JPS62146453A - Tracking circuit - Google Patents

Abstract

PURPOSE:To reduce the number of UP/DOWN switches only to a pair by providing a tracking circuit with a limiter for connecting counters strong a normal reproducing delay time and a slow reproducing delay time respectively and an UP/DOWN switch selectively to a counter. CONSTITUTION:A signal is sent from a remote control decoder 31 to OR gates G1-G4. When a system controller 17 outputs a signal F1 by a signal outputted from the gate G3, the limiter 19 is connected, the output of the gate G1 is transmitted to a counter 3a and the output 23 of the counter 3a is inputted to a normal reproducing monostable multivibrator 8a through a switching device 22, a D/A converter and contacts Sc-Sa of a switch 22. A tracking delay time is determined by the contents of the counter 3a. The D/A converter 5 consists of an analog switch S and a divided resistor R and the counter 3 generates a signal of 5 bits by a preset value 4 and the selection of the switches 1, 2, shorts the divided resistor selectively, changes a time constant, and changes the delay time of the monostable multivibrator 8. In such constitution, it is unnecessary to prepare two pairs of tracking adjusting means such as UP/ DOWN counters.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial application field The present invention is applicable to a video tape player (VT) having a playback function.
This invention relates to a tracking circuit for a videotape player such as R).

(b) Conventional technology When a videotape is played back using a VTR, a tracking servo is applied. This tracking servo is performed using a reproduction control signal or the like as a reference. However, when playing back a videotape recorded on another VTR, or when playing back a videotape that has been expanded due to aging, there is a risk that tracking will shift. For this reason, the VTR performs tracking adjustment by varying the amount of delay (delay time) of the reference signal corresponding to the rotation of the reproduction control number or rotary head.

An example of this tracking servo will be explained with reference to FIGS. 4 and 5.

During reproduction, this circuit uses the control signal reproduced by the control head (CTL head) (55) and the reference oscillation circuit (54) for driving the head motor (51).
Tracking correction is performed using the 30Hz standard No. 18 from ).

The correction method is based on the standard 18 in the tracking delay section (56).
The comparator circuit (59) outputs the CTL pulse (5
8), the speed and phase of the capstan motor (57) are controlled by comparative detection and feedback.

In order to adjust the amount of correction, the tracking delay section (56
), this can be done by changing the delay time of the reference signal, and for this purpose the VTR's operating section is equipped with a tracking knob. There are rotating and sliding types of knobs. This tracking delay section (56) uses a monomulti circuit to delay the reference signal, and uses the C-R integral time constant to change the delay time by making the resistor R a variable resistor. ing.

Fig. 5 shows an outline of the mono multi circuit forming the tracking delay section. In Fig. 5, <61> is the mono multi IC, (63) is the variable resistor (tracking volume), (64) is Hundenzer.

In addition, (62), (63), and (64) constitute a time constant circuit,
Determine the delay time (pulse width) in the monomulti IC (61).

The above operation will be explained. As can be seen from FIG. 4, the head motor (51) rotates in synchronization with the reference signal from the reference oscillation circuit (54). And the capstan motor (57
) rotation (tape running) is synchronized with the rotation of the video head using a reference signal. Therefore, the video head can always scan directly above the video track. Also, other V
A tracking delay section (56) is provided for compatibility with video tapes recorded with TR. Tracking 1
At the time of llt, the user directly adjusts the variable resistor (63) in FIG. 5 while viewing the reproduced image so that the reproduced image becomes the best. Or, Utility Model Application No. 1982-165009, Utility Model Application No. 59-139503, and JP-A-56-78282
As shown in the figure, the variable resistor (63) is directly adjusted to maximize the reproduction envelope output.

In the conventional example described above, trunking adjustment was performed by varying the delay amount of the reference signal (signal corresponding to the rotational phase of the video head). Sometimes it can be adjusted. Further, tracking control is performed not only during normal playback but also during intermittent slow playback, for example. Incidentally, during this intermittent slowing, a brake pulse is generated by a regeneration control signal, and the amount of delay of this regeneration control signal is varied.

Regarding this tracking servo, please refer to pages 136-141 of 1 TV GOGEN Society Practical Book Series ``Introduction to Home VTR'' published by Corona Publishing, and ``Introduction to VT RJ Nop 105, p 1181)'' published by Tokyo Denki University Press, 119.
This is a very well-known configuration described in various documents such as p192 p193 and Japanese Utility Model Application No. 122148/1983.

As shown in the above-mentioned document, the tracking adjustment resistor for normal tracking i*t is composed of a variable resistor.

However, as shown in Utility Model Registration 3M (12) filed by the applicant on November 20, 1985, there is a VTR that adjusts tracking using up and down switches. In this VTR, if the up/down switch is provided on the remote control transmitter, the user can conveniently adjust the tracking at hand.

By the way, tracking IT is performed during normal playback and slow playback. For this reason, the VTR's 1)
There is an up/down switch for adjusting tracking 11 during slow playback, and a tracking adjustment TM during normal playback.
Two pairs of up-down switches are required.

For this reason, as shown in JP-A-57-422785J or the utility model registration application (10) filed by the applicant on October 23, 1985, tracking adjustment for slow playback and normal playback is performed in one. It is also possible to use a variable resistor. However, adjusting them separately is more resistant to deterioration over time and the occurrence of errors.

(c) Problems to be Solved by the Invention In a VTR that performs tracking adjustment separately during slow playback and normal playback, it is necessary to provide two tracking allt means such as up/down switches.

(2) Means for Solving Problems The present invention provides a counter (first storage means) during normal playback that stores the delay time of the tracking delay section during normal playback (first playback mode), and a counter (first storage means) for slow playback. A slow playback counter that stores the delay time of the tracking delay section (in the second playback mode)
a second storage means) and a mink circuit selection means that connects the up-down switch (U!4 adjustment means) to the counter for normal playback during normal playback and connects the up-down switch to the counter for slow playback during slow playback. ).

(E) Function Since the present invention has the above-described configuration, the count value of the V counter is varied during slow playback to adjust tracking during slow playback, and during normal playback, the count value of the V counter is changed to adjust tracking during slow playback. The count value of the counter used for adjustment is varied. Therefore, up-down〉・
There is no need to provide two pairs of switches.

(f) Embodiment An embodiment of the present invention will be described with reference to FIGS. 1 to 3.

First, the tracking delay section is shown in Figure 2. In Figure 2, (3) is a 5-bit up/down counter.
It is preset to "15" by the initial setting circuit (4).

(1) is an input switch for up-counting, (2) is an input switch for down-counting, b1 to b5 are the binary outputs of the 5-pit counter (3), and bl is the least significant bit. 5) is a circuit that converts a digital value into a resistance value (hereinafter referred to as the D-R conversion circuit). This part is an analog switch (Sl) consisting of a relay or 0MO8 IC.
~(S5) and divided resistors (R1)~(R5). Each resistance value is R2-2・R with R1 as a reference.
1, R3 depth 4・R1, R4■8・R1, R5-16φR
1, and the example selected R to be about 100 ohms. (6) is a capacitor. When the output of the counter (3) is "31", the resistor (7) is connected to (R1) to (R5).
) is short-circuited by the switches (Sl) to (S5) to prevent the resistance component from becoming zero.

Generally, it is sufficient for the tracking delay time to be ±10 milliseconds from the center value, and the range of variation thereof may be about 1 millisecond. Also, if the intermediate value of the counter is ``15'', then ±1
A variable width of 5 steps is obtained. Therefore, about 0.7 per stage
It was designed to have a variation width of milliseconds. Also counter (3
) is '15'', the delay time of monomulti (8) is 3
3.3 milliseconds.

Note that 33.3 milliseconds corresponds to one period of the reproduction control signal.

The input circuit of the counter (3) has a limiter circuit not shown in Figure 2, which prohibits up-count input when the count value reaches "31" and inputs down-count input when the count value reaches "0". In other words, this counter is configured to count up and down between "0" and "31".It is easier to use when the tracking delay amount is set to the middle in the standard state during playback. Also VTR
During manufacturing, it is necessary to be able to set the intermediate value immediately due to various adjustments, so the counter (3) is set to the intermediate value (standard position, "15'") by a signal from the initial setting circuit (4).
) can be preset.

The initial setting circuit (4) operates in the following cases.

A. When the t* of "/TR" is inserted. A. When a cassette tape is inserted or removed. C.1. Although not shown in the figure, this is a case where the reset circuit is activated.

The initial setting circuit (4) has an important role and allows the standard tracking position e (reference position) to be easily set.
It can save time in adjusting and inspecting the VTR manufacturing stage.

The operation is as follows.

When the counter (3) is preset to "15" by the initial setting circuit (4), the outputs (bl) to (b4) become "H" level, and (b5) becomes "LIT level". Analog switches (Sl) to (S5) output (bl) to (b5
) is designed to close the 'H' level. Therefore, the analog switches (Sl) to (S4) are closed (the analog switch (S5) is open, so only the resistance (R5) acts as a time constant, and the combined resistance is R5) + (7).
becomes the resistance. , For convenience of explanation, if we proceed without the resistor (7), the tracking delay time will be [value of resistor (R5) x value of capacitor (6) 1 second].

Next, operate the up/down switches (1) and (2) to lower the counter (3) by 77 or lower, and the output (bl
) to (b5) become "H" or "L" level depending on the content, so the series combined resistance value of the resistors (R1) to (R5) that are not shorted by the analog switches (Sl) to (S5) is The time constant is R minutes. This is a mechanism in which the resistance reaches its maximum value when the count is "0", and the amount of delay is also maximized.

Next, FIG. 1 will be explained. FIG. 1 shows an example in which the circuit shown in FIG. 2 is incorporated into an actual VTR, which is provided with two counters (3a) and 3b for slow playback and normal playback. It also has two monomultis (8a) (8b).

The playback switch (11) and slow switch (12) are VT
This is the R operation switch. OR Age--(13), (1
4) is the up signal (
34), input the down signal (35). OR gate (
15) and (16) input the reproduction signal (36) and slow signal (37) from the remote control decoder (31).

(17) is a system controller (hereinafter referred to as system controller), which uses the reproduction signal from the OR gate (15) to
While setting the TR to the playback mode, the playback mode signal (Fl
) to enable trunking adjustment for normal playback. The system fan (17) puts the VTR in slow mode using the slow signal from the OR gate (16), outputs the slow mode signal (F2), and enables tracking adjustment for slow playback. Additionally, pause signals, fast-forward signals, stop signals, etc. are also input to this system controller (17).
Although the TR is controlled, this is not shown in the drawing.

This signal (F 1) (F 2) operates the limiter circuit <19) (20) which is the gist of the present invention.

The limiter circuit (19) is made conductive by the reproduction mode signal (Fl), and the up-down signal is sent to the counter (3) for normal reproduction.
a), and its output (23) is sent to the output switching circuit (2
1) becomes the output (25), and the D-R conversion circuit (5)
and is converted into a resistance value. There is also a changeover switch (2
2) is when 5c-8a is closed and the mono multi for normal playback (8
a), so the tracking delay time is determined by the contents of the counter (3).

When the slow mode signal (F2) is generated, the limiter (20) becomes conductive, the slow counter (3b) is selected and becomes the output (24), and the output switching circuit (21)
The signal passes through the D-R conversion circuit (5), is converted into a resistance value, and the selector switch (22) closes the connection between 5c and Sb and is input to the intermittent slow playback monomulti (8b).

The contents of the counters (3a) and (3b) can only be changed by up/down signals, except that they are preset to an intermediate value of "15" by the initial setting circuit (4), so they are used for temporary tracking adjustment. [The slow counter (3b) operates], and the normal playback counter (3a) retains its contents, so the previous tracking state can be reproduced even when normal playback is performed next time.

Next, we will discuss remote control operations.

(33) is a transmitter, and this part has push buttons necessary for operating the VTR as well as buttons for tracking adjustment, for up-counting and down-counting, respectively.

The transmission system uses a pulse code modulation method, which is known in many cases, but is not particularly limited to this method. After being amplified by an infrared light receiving section (32), it is decoded by a decoder circuit <31) and a necessary signal is output.

Next, the tracking display device will be described.

(41) is a microcomputer, and (42) has a function of generating a text information video signal (47) corresponding to the content such as characters and figures to be displayed on a TV screen character generation circuit.
(43) is a sync separation circuit, which separates the component video signal (
(44) extracts horizontal synchronization (H3) and vertical synchronization (VS) signals from (46), and (44) mixes the original video signal (46) and text information video signal (47) to generate a text multiplex video signal (45). ).

In addition, there is a simple way to project characters and figures on the TV screen.
Many have been published. Further, since the character generation circuit is sold as an LSI, its explanation will be omitted.

The output of the counter (25) is input to the microcomputer (41), and the reproduction mode signal (Fl) is input as the identification signal of the counter.6 Although not shown in the figure, an OR gate (
13) The signal in (14) is input as the display start signal for tracking adjustment.

Usually, tracking information is not displayed on the TV screen, decoder <31) or up/down switch (1
), (2) when the up/down signal is output, the microcontroller (
41) detects this and starts to output information on the TV screen as a tracking adjustment start signal.

As shown in Figure 5, the display shows the word "TRACKING" (
71) to indicate which operation it is. Marks (73) and (74) are displayed on the left and right to indicate the range (72) in which tracking can be adjusted and its direction.

Next, the content of the counter (25) is calculated and a mark (75) indicating its position is displayed. These operations are performed quickly.

Since the mark (75) moves left and right according to the contents of the counter, its position can be sequentially indicated by performing tracking adjustment.

Also, if this display is constantly displayed on the TV screen, it is an eyesore, so in the present invention, if the counter input signal does not continue for about 5 seconds or more, the tracking information display is controlled by the microcontroller 41) so that it disappears from the screen. ing.

As described above, in the present invention, the contents of the counters (3a) (3b) are communicated to the user by the marks (75). Therefore, the user operates the up/down switches (1) and (2) to
- When performing racking adjustment, put the VTR in normal playback mode and first move the mark (75) to all positions within the range (72). At this time, the user memorizes the position of the mark (75) that he or she considers to be good. And this range (7
2) After moving the mark <75) to all positions in
> to end the tracking adjustment during normal playback.

Next, set the VTR to slow playback mode and perform the same operation to track yj! during slow playback. At this time, the TV screen displays “SLOW TRACK I”.
NG” is displayed.

In the embodiment shown in FIG. 1, the limiters (19) and (20) set the upper limit of the counters (3a) and (3b) to "31" and the lower limit of "0".
) may change cyclically, such as "O" → "31" or 31" → "0", and in this case, the up/down switches (1) and (2) are set to one side. Tracking adjustment can be done just by using this method.

Further, in the above embodiment, the delay time may be varied by ±10 milliseconds.

In addition, in the above embodiment, counters (3a) (3) are displayed on the TV screen.
Although the value b) (corresponding to the amount of tracking deviation) is displayed, this may be displayed on, for example, an audio level meter of a VTR.

Furthermore, the playback envelope output may also be displayed.

In addition, in this embodiment, tracking 11 adjustment was described for two cases: slow playback and normal playback, but if counters are provided for fast forward playback, slow playback, and reverse playback, it will be possible to improve tracking in each case. It is possible to perform accurate tracking 11t.

(g) Effects of the Invention As described above, according to the present invention, tracking adjustment for different playback modes can be performed using one adjustment means, which is useful.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention. FIG. 2 shows the tracking delay section, and FIG. 3 shows the display state of 17 screens. FIG. 4 is a diagram showing an example of a conventional tracking servo, and FIG. 5 is a diagram showing a conventional tracking delay section. (23)・Output (first delay time setting signal), (3a)・
・Counter for normal playback (first storage means), (24>
...Output (second delay time setting signal), (3b)...
Counter for slow playback (second storage means), (8a) (
8b)...Mono multi〈Delay means L(1)...Switch for count amplifier (adjustment means), (2)...Switch for countdown (adjustment means), (19) (2
0)...Limiter circuit (3g selection means).

Claims (1)

[Claims] (1) In a videotape player that performs tracking adjustment by varying the delay time of a playback control signal or reference signal from a videotape, a first delay time setting signal that determines the delay time in a first playback mode. a second storage means that stores a second delay time setting signal that determines the delay time in the second playback mode; and a second storage means that stores the first delay time setting signal in the first playback mode. a delay unit that delays the reproduction control signal or the reference signal based on the signal, and delays the reproduction control signal or the reference signal based on the second delay time setting signal in the second reproduction mode; adjustment means for increasing and/or decreasing the value of the first and second delay time setting signals stored in the second storage means; the adjustment means being connected to the first storage means during the first reproduction mode; A tracking circuit comprising: selection means connected to the second storage means during a second reproduction mode.