JPH0430649Y2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Field of Industrial Application The present invention relates to a pick-up return circuit for a high-quality video disc player that optically reproduces a disc record at a constant linear velocity.

(b) Prior Art Compact disc players and optical video disc players require focus control when playing back disc records. However, the retraction range of focus control is narrow and it is necessary to detect the retraction range and bring the objective lens to the retraction range. One way to perform focus control by bringing the objective lens into the focus control pull-in range is to vibrate the objective lens at low speed and with large amplitude in the initial state of focus control, and then perform focus control at the timing of reproduction output generation. How to get started is prized. Regarding this structure, for example, see No. 73 of the July 1981 issue of the magazine "Electronics" published by Ohmsha.
As shown on pages 75-75.

(c) Problems to be Solved by the Invention The focus control pull-in operation of the conventional device described above is always performed with the pickup set at the playback start position in order to quickly start playback.

However, when the above-described focus control pull-in operation is applied to a high-quality video disc player that plays back a video disc record at a constant linear velocity, the video disc record must be rotated at a speed of 50 revolutions per second or more ( Since the compact disc must be rotated at a speed of 8 times per second, and the video disc surface vibrates violently, it is not easy to reliably detect the focus control pull-in range, and even if it is detected, the focus control operation will start. There is a high possibility that the objective lens will be out of the retraction range by the time you do this.

(d) Means to solve the problem The present invention is characterized in that a pickup motor drive control means is provided for positioning the pickup on the outer circumferential side of the playback start position before the start of the video disc record is completed, and returning the pickup to the playback start position when a playback signal is generated.

(E) Effect Therefore, according to the present invention, the pull-in operation under focus control is performed at a low rotational speed position, and after the pull-in is completed, the pick-up returns to the playback start point while under focus control.

(F) Embodiment The present invention will be described below with reference to an embodiment that can be illustrated. In this embodiment, the pickup is moved to a position with a radius of 100 mm (retraction detection position) at the end of playback.
At the start of playback, the pull-in range of focus control is detected and focus control operation is started, and then the pickup is returned to the playback start position with a radius of 70 mm while performing focus control.

The circuit operation of this embodiment will be explained below.
In this embodiment, as shown in FIG. 1, a pick-up motor 1 slides a pick-up 2 along a guide shaft 3 in the radial direction of a video disc record 4 while reproducing FM/MUSE signals. The pick-up 2 uses a focus control coil 2a to displace an objective lens 2b in the optical axis direction, a tracking coil 2c to displace the objective lens 2b in a direction parallel to the guide shaft 3, and focus control is performed using a light receiving element 2d.
A well-known configuration is adopted in which a change in the shape of the zero-order light irradiation spot is detected by the four-part sensor, and the tracking control detects the received light output level of the ±1st-order light.

Therefore, when a stop operation is performed during the playback mode, the rotation of the disk motor is stopped, and all operations related to playback of the pickup 2 are stopped. In this embodiment, the pickup is moved to the retraction detection position in conjunction with this stop operation. Therefore, as shown in FIG. 2, the drive control circuit 5 inputs the position detection output obtained from the pickup position detection means (not shown) to the determination circuit 5a, and gates the instruction output according to the direction in which the pickup should move. This gate circuit is input to the pickup motor drive circuit 6 when a stop signal is generated. Therefore, the pick-up motor 1 moves the pick-up 2 to the retraction detection position by rotating forward or reverse. When the pickup 1 moves to the retracted detection position, the first microswitch 7 is activated and inputs the first detection output P ₁ to the drive control circuit 5. This first detection output _P1 closes the gate circuit 5b,
The rotation of the pick-up motor is stopped. In this state, when the E-Execution operation is performed, the lid of the video disc player is opened and the disc record is replaced.

In this embodiment, when a play operation is performed, the disc motor is activated, and the operation control circuit 8, which inputs the play signal, activates the forced drive circuit 9 when the activation of the disc motor is almost completed. This forced drive circuit 9 applies a large amplitude forced drive voltage of several Hz to the focus control coil 2b. Therefore, the objective lens 2a moves over a wide range including the focus control pull-in range. A reproduction signal is derived from a reproduction signal generation circuit 10 in which a reproduction signal is derived by adding together the four-divided sensor outputs when the objective lens 2a reaches the focus control pull-in range. When the pull-in detection circuit 11 detects a reproduction signal of a certain level or higher, it generates a pull-in detection output L. This pull-in detection output L switches the changeover switch 12, and the focus control voltage derived by the focus control circuit 13 is input to the focus control coil 2b instead of the forced drive voltage, so that the focus control pull-in is switched. Realized. Further, the pull-in detection output L is input to the operation control circuit 5, and the forced drive voltage is turned off. Furthermore, the retraction detection output L is also input to the drive control circuit 5. The return command circuit 5c in the drive control circuit 5 receives the retraction detection output L and issues a reverse rotation command signal.
The pick-up motor 1 is rotated in reverse.
By reversing the pick-up motor 1, when the pick-up 2 reaches a predetermined playback start position, the second
The micro switch 14 operates and the second detection output
Emit P ₂ . When this second detection output _P2 is input to the return command circuit 5c, the movement of the pickup 2 is completed. Note that focus control is performed even during the pick-up return period, and together with the tracking control circuit 15 which operates at the same time as the return is completed, it is possible to reproduce the FM/MUSE signal recorded on the recording track.

In the embodiment described above, the pickup was moved to the retraction detection position during the stop operation, but it goes without saying that it may be moved during the playback operation. Furthermore, it is possible to partially replace the hardware circuit of this embodiment with software, and it goes without saying that the present invention includes such a configuration. Furthermore, the “pickup motor drive control means” in the scope of the utility model registration claim
corresponds to the drive control circuit 5 and the pickup motor drive circuit 6 in this embodiment.

(G) Effect of the invention Therefore, according to the invention, since the retraction range of focus control is detected at the retraction detection position where the rotational angular velocity is lower than the playback start end, reliable retraction is possible, and the effect is great. .

[Brief explanation of the drawing]

FIG. 1 is a circuit block diagram showing an embodiment of the present invention, and FIG. 2 is a circuit block diagram of the main part thereof. 2a...Objective lens, 2...Pickup, 1
...Pick-up motor, 4...Video disc record, 9...Forced drive circuit, 11...Retraction detection circuit, 12...Selector switch, 13...Focus control circuit, 5...Drive control circuit, 6...Pick-up Motor drive circuit.

Claims (1)

[Scope of Claim for Utility Model Registration] A pick-up for optically reproducing a video disc record that records broadband video information and forms a recording track with a constant linear velocity in a spiral shape from the inner circumferential side; a forced drive means for applying a forced drive voltage to the objective lens drive means to displace the objective lens at low speed and with large amplitude; A high-quality video disk comprising: retraction detection means for detecting movement of the retraction detection means; and switching means for supplying a focus control voltage to the objective lens driving means in place of the forced drive voltage upon generation of an output from the retraction detection means. In the player, a pick-up motor drive control means for positioning the pick-up at an outer circumference from the playback start position at least before the start-up of the video disc record is completed, and returning the pick-up to the playback start position upon generation of an output from the detection means. A pick-up return circuit characterized by providing: