Tape position detection apparatus having start control function

Abstract: A tape position detection apparatus is disclosed wherein a tape is first fed in a forward direction from one reel to another for a predetermined period of time, under the control of a tape transit control circuit (88). When the reels rotate, respective pulse genera­ tors (38, 40) generate pulses, which are counted by corresponding reel counters (42, 44). The counting period are set by control circuits (46, 48), and upon completion of a counting period, the count obtained is stored as first count data in a memory circuit. Also, as a capstan for feeding the tape rotates, a corre­ sponding pulse generator (64) generates pulses which are counted by capstan counters (60, 62). In accordance with the count, an operational circuit (68) calculates the residual amount of tape for presentation on a display (78). In the meantime, upon completion of the first counting period described above, the tape is fed in the reverse direction by a logic control circuit (50), during which time the count obtained when the tape was fed in the forward direction is compared, in a comparison circuit (52), with the count obtained when the tape is fed in the reverse direction. When the count data being compared become substantially equal, the tape is stopped.

Description: This invention relates to a tape position detection apparatus and, more particularly, to a tape position detection apparatus for detecting the position of a tape or a film wound on reels in a video or audio tape recorder. The conventional video tape recorder uses a tape position detector to confirm the running position of the loaded tape. In order for the tape position to be detected by such an apparatus, the tape is first run for a predetermined period of time. Data relating to the speed or frequency of rotation of at least the reels, on which the tape is wound, is obtained by the detector, and is substituted in a predetermined equation for calculation. Thus, in the case of the above video tape recorder, the tape position cannot be calculated unless reproduction a fast feed, or a rewind operation is first carried out immediately after the cassette tape has been loaded therein. The rotation of the reels, however, is considerably unstable in case when the reels are not rotated by more than one rotation due to the excentricity of the reels and the state, in which the tape is wound on the reels. In order to determine the tape position with accuracy, therefore, it is necessary to wait at least until the reels complete one rotation. This means that in case of a reproduction mode, particularly of a tape where data is recorded in a long time mode, a considerable time is required until the display of the tape position is obtained. Actual tape position display in a VHS format video tape recorder requires time as follows. With a cassette tape loaded in the video tape recorder, a time from the instant of start of tape loading caused by depressing a reproduction key till the instant when the tape position display is obtained, is measured. The measured time is approximately 15 seconds with a tape where data is recorded in a standard mode and approximately 30 seconds with a tape where data is recorded in a long time mode. When the forward/reverse high speed reproduction mode, which is also known as the fast forward/reverse reproduction mode is employed in order to determine the tape position, the tape position can be displayed sooner than in the case where the normal reproduction mode is used. This is because in the fast forward/reverse reproduction mode, the tape is fed about five times faster than in the case of the normal reproduction mode. However, the tape is fed up to a position, which is considerably spaced apart from the position before the start of fast forward/reverse reproduction, and it has to be returned, manually, to the initial position, which is a time-consuming operation. As has been shown, detecting the tape position by means of the prior art tape position detection apparatus is a relatively lengthy process and requires returning the tape to its original position prior to the commencement of the position detection operation. Moreover, it cannot be guaranteed that the tape will be returned to its exact pre-detection position. As a result, it has, until now, not been possible to satisfy the demand of being able to confirm the tape position or residual tape amount immediately, after the loading of the cassette tape into a recorder. Prior art document DE-A-2 853 025 discloses a tape position detection apparatus comprising tape drive means which feed a tape in either forward or reverse direction, means for controlling the feed, detecting means, means for calculating the used amount of tape, and display means. In this apparatus the tape is returned to the start position, and the tape position is determined by transporting the tape a predetermined distance and thereafter returning the tape to the start position. Further, prior art document DE-A-3 318 324 which is considered to represent the closest prior art describes a tape position detection apparatus comprising feeding means, first and second detecting means for the supply and take-up reels, first and second counting means, first and second control means, a capstan for feeding the tape, calculating means, display means, a logic control circuit, and third detecting and counting means for the capstan. To determine the tape position it is necessary to transport the tape at least one reel rotation thereby moving the tape and the reproducing recording head away from the start position. It is an object of the present invention to provide a tape position detection apparatus, which can quickly meet the demand of being able to confirm the tape position, and in which the tape having been fed for the detection of the tape position can be readily returned to the initial position. This object is met by the present invention which is defined in the appended claims. Features of the present invention will become more apparent from the following detailed description of exemplary embodiment thereof, as illustrated in the accompanying drawings, in which: Fig. 1 is a schematic representation of a video tape recorder tape running system incorporating a tape position detection apparatus according to the invention; Fig. 2 is a block diagram showing the construction of the tape position detection apparatus according to the invention; Fig. 3 is a block diagram showing part of a video tape recorder of the type, in which the residual amount of tape is displayed by a subtitle device on a display as shown in Fig. 2; and Fig. 4 is a perspective view showing a television receiver, in which the residual tape amount is displayed by the subtitle device shown in Fig. 3. An embodiment of the present invention will now be described, with reference to the drawings. Fig. 1 shows a tape running system of a video tape recorder incorporating one embodiment of the tape position detector according to the invention. Supply reel 12 and take-up reel 14 are housed in a video tape cassette (not shown). Tape 20 is wound on hubs 16 and 18 of reels 12 and 14. When the cassette tape is inserted in the video tape recorder, reels 12 and 14 engage with corresponding reel bases (not shown). Tape 20 is fed from one reel to the other as reel bases are rotated in a predetermined direction by either supply reel drive motor 122 or take-up reel drive motor 124. When the video tape recorder is in either the recording mode or the reproducing mode, tape 20 is passed round cylinder 26 having rotary heads. This is effected by predetermined operations of tape guides 28 and 30. The feeding of the tape begins when tape 20 is urged against capstan 36 by the pinch roller 32, and capstan 36 is then rotated by capstan drive motor 362. Pulse generator 38 comprises a rotary disk 38a and a magnetic sensor 38b, pulse generator 40 comprises a rotary disk 40a and a magnetic sensor 40b. Either rotary disk has a plurality of magnets (six magnets in this embodiment) on its circumference. Generators 38 and 40 generate respective supply reel 12 and take-up reel 14 rotation detection pulses, which are supplied to respective reel counters 42 and 44. The counting period and timing of reel counters 42 and 44 are controlled by control circuits 46 and 48, respectively which operate in accordance with control signals supplied by logic control circuit 50, which controls the video tape recorder tape running system. The outputs of reel counters 42 and 44 are supplied through comparating circuit 52 to memory circuit 54. The outputs supplied to memory circuit 54 is used as memory data or comparison data. The outputs of reel counters 42 and 44 are supplied to respective control circuits 56 and 58, which control the counting operation of capstan counters 60 and 62 during a period corresponding to a predetermined value of the input count. Pulse generator 64 produces a rotation detection pulse representing the rotation of capstan motor 362 which drives capstan 36 in order to feed tape 20. The output of pulse generator 64 is supplied to capstan rotation counters 60 and 62. Pulse generator 64 has the same structure as pulse generators 38 and 40, i.e. , it comprises a rotary disk 64a and a magnetic sensor 64b. The count outputs of capstan counters 60 and 62 are supplied to respective operational circuits 66 and 68. These count outputs are utilized in operational circuits 66 and 68 as data for determining the type of tape being used and residual tape amount, and are also supplied to memory circuits 70 and 72. For the calculation of the residual amount of tape, it is necessary to change parameters depending on the kind of tape. Tape-type discrimination signal generator 74 is coupled to operational circuit 66, discriminates the type of tape being used. Operational circuit 68 is coupled to tape speed signal generator 76 which generates, to find a residual tape amount, the identification of a class into which the current tape speed is classified. (If recording or reproduction is performed in SP mode, for instance, the tape speed signal generator identifies the current tape speed mode as an SP mode.) Display 78 for displaying the residual amount of tape is coupled to operational circuit 68. For the control of the tape-running system, the output signals from tape residual amount quick display on-off signal generator 80, cassette detection signal generator 82, loading detection signal generator 84 and tape-end detection signal generator 86 are supplied to logic control circuit 50. Tape residual amount quick display on-off signal generator 80 produces an on-off signal concerning the display (quick display) of the residual amount of tape in an interlocked relation to the loading of the cassette tape to be described later. It is not always necessary to effect display of the residual amount of tape at the time of the loading of the cassette tape. Therefore, whether or not to effect the display is determined by the user. The output of signal generator 80 is supplied to logic control circuit 50. Cassette detection signal generator 82 produces a signal as to whether there is a cassette loaded in the video tape recorder. Therefore, when the signal generator 82 does not supply any cassette detection signal to logic control circuit 50, no drive motor is operated, that is, neither reproducing nor recording operation as the tape running system is caused. Loading detection signal generator 84 produces a signal as to whether the tape is loaded when the tape cassette is loaded in the video tape recorder. When the detection signal of signal generator 84 is supplied to logic control circuit 50, the system is rendered to be in a residual tape amount calculation mode. Tape-end detection signal generator 86 produces a detection signal when tape 20 has been completely wound on a reel (i.e., either supply or take-up reel) in the reproducing, recording, fast forward or rewind operation. It is also coupled to operation circuit 68. Logic control circuit 50 controls the tape-running system as follows according to the input data as noted above and also to prevailing state of control of the system. The prevailing state may be the rewind of tape 20, stationary state, reproducing state, etc. The control noted above is under-taken by tape transit control circuit 88, which is coupled to logic control circuit 50. To logic control circuit 50 is further supplied a mode-setting signal from a tape position detection setting circuit 90, which sets various modes, e.g., reproduction of tape 20, take-up, stop, for the tape position detection. Now, an example of the operation of the video tape recorder having the above construction will be described. When a cassette tape is loaded in the video tape recorder, logic control circuit 50 first effects loading of the cassette tape. Then, tape position detection setting circuit 90 supplies a setting signal to logic control circuit 50 to specify a fast forward reproduction mode of the tape-running system for the tape position detection. Logic control circuit 50 then controls the tape-running system to be in the fast forward reproduction node by having tape 20 to be urged against capstan 36 by pinch roller 32. At the same time, it causes reel counters 42 and 44 having been preset to be set in a measuring mode via control circuits 46 and 48. Thus, pulse generators 38 and 40 for detecting the rotation of respective supply and take-up reels 12 and 14, produce pulses with the rotation of the supply and take-up reels, these pulses being supplied to reel counters 42 and 44. While supply and take-up reels 12 and 14 execute one rotation, pulses produced from pulse generator 64 for detecting the rotation of the capstan 36 are supplied to capstan counters 60 and 62 for counting. At the same time, the counts of reel counters 42 and 44 at the time of the fast forward reproduction noted above are supplied through comparating circuit 52 to memory circuit 54 to be stored in the same. Thus, the contents of the data in capstan counter 60 correspond to the extent of tape feed while supply reel 12 executes one rotation. Likewise, the contents of the data in capstan counter 62 correspond to the extent of tape feed while take-up reel 14 executes one rotation. The data of capstan counters 60 and 62 are supplied to operational circuit 66. Operational circuit 66 discriminates the type of tape (i.e., time based on tape length) utilizing the output signal of tape-type discrimination signal generator 74. The data indicating the type of tape is supplied from operational circuit 66 to operational circuit 68, and tape speed signal generator 76 supplies to operational circuit 68 a speed mode signal for calculating the residual tape amount. Operational circuit 68 is further supplied with the count data from counters 60 and 62. All of the data thus supplied to operational circuit 68 is used for the calculation of the residual tape amount. At the same time, the mode of the tape-running system is switched over to a rewind mode by tape transit control circuit 88. In the rewind mode, tape 20 is rewound until the count of reel counters 42 and 44 becomes equal to the count obtained at the time of the fast feed reproduction or a value obtained by adding a predetermined correction value to the count at the time of the fast feed reproduction. The count data of reel counters 42 and 44 at the time of the fast forward reproduction have been stored in memory circuit 54, and data at the time of the fast forward and that at the time of the rewind are compared in comparating circuit 52. The output of comparating circuit 52, representing the result of comparison of counts, is supplied as detection signal to logic control circuit 50. Then, tape transit control circuit 88 controls the tape-running system to a stop mode to stop motors 122, 142 and 362. Now, the method of calculation of the residual amount of tape, will be described. For the calculation, the type of tape is first discriminated by obtaining the radius Rs and Rt of the tape rolls on supply and take-up reels 12 and 14. The tape roll radius Rs is given as follows: Rs = Radius of capstan (Number of capstan FG pulses per rotation of capstan) × (Number of capstan FG pulses per rotation of supply reel) The tape roll radius Rt, like Rs, can be obtained in the same manner as equation (1). Then, there holds the following relation: Rs² + Rt² = L·t π + 2Ro² where L is the total tape length, t is the thickness of the tape and Ro is the hub radius. The term Rs² + Rt² has a peculier value determined by the type of tape 20. It is thus possible to discriminate types of tapes of different values of hub radius Ro. Long-time tapes which exceed 120 minutes in recording time when used in SP mode have different thicknesses. The long-time tapes have reduced thicknesses for accommodation in the cassette, because tapes having different recording times are accommodated in cassette having a fixed size. The thickness of tape 20 is thus specified by specifying the type of tape 20. This specification is provided from tape kind discrimination signal generator 74. The residual tape amount time Tl is represented by either one of the following two well-known equations: Tl = π(Rs² - Ro²) tv or, where v is the tape speed at the time of the recording, and ω is the angular speed of reel. The residual tape amount time Tl can be calculated by using either one of equations (3) and (4). Of these equations, equation (4) permits calculation of the residual tape amount even if the extent of tape feed is not known provided the tape speed is constant. Thus, once the tape type is discriminated, it is possible to detect the tape position by causing the fast forward or reverse of tape without urging the tape against the capstan. Now, modifications of the above embodiment will be described. In the above embodiment, the residual amount of tape is calculated and displayed on display 78 while the tape is being fed in one direction (in the first forward reproduction or reverse reproduction mode). In addition to this method of calculation, the residual amount of tape may be calculated in both the fast forward reproduction and reverse reproduction modes, and the average value of the calculated values may be displayed as the residual amount of tape on display 78. In this case, the accuracy can be improved compared to the above embodiment. Where the residual amount of tape is displayed in the average value, at the time of the end of the fast forward or reverse reproduction the result may be displayed, and at the time of the end of the calculation in the reverse or fast forward reproduction the average value of both the calculation results may be displayed. By so doing, it is possible to further reduce the time required from the start of the measurement till the display of the residual tape amount. Further, in the case of the video tape recorder a television receiver is usually connected. Therefore, it is possible to display the residual tape amount along with other image on the receiver screen. The residual tape amount data obtained in operational circuit 68 is supplied to character decoder 92, as shown in Fig. 3. Character decoder 92 converts the residual tape amount data into character data. The character data obtained from the residual tape amount data is supplied to subtitle device 94. To subtitle device 94 is supplied a video signal from a well-known video tape recorder. Subtitle device 94 comprises a character superimposition circuit to superimpose the display character data on the video signal input to the video tape recorder. Further, an audio signal from the video tape recorder is supplied to RF modulator 96. RF modulator 96 receives an output signal from subtitle device 94 and supplies an RF signal to a television receiver. Subtitle device 94 supplies a video signal to the television receiver for the display of the image and residual tape amount data. Fig. 4 shows an example of such television receiver. On screen 100 of television receiver 98 image from the video tape recorder is displayed by the video signal noted above. The residual tape amount is displayed by character display on a portion, e.g., a lower portion, of screen 100. In the Figure, subtitle 120 indicates that the residual tape amount corresponds to one hour and 20 minutes. If such television receiver 98 where the residual tape amount is displayed in the above manner is used such that the residual tape amount is displayed as subtitle 120 on screen 100 for a constant period of time, e.g., 3 seconds only at the time of the video tape recorder tape detection as noted above, it will be very convenient for the user. In such a video tape recorder, the tape position display can be obtained in a short period of time, e.g., 8 seconds, form the start of the tape loading. It should be noted that the residual tape amount display method employed in each of the above embodiments is not necessarily connected with a tape cassette charging operation but may be started when a tape cassette is already charged and is in a stop condition.

Claims: A tape position detection apparatus having start control function comprising first and second feeding means (122, 142) for feeding a tape (20) in a first and second direction respectively, from one reel (12) to another reel (14), first and second detecting means (38b, 40b) for detecting the rotation of said respective reels (12, 14) and generating corresponding pulses, first and second reel rotation counting means (42, 44) for counting said pulses generated from said first and second detection means (38b, 40b), first and second control means (46, 48) for setting a counting period of said first and second reel rotation counting means (42, 44), memory means (54) for storing the output of said first and second reel rotation counting means (42, 44) as a first count after the lapse of said counting period during which said tape is fed in either said first or said second direction, a capstan (36) for feeding said tape (20) urged against it in reproducing and recording modes, logic control circuit (50), third detecting means (64b) adapted to detect the rotation of said capstan (36) and generate corresponding pulses, third counting means (60, 62) adapted to count said pulses generated from said third detecting means (64b), calculating means (66, 68) adapted to calculate the position of said tape (20) or the used or residual amount thereof based on the output of said first to third counting means (42, 44, 60, 62), display means (78) adapted to display the position of the tape (20) or the used or residual amount thereof, characterized in that said logic control circuit (50) is adapted to stop said tape (20) after the lapse of said counting period, and thereafter feed said tape (20) by said first or second feeding means (88) in a direction being opposite to the tape feeding direction during said counting period, comparing means (52) is adapted to compare a second count provided from said first and second reel rotation counting means (42, 44) with said first count stored in said memory means (54), and when said first and second counts become substantially equal to each other, said logic control circuit (50) is adapted to stop said tape (20) being at the position before it is fed in the tape feeding direction during said counting period, wherein: while the tape (20) is being fed in the first or second direction being a direction opposite to the tape feeding direction during said counting period, the tape position or the used or residual amount thereof is calculated, so that the tape position or the used or residual amount of tape (20) is calculated in both forward reproduction and reverse reproduction modes, and the average value of the calculated values can be displayed. An apparatus according to claim 1, characterized in that said first and second feeding means (8) are rendered operative in forward and reverse high speed reproduction. An apparatus according to claim 1 or 2, characterized in that said counting period is a period required for one rotation of said reels (12, 14).

Inventors: IZAWA FUMIO PATENT DIVISION, UTSUNOMIYA MASAAKI PATENT DIVI, IZAWA, FUMIO PATENT DIVISION, UTSUNOMIYA, MASAAKI PATENT DIVISION
Applicants: TOSHIBA KK, KABUSHIKI KAISHA TOSHIBA
Application year: 1988
Main classification: G11B27
IPC codes: G11B27