises the step of: generating an account indicator signal each time a fixed pulse number is counted; and determining a cumulative measure of turnover by recovering a cumulative pulse count each time an account indicator signal is generated.

14. The method according to claim 11, further characterized in that the step of generating a translation further comprises the step of: moving a rotatable disk holder in a linear direction relative to the stationary recording optical head.

15. - The method according to claim 11, further characterized by the step of moving the recording optical head in a linear direction relative to the rotatable disk holder.