JPH0115005Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a capstan motor control circuit for reproducing tapes in different recording modes in a predetermined reproduction mode.

In order to lengthen the recording time, cassette video tape recorders sometimes perform recording by cutting the tape speed by half at the expense of the clarity of the reproduced image. Therefore, when running such a recording tape by specifying a playback mode, it is necessary to change the running speed of the tape at the portion where the recording mode is changed. Figure 1 shows the frequency relationship between the control signal and the capstan rotation detection signal when a tape recorded in normal recording mode and a tape recorded in double long-time recording mode are played back normally and at double speed, respectively. This is an example of
As is clear from the figure, the recording mode can be detected by the frequency ratio of the control signal and the rotation detection signal.

In view of the above-mentioned points, the present invention proposes a novel capstan motor control circuit that changes the running of the tape according to the recording mode and realizes playback in a predetermined playback mode.

The present invention will be described below with reference to an illustrative embodiment.

This embodiment is a capstan motor control circuit that defines the relationship between the control signal and the rotation detection signal as shown in FIG. 1 by setting the playback mode, and FIG. 2 shows the circuit block of this embodiment. Reveal the figure. In the figure, number 1 is a rotation detection means for deriving a rotation detection signal a in relation to the rotation of the capstan motor M, and 2 is a rotation detection means that derives the rotation detection signal a and a reproduction control signal b based on the oscillation output c of the oscillation circuit 3. are counted by the rotation detection signal period counting circuit 2a and the playback control signal period counting circuit 2b, respectively, and the ratio of both counts is 1:1 (long-term recording tape) or 2:1.
A period comparison circuit (period comparison means) that determines whether the period comparison circuit 2 is a long-time recording tape (normal recording tape) by a count ratio determination circuit 2c, and 4 derives an output d that determines whether the period comparison circuit 2 is a long-time recording tape. A flip-flop 5 is reset when an output e is derived to determine that the tape is a normal recording tape, and a flip-flop 5 inputs mode selection signals g, h and the flip-flop output f, and controls three speeds of the capstan motor. Rotation speed specified output that changes to
Logic circuit (logic means) for deriving v ₁ , v ₂ , v ₃ , 6
7 is a rotation control circuit that defines the cycle of the rotation detection signal a based on the rotation speed designation outputs v ₁ , v ₂ , and v ₃ and derives the rotation control output r of the capstan motor, and 7 is a rotation control circuit that divides the oscillation output. 8 is a frequency divider circuit which derives a frame period reference signal f during normal playback and a field period reference signal f during double speed playback, and a time constant circuit 8 is changed by the mode selection signal gxh to derive the reference signal i and the reference signal f described above. SW represents a phase control circuit that compares the phases of the reproduction control signal b and derives the phase control output p of the capstan motor, and SW represents a mode selection switch. The period comparator circuit 2, the oscillation circuit 3, the flip-flop 4, the logic circuit 5, and the frequency divider circuit 7 express the functions of the microcomputer in hardware, and these circuits are implemented by the software of the microcomputer. Consists of clothing.

Therefore, when the mode selection switch SW is set to the normal playback side, the frequency divider circuit 7 derives a reference signal of the frame period, and the phase control circuit 8 determines the generation timing and timing of the reference signal in order to compare the phases of the frame period. The inclination angle of the comparison inclination section is changed by a time constant circuit. In addition, the logic circuit 5 operates at a second rotational speed when a normal recorded portion is being reproduced based on the output f of the flip-flop 4, which is set to a set state or a reset state depending on the recording mode, and a mode selection signal g. A designated output v ₂ is derived, and when a long-time recorded portion is being reproduced, a first rotational speed designated output v ₁ is derived. Furthermore, when the second rotation speed designation output v2 is input, the rotation control circuit ₆ sets the frequency of the rotation detection signal a to 60 Hz and controls the cap to run the tape at the same speed as during normal recording. Controls the rotation of the stun motor M,
When the first rotation speed designation output is input, the frequency of the rotation detection signal a is set to 30Hz, and the capstan motor rotates at the same speed as when recording a tape for a long time (i.e., 1/2 the speed of normal recording). control. Therefore, when the recording mode of the tape is changed during playback, the flip-flop 4 is reversed, and the rotation of the capstan motor M is automatically doubled or halved to perform normal playback.

Similarly, when the mode selection switch SW is set to the double speed playback side Q, the phase control circuit 8 changes the time constant circuit to perform a phase comparison of the field period, and the logic circuit 5 changes the time constant circuit to perform the phase comparison of the field period. 3 is derived, and a second rotational speed designation output _v2 is derived at the time _of long-time recording partial reproduction. Further, the rotation control circuit 6 causes the capstan motor M to rotate at twice the speed of normal recording using the third rotation speed designation output _v3 , and causes the capstan motor M to rotate at twice the speed of normal recording using the third rotation speed designation output _v2 . Therefore, the capstan motor M is rotated at twice the speed of long-time recording (same speed as normal recording). Therefore, the reproduced image to be displayed is in double speed reproduction mode.

FIG. 5 specifically shows the logic circuit 5 described above. The first AND circuit AD1 inputs the selection output h and the flip-flop output f during double-speed playback, and reproduces the normally recorded portion during double-speed playback. output that causes the tape to run at V ₃ (high speed). In addition, the second AND circuit AD2 inputs the selection output 9 during normal playback and the inverted output of the flip-flop, and generates an output that causes the tape to run at V ₁ (low speed) when a long recorded portion is being played back during normal playback. . Furthermore, when no output is generated from both AND circuits, that is, when the normal recorded part is being played back during normal playback, or when the long time recording part is being played back during double speed playback, the tape is output from the NOR circuit NR.
Generates output that allows the vehicle to run at V ₂ (medium speed).

In this embodiment, a circuit that performs only normal playback and double-speed playback is illustrated, but it goes without saying that special playback such as slow-motion playback can also be easily realized by appropriately changing the logic circuit and the like. Also,
In this example, we did not mention the specific configuration of the period comparison circuit, but since such a circuit is part of the software of the microcomputer, there is no point in disclosing the specific circuit configuration, so we will not discuss it here. Omit.

Furthermore, in this embodiment, the phase comparison control circuit executes phase control in accordance with the cycle of the reproduction control signal, but for example, when executing only normal reproduction and double speed reproduction as in the embodiment, the capstan Since the rotational speed change amount remains within the range of 1:4 at most, it goes without saying that the control signal may be appropriately frequency-divided in order to keep the phase comparison period constant.

As mentioned above, according to the present invention, since the tape speed is changed in accordance with the change in the recording mode and the playback mode is kept constant, there is no need to change the tape speed every time the recording mode is changed, and the effect is is large.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating the relationship between a reproduction control signal and a rotation detection signal for recording mode and reproduction mode, and FIG. 2 is a block diagram of an embodiment of the present invention. Explanation of main drawing numbers, 1...Rotation detection means, 2...
Period comparison means, 5...Logic means, 6...Rotation control circuit.

Claims (1)

[Scope of Claim for Utility Model Registration] Rotation detection means for detecting the rotation of a capstan motor, and each cycle of the output of the rotation detection means and a reproduction control signal is counted by a constant oscillation output, and the ratio of the two counted values is calculated. a mode selection switch for setting a playback mode; and logic for inputting each output of the period comparison means and the selection switch to specify the rotational speed of the capstan motor. A capstan motor control circuit comprising: a means for controlling a rotation speed of the capstan motor; and a rotation control circuit for controlling the rotation speed of the capstan motor based on an output of the logic means.