Abstract:
An automatic tracking method for detecting an optimized, accurate tracking level in a video tape recorder system to automatically sustain picture quality monitors a variation of the tracking level to continually detect a highest tracking level. Tracking data corresponding to the highest tracking level is set as output tracking data, to continually sustain optimized tracking.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to an automatic tracking control method in a video tape recorder and particularly although not exclusively to a method for continually sustaining an optimized tracking level by monitoring the tracking levels. 
     In FIG. 1, a block diagram of a general tracking control device in a video tape recorder system is schematically illustrated, wherein a program contained in a system controller 6 generates tracking data TRDT to a servo 7 and then, the servo 7 provides a deck 1 with a capstan control signal CAP-CTL in accordance with the tracking data TRDT, to control a rotational speed of a capstan. Then, a head in the deck 1 picks up an instataneous tracking level indicative of a current tracking state according to the rotational speed of the capstan and provides the instantaneous tracking level to the system controller 6, to sustain an optimized tracking level by comparing instantaneous tracking levels. 
     FIGS. 2A to 2D, disclose a conventional automatic tracking method performed by the videotape recorder system of FIG. 1 as in Korean Patent application No. 89-19419. According to the conventional method, the system controller 6 having an analog-to-digital converter therein executes the automatic tracking as shown in FIGS. 2A to 2D. However, when such an automatic tracking method is employed, in some occasions the system controller 6 may misrecognize variation valves of the instantaneous tracking levels picked up by the head and/or may result in a mal-operation because the automatic tracking operation depends simply on a comparison of the instantaneous tracking levels by means of the system controller 6. Therefore, occasionally, a noisy video signal may be misrecognized for a nose-free video signal particularly when a worn-out video tape is used, and thus the optomized tracking level may be miscalculated, thereby resulting in deteriorated automatic tracking. 
     SUMMARY OF THE INVENTION 
     It is accordingly an object of the present invention to provide a method for detecting an optimized, accurate tracking level in a videotape recorder system to automatically sustain picture quality. 
     It is another object of the present invention to provide an automatic tracking method for continually sustaining a good picture quality in a videotape recorder system, regardless of the condition of a video tape quality. 
     According to one aspect of the present invention, an automation tracking method comprises the steps of: generating a plurality of first tracking data sets each having corresponding digital tracking level values to be stored in a memory, and determining whether the digital tracking levels are steadily increasing, to monitor variation of the digital tracking level values; if the digital tracking levels are steadily increasing, increasing repeatedly the tracking data by predetermined steps each having corresponding digital tracking levels to be stored in the memory, and comparing a current tracking level value with a preceding tracking level value, to set the tracking data corresponding to the preceding tracking level value for output tracking data if the current digital tracking level value is lower than the preceding tracking level value; if the digital tracking levels are not steadily increasing in the first tracking data generation step, generating a plurality of second tracking data sets each having corresponding digital tracking levels to be stored in a memory, and determining whether the digital tracking level values are steadily increasing, to monitor variation of the digital tracking level values; if the digital tracking levels are steadily increasing in the second tracking data generation step, decreasing repeatedly the tracking data by the predetermined steps each having corresponding digital tracking levels to be stored in the memory, and comparing the current tracking level value with the preceding tracking level value, to set the tracking data corresponding to the preceding tracking level value for the output tracking data if the current digital tracking level value is lower than the preceding tracking level value; and if the digital tracking levels are not steadily increasing in the second tracking data generation step, comparing entire tracking level values stored in the memory in the preceding steps to detect a highest tracking level value and corresponding tracking data, the detected tracking data being set as output tracking data. 
    
    
     BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS 
     For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made by way of example to the accompanying diagrammatic drawings, in which: 
     FIG. 1 shows a block diagram of a general tracking control device in a videotape recorder system to which the present invention is applied; 
     FIGS. 2A to 2D show flow charts of a conventional automatic tracking method; 
     FIGS. 3A to 3D show flow charts of an automatic tracking method according to the present invention; and 
     FIG. 4 shows tracking level curves with respect to the tracking data according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference to FIGS. 3A to 3D, in steps 301 through 306, n (present tracking data), (n+4), (n+8), (n+12, and (n+16) tracking data are sequentially generated by the system controller 6. For each tracking data, tracking level values S 1 , S 2 , S 3 , S 4 , and S 5  (See FIG. 4) are consequently stored in a memory after the lapse of 0.1 second, each time. Then, whether the tracking level values are in the order of S 1  &lt;S 2  &lt;S 3  &lt;S 4  &lt;S 5  is checked, to detect a variation of the tracking levels. 
     If the tracking levels are increasing such as S 1  &lt;S 2  &lt;S 3  &lt;S 4  &lt;S 5 , the tracking data are also increased by the system controller 6 by (n+4k), where k=5, 6, 7, . . . , 20, and then a current tracking level is detected and compared with a preceding tracking level; as a result, if the current tracking level is lower than the preceding tracking level, then the preceding tracking data is set as output tracking data (See steps 308 through 319). 
     However, if the tracking level values decrease such as S 1  &lt;S 2  &gt;S 3  &gt;S 4  &gt;S 5  in the step 307, then (n-4), (n-8), (n-12), and (n-16) tracking data are generated in sequence. For each tracking data, the tracking level values S 6 , S 7 , S 8 , and S 9  are stored in the memory after the lapse of 0.1 second, each time. Thereafter, whether S 6  &lt;S 7  &lt;S 8  &lt;S 9  is checked, to detect a variation of the tracking levels (See steps 320 through 326). 
     Thereafter, if the tracking level increases such as S 6  &lt;S 7  &lt;S 8  &lt;S 9 , the tracking data are decreased by the system controller 6 by (n-4k), where k=5, 6, 7, . . . , 20, and then the current tracking level is compared with a preceding tracking level; as a result, if the current tracking level is lower than the preceding tracking level, the preceding tracking data is set as the output tracking data (See steps 327 through 339&#39;). 
     If the tracking level values decrease such as S 6  &gt;S 7  &gt;S 8  &gt;S 9  in the step 326, then the highest tracking level of the tracking level values S 1  through S 9  from memory is set as the output tracking data (See the steps 339 and 340). 
     Referring to FIG. 4, which shows tracking level values with respect to tracking data, a reference &#34;A&#34; represents the highest tracking level value, detected during the steps 308 through 319; a reference &#34;B&#34; represents the highest tracking level value, detected during the steps 327 through 339&#39;; and a reference &#34;C&#34; represents the highest tracking level value, detected during the steps 339 through 340. 
     Referring back to FIGS. 1 to 4, operation of an embodiment according to the present invention will now be described in detail. 
     With respect to the steps 301 to 306, the system controller 6 sets a variable k to zero in the step 301, and generates n+k initial preset tracking data in the step 302. In this case, the n+k (=n, since k=0) preset tracking data is supplied to the servo 7 together with a clock CK. Then, the servo 7 generates a capstan control signal CAP-CTL to the deck 1 according to the tracking data to control the capstan. As a result, the capstan in the deck 1 rotates to run a tape and at the same time a signal is read from the tape. Being very weak, this signal is preliminarily amplified by a preamplifier 2. Of various signals, the only signals required for tracking control are selected by the peaking process and amplified, up to or over 1 V, by an amplifier 4. The amplified signals are integrated by the integrator 5. The integrated signals become the tracking level and are applied to the analog-to-digital converter in the system controller 6, to generate a digital tracking level value S 1  (k=0; S.sub.(4+k)/4 =S 1 ). 
     That is, 0.1 second after the generation of n tracking data in step 302, the system controller 6 stores the tracking level value S 1  into memory. Consecutively, the system controller 6 checks whether the variable k is equal to 16 in step 305. In this case, however, since the variable k is zero, the system controller 6 proceeds to the step 306. 
     The system controller 6 then generates next n+k tracking dta and after the lapse of 0.1 second, stores in memory the tracking level value S 2  (k=4; S.sub.(4+k)/4) =S 2 ) for the n+4 tracking data. 
     In the above way, the system controller 6 repeats the steps 302 through 306 to generate the digital tracking level values S 1 , S 2 , S 3 , S 4 , S 5  for the respective n, n+4, n+8, n+12, n+16 tracking data, the above digital tracking level values being stored in the memory sequentially. When the variable k reaches sixteen (i.e., k=16), the system controller 6 will proceed to step 307 and analyze the tracking level values S 1 , S 2 , S 3 , S 4 , S 5  to determine whether they are in the order of S 1  &lt;S 2  &lt;S 3  &lt;S 4  &lt;S 5 . If the tracking level values are increasing as such, the system controller 6 proceeds to the step 308. 
     During the steps 308 through 319, if the tracking level values for the respective tracking data increasing sequentially by four steps are decreased at a certain point as shown with reference to a curve 401 of FIG. 4, the system controller 6 determines, a tracking data preceding a current tracking data as a highest tracking level valve. This procedure has been expanded and improved over the prior art so that the tracking level may be more precisely determined. 
     In the step 307, if the tracking level values are not increasing, then the system controller 6 proceeds to step 320 and sets a variable L to four (i.e., L=4). The system controller 6 generates n-L (i.e., n-4) tracking data in step 321 and stores in memory a digital tracking level value S.sub.(20+L)/4 (i.e., S 6 ) for the digital tracking data n-4, in step 323. In practice, the tracking level value S 6  is produced such that a tracking envelope signal output from the head in the deck 1 is processed through the preamplifier 2, peaking circuit 3, amplifier 4, integrator 5, and analog-to-digital converter in the system controller 6. Thereafter, whether the variable L is equal to sixteen (i.e., L=16) is checked in step 324; as a result, if the variable L is not equal to sixteen, the system controller 6 proceeds to the step 325, to increase the variable L by four and to repeat the above steps 321 to 324. In this way, the system controller 6 generates n-4, n-8, n-12 and n-16 tracking data and stores the digital tracking level values S 6 , S 7 , S 8  and S 9  for the above respective tracking data. If the tracking level values are in the order of S 6  &lt;S 7  &lt;S 8  &lt;S 9 , the system controller 6 proceeds to step 327. 
     In steps 327 to 339&#39;, if the tracking level values for the respective tracking data decreasing sequentially by four steps are decreased at a certain point as shown with reference to a curve 402 of FIG. 4, the system controller 6 determines the tracking data preceding the current tracking level value as the highest tracking level value. In this way, the system controller 6 compares the tracking level values, to determine the highest tracking level. Then, the system controller 6 sets the output tracking data to the digital data corresponding to the above highest digital tracking level value, thus continually sustaining an optimized tracking condition. 
     However, in step 326, if the tracking level values are not in the order of S 6  &lt;S 7  &lt;S 8  &lt;S 9 , then the system controller 6 proceeds to step 339 to compare the tracking level values S 1  -S 9  stored in the memory to detect the highest tracking level value. In the step 340, the system controller 6 sets the tracking data corresponding to the above highest tracking level value as the output tracking data. 
     It should be noted that the present invention is featured by the steps 339 and 340 in which the highest tracking level value can be detected even though the tracking level values are irregularly changed as shown with reference to the curves 403 and 404 of FIG. 4. 
     As described heretofore, the present invention monitors the variation of the tracking level to always detect the highest tracking level. Then, the tracking data corresponding to the highest tracking level value is set as the output tracking data, thus continually sustaining an optimized tracking condition. 
     The foregoing description shows only one preferred embodiment of the present invention. Various modifications are apparent to those skilled in the art without departing from the scope of the present invention which is only limited by the appended claims. Therefore, the embodiment shown and described is only illustrative, not restrictive.