Tracking control in image recorders and/or reproducers

Abstract: In a tracking control method and apparatus for an image recorder and/or reproducer, there are provided a method and device which can accomplish high-performance tracking control by using a variable capstan speed instruction which is reflected by a degree of tracking error instead of using a conventional capstan speed instruction wherein the tracking error is not reflected. For this, a tracking control method includes the steps of determining a degree of tracking control by performing a predetermined gain control on the tracking error, and generating the variable capstan speed instruction wherein the degree of tracking control is reflected (S102), and determining the degree of speed error of the capstan motor (36) by comparing the capstan speed instruction with the actual rotation speed of capstan motor (36) (S106), and determining a degree of speed control of the capstan motor wherein the tracking error is reflected by performing a predetermined gain control on the speed error (S108). Thus, there are enabled rapid control wherein tracking compatibility during the control is improved, easy coefficient control and a single system.

Description: The present invention relates to tracking control in image recorders and/or reproducers. An image recorder and/or reproducer such as a video cassette recorder (VCR) or video camera (camcorder) creates a poor display by generating beats on a screen when tracking is not well-controlled. Therefore, good tracking control is essential to obtain a good display. In a tracking control operation, a head is controlled correctly so as to scan a predetermined track, to thereby get a maximum envelope output during reproduction. A separate control signal is used for tracking control. In a VHS-VCR, tracking is performed by using a control signal which is recorded on a control track of a tape by a fixed head. Further, in an 8mm VCR system, a pilot signal called an automatic track finding (ATF) signal having four kinds of different frequencies is recorded on a track of the tape, and then is used for reproduction in such a way that the tracking error, i.e. the degree of deviation from the track which the current head is scanning, is detected and reduced. At this time, the detected tracking error can be minimized by controlling the spinning speed of the respective capstan motor. That is, the object of the tracking control is control of the spinning speed of capstan motor. There now follows an example of a conventional tracking control method with reference to Figures 1 to 4 of the accompanying diagrammatic drawings, in which: Figure 1A and Figure 1B show the relation of scanning traces of a head and tracking error of a VCR; Figure 2 is a block diagram showing a capstan servo system for a conventional tracking control; Figure 3 illustrates an example wherein the capstan servo system shown in Figure 2 is applied to a VHS-VCR; and Figure 4 comparatively illustrates trackings in a normal track and in a modified track. Figure 1A and Figure 1B show the relation between the scanning traces of the head and tracking error of a conventional VCR, wherein, for convenience, the generation of a positive error indicates that the head locates prior to the track to be scanned while the generation of a negative error indicates that the head locates after the track is scanned. Following is the basic principle of tracking control. Referring to Figure 1, when the head is prior to the predetermined track, that is, when the head is located in a P1-level track, the tape proceeds slowly by slowing down the speed of the capstan motor. When the head is behind the predetermined track, that is, when the head is located in a P2-level track, the tape proceeds faster by increasing the speed of the capstan motor. Therefore, the head is controlled so as to scan the predetermined track correctly. The basic principle of tracking control is still appropriate for embodiments of the present invention as well as for conventional methods. A conventional structure of capstan servo for tracking control is as shown in Figure 2. Referring to Figure 2, a speed control signal for a capstan motor 20 is applied to a capstan motor driver 18 and is calculated from an amount of capstan speed control detected from a tracking controller 12 and an amount of tracking control detected from a capstan controller 14, respectively, the above two amounts being added by an adder 16. Figure 3 shows an embodiment wherein the capstan servo system shown in Figure 2 is applied to a VHS-VCR. Here, an amount of capstan speed control is calculated under the assumption that there is a predetermined normal track, and a capstan speed instruction (f), which corresponds to a regular spinning speed of the capstan motor which is needed when a head runs correctly in the above normal track, is a reference value. The reference value and the actual speed of the capstan motor 27 actually measured from a frequency generator 29 when capstan motor 27 spins, are compared in a capstan speed error detector 21. Then, the degree of error calculated from this comparison is changed into a degree of speed control of capstan motor 27 in a capstan speed controller 22, which is not related to the degree of tracking control for compensating the tracking error. A record pulse which is synchronized with a track start point (hereinafter, termed a "control pulse") is recorded on a control track. Also, a degree of capstan tracking error is output from a capstan phase comparator 23 by means of phase comparison between the control pulse which is reproduced by a fixed head 28 (called a "control head") and a head switching pulse of which a pre-arranged frequency is provided. Then, the degree of capstan tracking error is multiplied by a predetermined gain coefficient or is differentiated or integrated so as to be output as a degree of capstan tracking control, i.e. a predetermined physical amount, in a capstan phase controller 24, thereby performing phase control of the capstan motor 27 in order to control tracking. The degree of capstan speed control of capstan speed controller 22 and the degree of tracking control of capstan phase controller 24 are added in an adder 25, and the result is fed to a capstan motor driver 26 which drives the capstan motor 27. However, the above-mentioned conventional method generates various kinds of problems when the direction for controlling the speed of capstan motor and the direction for controlling the tracking are different. The following is an explanation with reference to Figure 2 and Figure 4. Figure 4 shows the tracking when the head runs in a track which differs greatly from the normal track. As can be seen in Figure 4, the trace of the head which capstan speed controller 14 aims to control is the predetermined normal track (the A direction of Figure 4), while the trace of the head which tracking controller 12 aims to control is the modified track(the B direction of Figure 4). Accordingly, when the direction for controlling the speed of capstan motor 20 and the direction for controlling the tracking are different, correct tracking is difficult since the speed controller prevents capstan motor 20 from moving in the direction of reducing the tracking error. Such a conventional device is disclosed in JP-A-2 098 856 which reflects the preamble of the appended independent claims. A precise gain control for the degree of control for the above two directions is needed to solve the problem. Therefore, the gains of tracking controller 12 and capstan speed controller 14 should be controlled precisely. However, the design of a device which is additionally required for the gain control as well as the gain control itself is difficult. Even though the device has a gain control function, there still is a problem of compatibility between the two devices if the recording device and the reproduction device are different. Partial deterioration of tracking may cause little problem in a VHS-VCR or in an 8mm VCR, since the track width is quite large (58µm for VHS, and 21µm for 8mm). However, there is a problem of lowering performance in the case of a digital VCR which requires a high density recording, because very high performance tracking is needed if the track width is below 10µm. Preferred embodiments of the present invention aim to provide a method and device which can control tracking by using a variable capstan speed instruction wherein a degree of tracking control calculated from a tracking error is reflected, instead of using a conventional capstan speed instruction wherein the tracking error is not reflected as a reference value which is used for calculating the degree of capstan motor speed control. According to one aspect of the present invention, there is provided a tracking control method for an image recorder and/or reproducer, characterised by the steps of: calculating a degree of tracking control, by performing a predetermined gain control on said tracking error, and converting it into said degree of tracking control; generating a variable capstan speed instruction in which said degree of tracking control is reflected; determining a speed error, by comparing said capstan speed instruction and an actual rotation speed of the capstan motor, thereby to determine a degree of speed error of the capstan motor; and calculating a degree of speed control, by performing a predetermined gain control on said speed error, and calculating therefrom said degree of speed control of the capstan motor in which said tracking error is reflected. Preferably, said variable capstan speed instruction of said speed instruction generation step is obtained by adding said degree of tracking control to a capstan speed instruction that is required when tracking error is not considered. A head switching pulse having a predetermined frequency may be used as a reference signal, and said tracking error expressed by a phase difference resulting from a comparison between the phases of said reference signal and of a control pulse on a recording medium. Said tracking error may be expressed by a frequency difference of a pilot signal which has four different frequencies. According to another aspect of the present invention, there is provided a tracking control apparatus for generating a degree of capstan speed control for a capstan motor controlling the running of a recording medium, said apparatus characterised by : a tracking controller which outputs a variable capstan speed instruction from a degree of tracking control calculated by performing a predetermined gain control on a tracking error; and a capstan speed controller which performs a predetermined gain control on a speed error of the capstan motor calculated by comparing an actual capstan speed with a reference value derived from said capstan speed instruction, and outputs said degree of capstan speed control. Said tracking controller and capstan speed controller may be included in a micro-computer which controls functions of said image recorder and/or reproducer. Said tracking controller may comprise: a tracking controller which performs a predetermined calculation on said tracking error for a gain control operation and outputs said degree of tracking control; and a capstan speed instruction generator which outputs said variable capstan speed instruction that corresponds to said degree of tracking control. Said calculation by said tracking controller may comprise a proportional-integration-differentiation (PID) control. Preferably, said capstan speed instruction generator is a voltage control oscillator which outputs a variable frequency signal that corresponds to said degree of tracking control. Preferably, said capstan speed controller comprises: a capstan speed error detector which compares said capstan speed instruction with the actual speed of the capstan motor, and then detects said capstan speed error; and a capstan speed controller which performs a predetermined calculation on said capstan speed error for gain control, and then outputs said degree of capstan speed control. Preferably, said calculation by said capstan speed controller comprises a proportional-integration-differentiation (PID) control. Preferably, the tracking control apparatus comprises: a capstan motor which controls the running of a recording medium; a capstan phase comparator which compares the phases of a head switching pulse of a pre-set frequency and a control pulse, and then outputs a degree of tracking error expressed by the phase difference; a capstan phase controller which performs a predetermined calculation for gain control on said tracking error resulting from said capstan phase comparator, and then outputs a degree of tracking control; a capstan speed instruction generator which generates a variable capstan speed instruction related to said degree of tracking control; a capstan speed error detector which compares said capstan speed instruction and an actual capstan speed, and then generates a speed error of said capstan motor; a capstan speed controller which performs a predetermined calculation on the speed error of said capstan motor for gain control, and then outputs a capstan speed control signal; and a capstan motor driver which drives said capstan motor according to the output of said capstan speed controller. Preferably, said calculation by said capstan phase controller comprises a proportional-integration-differentiation (PID) control. Preferably, said capstan speed instruction generator comprises a voltage-controlled oscillator which outputs a variable frequency signal corresponding to said degree of tracking control. Preferably, said calculation by said capstan speed controller comprises a proportional-integration-differentiation (PID) control. According to a preferred embodiment of the present invention, there is provided a tracking control apparatus for an 8mm image processing apparatus which comprises a capstan motor that controls the running of a recording medium and a capstan driver, said apparatus comprising: a detector which detects a pilot signal for discriminating tracks; an auto track finding (ATF) controller which outputs an ATF signal according to a frequency difference of said detected pilot signal, to represent a degree of tracking error; and a micro-computer which generates a variable capstan speed instruction from a degree of tracking control obtained by performing a predetermined gain control calculation on said tracking error, performs a predetermined gain control on a capstan motor's speed error obtained by comparing an actual capstan speed with a capstan speed instruction which serves as a reference value, and then outputs a capstan speed control signal to said capstan motor driver. Preferred embodiments of the present invention may be based on a basic principle of tracking control as in a conventional method. As compared with the conventional method wherein the degree of capstan speed control is separately calculated from the degree of tracking control, the degree of capstan speed control is preferred embodiments of the present invention has a dependant relationship with the degree of tracking error (or the degree of tracking control) since the degree of capstan speed control is reflected by the degree of tracking error (or the amount of tracking control). For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example, to Figures 5 to 8 of the accompanying diagrammatic drawings, in which: Figure 5 is a block diagram showing the structure of one example of a tracking control apparatus of a VCR according to the present invention; Figure 6 is a block diagram showing in more detail one example of an embodiment of a tracking control apparatus of a VCR according to the present invention; Figure 7 is a block diagram showing another embodiment of a tracking control apparatus of a VCR according to the present invention; and Figure 8 is a flowchart showing one example of a procedure of a tracking control method of a VCR according to the present invention. First, a process of calculating a degree of tracking control will be explained. The process of calculating the degree of tracking control is one in which the tracking error is multiplied by a predetermined gain or is differentiated or integrated, thereby determining the degree of tracking control. That is, a proportional-integration-differentiation (PID) control is accomplished. Here, the physical dimension expressing the degree of tracking error is variable. That is, the physical dimension varies depending on the characteristic of a calculating apparatus which calculates the degree of tracking control from the degree of tracking error. For example, the tracking error may be represented by a phase difference when the tracking error is calculated by comparing a reference signal with the phases of control pulses on tape which is read via a head, assuming that head switching pulses of predetermined frequency are provided as the reference signal. When a pilot signal in which four different frequencies are provided is used, frequency difference may represent the tracking error. The following is a process of generating speed instruction. This process is for obtaining a capstan speed instruction, i.e. a reference value which is needed for calculating a speed error of a capstan motor, and particularly, for obtaining a capstan speed instruction in which the degree of tracking control is reflected. The method for obtaining the capstan speed instruction wherein the degree of tracking control is reflected can be variable. One possible method is to add to the degree of tracking control, obtained from a gain control performed on the tracking error, the capstan speed instruction needed when the tracking error is not considered, and the result is then used as a capstan speed instruction in the process of generating a speed instruction. Here, the degree of tracking error is not a constant value, and the capstan speed instruction is a variable value. Also, the process of calculating the amount of tracking control should be prior to the process of generating the speed instruction wherein the capstan speed instruction is generated. Referring now to Figure 5, which is a block diagram of tracking control device of a VCR according to one example of the present invention, reference numerals 30, 32, 34 and 36 denote a tracking controller, a capstan motor speed controller, a capstan motor driver and a capstan motor, respectively. Here, tracking controller 30 is directly used for the processes of calculating the degree of tracking control and generating a speed instruction. Referring to Figure 5, the capstan speed instruction obtained from tracking controller 30 is used as a comparative reference value in estimating the speed error of the capstan motor, as described above, like the capstan speed instruction obtained from the conventional tracking controller 12 of Figure 2. However, the process of estimating the capstan speed instruction is different from the conventional method in that, in Figure 5, there is a close relation with the degree of tracking error. That is, the capstan speed instruction of Figure 5 is obtained under the assumption that the degree of tracking control is calculated. Meanwhile, the capstan speed instruction obtained from tracking controller 30 is a variable value which includes the degree of tracking control according to the tracking error and varies as follows. That is, when the head is prior to the track that is to be scanned (e.g. when the head is located in a P1-level track in Figure 1), that is, when the tape speed has to be reduced, the value of capstan speed instruction obtained from the above process of generating a speed instruction changes to the direction wherein the speed of the capstan motor is decreased. On the contrary, when the head is behind the track that is to be scanned (e.g. when the head is located in P2-level track in Figure 1), that is, when the tape should run faster, the capstan speed instruction value changes to the direction wherein the capstan motor speed is increased. Here, the physical dimension expressing the amount of tracking control and the capstan control instruction is variable. That is, the two physical amounts can be expressed in various forms depending on the apparatus carrying out the process. For example, the spinning (rotation) speed of capstan motor is generally expressed as a pulse frequency output from a frequency generator (FG). Therefore, it is convenient that the degree of the capstan speed instruction is to be related to the pulse frequency. The following is a description of a process of determining speed error. The degree of speed error of the capstan motor which is obtained in the process of determining the speed error is calculated by comparing the capstan speed instruction and the actual spinning speed of the capstan motor. That is, the difference between the reference value and the size of the actual spinning speed is the very amount of speed error of the capstan motor, assuming that the capstan speed instruction is a reference value. Accordingly, the degree of speed error calculated in the process for determining the speed error is the degree of error caused by reasons other than the tracking error, and a conventional process which adds the degree of speed error to the degree of tracking control is unnecessary. The following is a description of a process of calculating a degree of speed control. The process of calculating the degree of speed control is for calculating the degree of speed control of the capstan motor needed for reflecting the degree of error obtained from the previous process, i.e. the process of determining the speed error, from the spinning speed of capstan motor most stably, promptly and correctly. The degree of speed control is utilized as a driving signal of the capstan motor by the driving means of the capstan motor. Capstan speed controller 32 of Figure 5 is the means for determining the speed error and calculating the degree of speed control. Figure 6 is a block diagram showing an embodiment of apparatus used for performing a method of the present invention, as applied to a VHS-VCR. Referring to Figure 6, reference numeral 41 denotes a capstan phase comparator, 42 denotes a capstan phase controller, 43 denotes a capstan speed instruction generator, 44 denotes a capstan speed error detector, 45 denotes a capstan speed controller, 46 denotes a capstan motor driver, 47 denotes a capstan motor, 48 denotes a fixed head, and 49 denotes a frequency oscillator. Capstan phase comparator 41 compares the phases of a head switching pulse of a predetermined frequency and of a control pulse which is reproduced by fixed head 48, and then calculates the tracking error. Capstan phase controller 42 multiplies the tracking error by a predetermined gain coefficient or performs a differentiation or integration on the tracking error, which then is output as a value corresponding to a degree of tracking control. Capstan speed instruction generator 43 outputs a variable capstan speed instruction which is related to the frequency of the pulse representing the degree of tracking control. Here, capstan phase controller 42 and capstan speed instruction generator 43 correspond to tracking controller 30 of Figure 5. When the degree of tracking control output from capstan phase controller 42 is a voltage signal whose magnitude corresponds to the tracking error, capstan speed instruction generator 43 can be constructed using a voltage-controlled oscillator (VCO) which outputs a frequency signal that corresponds to the degree of tracking control, i.e. a voltage. Meanwhile, capstan speed error detector 44 compares the capstan speed actually measured from frequency oscillator 49 and the capstan speed instruction, i.e, a reference value, provided by capstan speed instruction generator 43, and then calculates the speed error of the capstan motor. Capstan speed controller 45 multiplies the speed error of the capstan motor by a regular gain coefficient or performs a predetermined gain control, for example, a differentiation or an integration, on the speed error of capstan motor, and outputs a capstan speed control signal. Here, capstan speed error detector 44 and capstan speed controller 45 correspond to the capstan speed controller 32 of Figure 5. Tracking controller 30 and capstan speed controller 32 may use hardware for performing their functions; they also may use a micro-computer provided with software which can perform the functions of the hardware. Figure 7 is a block diagram showing another embodiment of tracking control apparatus according to the present invention, that is, an embodiment applying to an 8mm VCR. Referring to Figure 7, reference numeral 51 denotes a reproduction head, 52 denotes a reproduction amplifier, 53 denotes a signal processing part, 54 denotes an ATF controller, 55 denotes an A/D converter, 56 denotes a micro-computer, 57 denotes a D/A converter, 58 denotes a capstan motor driver, 59 denotes a capstan motor, and 60 denotes a frequency oscillator. Reproduction amplifier 52 picks up a signal recorded on a tape from reproduction head 51 and then amplifies the picked-up signal. The frequency bands of the signals recorded on 8mm video tape can be described as follows. Four kinds of pilot signals (f1-f4) are recorded in a 100KHz to 160KHz band, an FM audio (AFM) signal is recorded in a 1.4MHz to 1.6MHz band, and a colour signal which is AM-modulated onto a centre frequency of 743KHz, and a luminance signal of 4.2MHz to 5.4MHz are also recorded. Signal processor 53 detects an image signal, audio signal and a pilot signal for discriminating the tracks which are recorded so as to have a specific band as described above, and then processes the signals. ATF controller 54 detects the degree of ATF error among the signals output from signal processor 53 using the pilot signals, and converts the degree of ATF error in A/D converter 55 into the form of a digital signal, and then outputs the converted signal to micro-computer 56. Among the specific frequencies of the four pilot signals, f1 is 102.544KHz, f2 is 118.951KHz, f3 is 165.21KHz and f4 is 148.689KHz. The difference of the pilot output level is checked and used as a tracking error signal. That is, the following expression obtain the tracking error signal, and the degree of deviation of the head from the track can be discriminated, depending on the spectral components. f1 - f2 ≒ f3 - f4 ≒ Δ fA ≒ fH f1 - f4 ≒ f2 - f3 ≒ Δ fB ≒ 3fH Micro-computer 56 performs a predetermined gain control on the amount of ATF error (tracking error) thereby calculating the degree of tracking control Δf. Micro-computer 56 then adds or subtracts this degree of tracking control to or from the capstan speed instruction, i.e. a fixed capstan instruction value f, wherein the tracking is not considered, thereby providing a speed instruction f±Δf for the capstan motor 59. As a result, the variable capstan speed instruction f±Δf is formed, which then is converted into an analog signal in D/A converter 57. Then, capstan motor driver 58 controls the actual speed of capstan motor 59 so as to accord with the speed instruction. The capstan motor of an 8mm VCR is controlled to be rotated at a regular speed. Therefore, the degree of tracking control is added to the degree of speed control, thereby driving the capstan motor entirely. Figure 8 is a flowchart showing the procedure of one example of a method of the present invention, wherein the process for calculating the degree of speed control of capstan motor required when micro-computer 56 is used for tracking control is illustrated. After step S100 wherein the tracking error is read from the micro-computer, the necessary degree of tracking control is determined by performing a proportional-integration-differentiation control algorithm, on the above tracking error. Then, step S102 adds the degree of tracking control to the capstan speed instruction required for rotating the capstan motor at the speed required when there is no tracking error, and generates a new capstan speed instruction. Then, the actual rotation speed of capstan motor is input in step S104, and the degree of speed error is obtained in step S106 by calculating the difference between the actual rotation speed and the capstan speed instruction generated from step S102 (for example, the difference of pulse clock frequency). Then, the capstan speed control signal is obtained in step S108 by performing a proportional-integration-differentiation (PID) control algorithm process on the above degree of speed error. Then, the capstan speed control signal is output to capstan motor driver in step S110. Steps S100 to S110 repeat as a process cycle. The above-described embodiments of the present invention have good compatibility of tracking even when the devices for recording and reproducing are different. Also, when the track is largely curved, that is, when the track linearity is poor, correct tracking is possible. Additionally, coefficient control and design for the system are made easy since the control signal is processed in one direction.

Claims: A tracking control method for an image recorder and/or reproducer, said method comprising the steps of: determining (41) a tracking error; determining (44) a speed error; and calculating a degree of speed control of a capstan motor using said tracking error and said speed error; characterised by the steps of: calculating (42) a degree of tracking control, by performing a predetermined gain control on said tracking error, and converting it into said degree of tracking control; generating (43) a variable capstan speed instruction in which said degree of tracking control is reflected; in said step of determining (44) a speed error, comparing said capstan speed instruction and an actual rotation speed (FG) of the capstan motor (47), thereby to determine a degree of speed error of the capstan motor; and calculating (45) a degree of speed control, by performing a predetermined gain control on said speed error, and calculating therefrom said degree of speed control of the capstan motor (47) in which said tracking error is reflected. A tracking control method according to claim 1, wherein said variable capstan speed instruction of said speed instruction generation (43) step is obtained by adding said degree of tracking control to a capstan speed instruction that is required when tracking error is not considered. A tracking control method according to claim 1 or 2, wherein a head switching pulse having a predetermined frequency is used as a reference signal, and said tracking error is expressed by a phase difference resulting from a comparison (41) between the phases of said reference signal and of a control pulse on a recording medium. A tracking control method according to claim 1 or 2, wherein said tracking error is expressed by a frequency difference of a pilot signal which has four different frequencies. A tracking control apparatus for generating a degree of capstan speed control for a capstan motor (47) controlling the running of a recording medium, said apparatus characterised by : a tracking controller (30) which outputs a variable capstan speed instruction from a degree of tracking control calculated by performing a predetermined gain control on a tracking error; and a capstan speed controller (32) which performs a predetermined gain control on a speed error of the capstan motor calculated by comparing an actual capstan speed with a reference value derived from said capstan speed instruction, and outputs said degree of capstan speed control. A tracking control apparatus according to claim 5, wherein said tracking controller (30) and capstan speed controller (32) are included in a micro-computer (56) which controls functions of said image recorder and/or reproducer. A tracking control apparatus according to claim 5, wherein said tracking controller (30) comprises: a tracking controller (42) which performs a predetermined calculation on said tracking error for a gain control operation and outputs said degree of tracking control; and a capstan speed instruction generator (43) which outputs said variable capstan speed instruction that corresponds to said degree of tracking control. A tracking control apparatus according to claim 7, wherein said calculation by said tracking controller (42) comprises a proportional-integration-differentiation (PID) control. A tracking control apparatus according to claim 7 or 8, wherein said capstan speed instruction generator (43) is a voltage control oscillator which outputs a variable frequency signal that corresponds to said degree of tracking control. A tracking control apparatus according to any of claims 5 to 9, wherein said capstan speed controller (32) comprises: a capstan speed error detector (44) which compares said capstan speed instruction with the actual speed of the capstan motor, and then detects said capstan speed error; and a capstan speed controller (45) which performs a predetermined calculation on said capstan speed error for gain control, and then outputs said degree of capstan speed control. A tracking control apparatus according to claim 10, wherein said calculation by said capstan speed controller (45) comprises a proportional-integration-differentiation (PID) control. A tracking control apparatus as claimed in claim 5, comprising: a capstan motor (47) which controls the running of the recording medium; a capstan phase comparator (41) which compares the phases of a head switching pulse of a pre-set frequency and a control pulse, and then outputs a degree of tracking error expressed by the phase difference; a capstan phase controller (42) which performs a predetermined calculation for gain control on said tracking error resulting from said capstan phase comparator, and then outputs a degree of tracking control; a capstan speed instruction generator (43) which generates a variable capstan speed instruction related to said degree of tracking control, said capstan phase controller (42) and said capstan speed instruction generator (43) together forming said tracking controller (30); a capstan speed error detector (44) which compares said capstan speed instruction and an actual capstan speed, and then generates a speed error of said capstan motor; a capstan speed controller (45) which performs a predetermined calculation on the speed error of said capstan motor for gain control, and then outputs a capstan speed control signal, said capstan speed error detector (44) and said capstan speed controller (45) together forming said capstan speed controller (32); and a capstan motor driver (46) which drives said capstan motor (47) according to the output of said capstan speed controller (45). A tracking control apparatus according to claim 12, wherein said calculation by said capstan phase controller (42) and/or said capstan speed controller (45) comprises a proportional-integration-differentiation (PID) control. A tracking control apparatus according to claim 12 or 13, wherein said capstan speed instruction generator (43) comprises a voltage-controlled oscillator which outputs a variable frequency signal corresponding to said degree of tracking control. A tracking control apparatus according to any of claim 5 to 14 used in an image recorder and/or reproducer. A tracking control apparatus as claimed in claim 5, for an 8mm image processing apparatus which comprises a capstan motor (59) that controls the running of a recording medium and a capstan driver (58), said apparatus comprising: a detector (53) which detects a pilot signal for discriminating tracks; an auto track finding (ATF) controller (54) which outputs an ATF signal according to a frequency difference of said detected pilot signal, to represent a degree of tracking error; and said tracking controller (30) and said capstan speed controller (32) together being a micro-computer (56) which generates said variable capstan speed instruction from said degree of tracking control obtained by performing a predetermined gain control calculation on said tracking error, performs a predetermined gain control on said capstan motor speed error obtained by comparing an actual capstan speed with said capstan speed instruction which serves as a reference value, and then outputs a capstan speed control signal to said capstan motor driver (58).

Inventors: KIM JUNG-TAE, KIM, JUNG-TAE
Applicants: SAMSUNG ELECTRONICS CO LTD, SAMSUNG ELECTRONICS CO., LTD.
Application year: 1993
Main classification: G11B15
IPC codes: G11B5, G11B15