Transfer control device for a reproducing transducer in a rotary recording medium reproducing apparatus

A transfer control device for a reproducing transducer in a rotary recording medium reproducing apparatus having a reproducing transducer for reproducing recorded signals from a rotary recording medium and a driving motor for transferring said reproducing transducer on said rotary recording medium comprises a micro-computer having first and second output ports, where the first output port produces a signal of a pulse form which repeats high-level and low-level periods during a normal-speed transferring mode, and the second output port produces a continuous high-level or low-level signal according to the transferring mode so that a combination of a predetermined level is obtained between the output signal from the first output port, a square wave signal generating circuit applied with the output signal from the first output port of the micro-computer, where the square wave signal generating circuit is triggered to produce a predetermined square wave signal when applied with the signal of a pulse form and not triggered when applied with other signals of constant level, and a switching circuit applied with the output signal from the first and second output ports of the micro-computer, to switch over a plurality of input terminals according to the levels of the applied signals and pass the input terminal voltage through to an output side as an output voltage. The switching circuit supplies the output voltage thus obtained to the driving motor.

BACKGROUND OF THE INVENTION 
The present invention generally relates to transfer control devices for 
reproducing transducers in rotary recording medium reproducing 
apparatuses, and more particularly to a transfer control device capable of 
switching over to perform a high-speed transfer, an intermediate-speed 
transfer, and a normal-speed transfer of the reproducing transducer, by 
use of a small number of output ports of a micro-computer. 
Systems have been realized in which a recording system forms pits in 
accordance with information signal being recorded along a spiral track on 
a flat rotary recording medium (hereinafter referred to as disc), without 
forming a groove therein, and a reproducing stylus traces over along this 
track to reproduce the recorded information signal in response to 
variations in the electrostatic capacitance in a reproducing system. 
In this system, since no groove is provided on the disc for guiding the 
reproducing stylus, pilot or reference signals are recorded on or in the 
vicinity of a track of the information signal, such as a video signal, on 
the disc. Upon reproduction, the reference signals are reproduced together 
with the video signal. Tracking servo control is carried out so that the 
reproducing stylus accurately traces along the track in response to the 
reproduced reference signals. 
In the above described system, since the disc surface is flat having no 
grooves for guiding the reproducing stylus, the reproducing stylus can be 
transferred in a rapid manner towards the radial direction of the disc 
unto a predetermined position without whatsoever damaging the reproducing 
stylus or the disc. That is, a so-called random access operation and the 
like can be performed in the above system. In the random access operation, 
the reproducing transducer is initially transferred at a high speed, then 
the transferring speed is switched over to an intermediate speed when the 
reproducing transducer reaches a position in the vicinity of an intended 
position, and the transfer of the reproducing transducer is finally 
stopped when the reproducing transducer reaches the intended position. The 
above random access operation is performed while addresses on the disc are 
detected. Moreover, during normal reproduction, the reproducing transducer 
is transferred at a normal speed. Accordingly, as a transferring speed for 
the reproducing transducer, there are the following three kinds of speeds. 
(1) Normal transferring speed 
(2) Intermediate speed: 250 times the normal transferring speed, for 
example. 
(3) High speed: 1200 times the normal transferring speed, for example. 
Furthermore, the normal transferring speed is used for a normal reproducing 
mode through a 65-times speed reproducing mode. During normal reproducing 
mode, the reproducing transducer performs reproduction in terms of one 
track. In addition, during 65-times speed reproducing mode, for example, 
the reproducing stylus is successively kicked to an adjacent track at 64 
positions for one revolution of the disc. During the above modes in which 
the reproducing transducer is transferred in a normal manner, a feed pulse 
is supplied to a feed motor every 32 tracks of the disc (every 32 
revolutions of the disc during normal reproducing mode, and every 16 
revolutions of the disc during 2-times speed reproducing mode, for 
example), regardless of multiple speed reproducing mode, to transfer the 
reproducing transducer. 
A control signal is obtained from a micro-computer according to the mode of 
the transferring speed of the reproducing transducer, and supplied to a 
feed motor drive control circuit to perform a rotational speed control 
operation with respect to the feed motor. 
However, various kinds of control signals were conventionally used to 
perform the above speed control operation. Therefore, a plurality of 
output ports of the micro-computer were used for producing the various 
control signals. 
SUMMARY OF THE INVENTION 
Accordingly, it is a general object of the present invention to provide a 
novel and useful transfer control device for a reproducing transducer in a 
rotary recording medium reproducing apparatus, in which the above 
described problems have been overcome. 
Another and more specific object of the present invention is to provide a 
transfer control device for a reproducing transducer in a rotary recording 
medium reproducing apparatus, capable of performing a control operation to 
control each of the above described transferring speed modes of the 
reproducing transducer by use of control signals, wherein the control 
signals are constructed so that only two output ports of a micro-computer 
are required. 
Other objects and further features of the present invention will be 
apparent from the following detailed description when read in conjunction 
with the accompanying drawings.

DETAILED DESCRIPTION 
In FIG. 1, a disc 10 is placed on a turntable 11, and clamped by a clamper 
12. The disc 10 is rotated at a rotational speed of 900 rpm, for example. 
Further, groove guards 10b and 10c are respectively provided at an 
outermost peripheral edge part and an innermost peripheral part of the 
disc 10, so that a recorded region 10a of the disc 10 does not make 
contact with the turntable 11. An information signal such as a video 
signal and an audio signal and reference signals for tracking control, are 
recorded in the recorded region 10a of the disc 10. 
A reproducing transducer 13 comprises a pickup device including a 
cantilever 15 provided with a reproducing stylus 14, a resonator (not 
shown), and the like, and is mounted to a carriage 16. The carriage 16 has 
flange parts provided unitarily at both sides thereof, and the flanges 
have freely rotatable rollers 17a, 17b, and 17c. The roller 17a rolls over 
a rail 19a provided on a chassis 18 of the reproducing apparatus, and the 
rollers 17b and 17c respectively roll over a rail 19b. Accordingly, the 
carriage 16 moves in the direction of an arrow X. 
A belt or a wire 21 is provided across pulleys 20a and 20b. A projection 22 
of the carriage 16 is fixedly provided at a part of the wire 21. The 
rotation of a motor 23 is transmitted to the pulley 20a through a rotation 
transmitting mechanism 24 including a worm and a worm gear. Accordingly, 
the pulley 20a rotates as the motor 23 rotates, and the wire 21 is 
accordingly transferred towards the direction of the arrow X. Hence, the 
carriage 16 is also transferred towards the direction of the arrow X. 
Upon normal reproduction, tracking control is performed with respect to the 
reproducing stylus 14 of the reproducing transducer 13 by a tracking 
control signal formed from reproduced reference signals, so that the 
reproducing stylus 14 always scan over the tracks. 
Description will now be given with respect to an embodiment of a device for 
controlling the transferring speed of the reproducing transducer 13 by 
controlling the rotational speed of the motor 23 according to the 
operational mode of the reproducing apparatus, by referring to FIG. 2. 
First, during a normal transferring speed mode, a pulse signal al is 
produced from an output port 30a of a micro-computer 30. The above pulse 
signal al is produced at the rate of once every 32 tracks of the disc 10, 
where the pulse signal al becomes of high (H) level from a low (L) level, 
as shown in FIG. 3(A). The pulse signal al is supplied to a terminal 2 
of a monostable multivibrator 31 and a terminal 10 of an analog switch 
circuit 32. Moreover, a H-level signal b1 shown in FIG. 3(B) is obtained 
from an output port 30b of the micro-computer 30, and applied to a 
terminal 9 of the analog switching circuit 32. 
The above monostable multivibrator 31 is triggered by a falling edge of the 
signal a1 which is applied to the terminal 2 of the monostable 
multivibrator 31. Hence, a signal c1 shown in FIG. 3(C) is obtained 
through a terminal 3 of the monostable multivibrator 31. In either cases 
where the signal level at the terminals 10 and 9 of the analog 
switching circuit 32 are of L-level and H-level, and H-level and H-level, 
the output obtained from the terminal 3 of the monostable multivibrator 
31 is passed as it is through an output terminal 3 of the analog 
switching circuit 32. 
The signal obtained through the output terminal 3 of the analog switching 
circuit 32 which has a waveform identical to the waveform shown in FIG. 
3(C), is supplied to the motor 23 through amplifiers 33 and 34. 
Accordingly, the motor 23 is rotated every time the reproducing stylus 14 
scans 32 tracks, to transfer the reproducing transducer 13 at a normal 
speed. 
A direct current component of the tracking error signal obtained for 
performing tracking control with respect to the reproducing stylus 14, is 
applied to a terminal 36. Hence, during the normal transferring mode, the 
reproducing transducer 13 is transferred by the motor 23 in a manner such 
that the reproducing stylus 14 and the cantilever 15 are displaced about a 
neutral position of the cantilever 15. The above direct current component 
is applied to a terminal 5 of the monostable multivibrator 31 through 
amplifiers 40 and 41. 
Next, during a stop mode, a L-level signal a2 and a H-level signal b2 shown 
in FIGS. 4(A) and 4(B) are respectively produced from the output ports 30a 
and 30b of the micro-computer 30. 
Since the signal a2 applied to the terminal 2 of the monostable 
multivibrator 31 is a L-level signal, the monostable multivibrator 31 is 
not triggered. Thus, the output obtained from the terminal 3 of the 
monostable multivibrator 31 remains at L-level as shown in FIG. 4(C). 
Moreover, because the signal levels at the terminals 10 and 9 of the 
analog switching circuit 32 respectively are of L-level and H-level, a 
L-level signal c2 obtained from the terminal 3 of the monostable 
multivibrator 31 is passes as it is through the analog switching circuit 
32. Therefore, no voltage becomes applied to the motor 23 to stop the 
rotation of the motor 23, and the stop mode is accordingly obtained. 
Next, during a high-speed transferring mode, L-level signals a3 and b3 
shown in FIGS. 5(A) and 5(B) are respectively produced from the output 
ports 30a and 30b of the micro-computer 30. The monostable multivibrator 
31 is not triggered in this mode, and the signal level at the terminal 3 
of the monostable multivibrator 31 remains at L-level. 
The analog switching circuit 32 passes the voltage applied to a terminal 1 
through the terminal 3 , since the signal levels at the terminals 10 
and 9 are respectively of L-levels. A voltage V is applied to a terminal 
35, and a voltage V1 shown in FIG. 5(C) is applied to the terminal 1 
through a resistor R1. Accordingly, a signal c3 having the voltage V1 
which is shown in FIG. 5(C), is obtained from the terminal 3 of the 
analog switching circuit 32, and then applied to the motor 23 through the 
amplifiers 33 and 34. Therefore, the motor 23 is rotated at a high speed, 
and the reproducing transducer 13 is transferred at a high transferring 
speed. 
On the other hand, during an intermediate-speed transferring mode, a 
H-level signal a4 and a L-level signal b4 shown in FIGS. 6(A) and 6(B) are 
respectively produced from the output ports 30a and 30b of the 
micro-computer 30. The monostable multivibrator 31 is not triggered, and 
the signal level at the output terminal 3 remains at L-level. 
Because the signal levels at the terminals 10 and 9 of the analog 
switching circuit 32 are respectively of H-level and L-level, the voltage 
obtained at the terminal 5 is passed through the terminal 3 . A voltage 
V2 shown in FIG. 6(C) is applied to the terminal 5 of the analog 
switching circuit 32 through resistors R1 and R2. Accordingly, a signal c4 
shown in FIG. 6(C) is obtained from the terminal 3 of the above analog 
switching circuit 32 and supplied to the motor 23. Therefore, the motor 23 
is rotated at an intermediate speed, and the reproducing transducer 13 is 
accordingly transferred at an intermediate transferring speed. 
According to whether the direction towards which the reproducing transducer 
13 is transferred, that is towards a forward direction or a backward 
direction, a switching signal is applied to switching circuits 38 and 39 
from a direction switching circuit 37, to switch over the polarity. Hence, 
the motor 23 is rotated towards the forward direction during a forward 
mode, and rotated towards a backward direction during a backward mode. 
Further, the present invention is not limited to these embodiments, but 
various variations and modifications may be made without departing from 
the scope of the invention.