JP2698280B2 - Servo reference setting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a servo reference setting device, and more particularly, to a servo reference setting device used for, for example, a VTR using a software servo.

[0002]

2. Description of the Related Art Conventionally, a drum servo and a capstan servo are performed by a microcomputer for software servo. The drum rotation speed of the drum servo and the capstan rotation speed of the capstan servo, that is, the tape speed, are controlled by the oscillation of the microcomputer. It was determined by the child's frequency. Conventionally, since extremely high accuracy is required to set the above-described drum rotation speed and tape speed to regular values,
Only a crystal oscillator (accuracy ± 0.01%) was used as the oscillator.

[0003]

However, the crystal oscillator has a problem in that the cost of the crystal oscillator is higher than that of a ceramic oscillator, an RC oscillator, an LC oscillator, or the like, so that the device itself becomes expensive. . Therefore, a main object of the present invention is to form a servo circuit at low cost.
The object is to provide a servo reference setting device.

[0004]

According to the present invention, there is provided a servo reference setting device for calculating at least one of a drum servo reference cycle and a capstan servo reference cycle by a microcomputer using an oscillator, which has higher accuracy than the oscillator. The cycle of a synchronization signal generated from a video signal circuit operated by a second oscillator is measured, and at least one of the drum servo reference cycle and the capstan servo reference cycle is corrected based on the measured cycle. A servo reference setting device.

[0005]

In the video signal circuit, a vertical synchronizing signal (Vsync) is created by a crystal oscillator,
The Vsync cycle is determined by the microcomputer (simply
Measurement). Based on the measured values, the drum servo reference cycle and the capstan servo reference cycle calculated by the microcomputer oscillator (for example, a ceramic oscillator) are corrected, and the drum rotation speed and the capstan rotation speed are adjusted to the accuracy of the crystal oscillator. To hold.

[0006]

According to the present invention, it is possible to maintain the drum rotation speed and the capstan rotation speed at the accuracy of the crystal oscillator without using a crystal oscillator as the oscillator of the microcomputer. Servo can be realized at low cost. Further, the power supply of the video signal circuit used in the present invention can be turned off after at least one of the drum servo reference cycle and the capstan servo reference cycle is corrected. The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, a servo reference setting device 10 of this embodiment is built in a camera-integrated VTR, for example. The servo reference setting device 10 includes a microcomputer 12 for servo system control. For the microcomputer 12, for example, a ceramic oscillator 14 having an accuracy of ± 0.5% is used. The microcomputer 12 calculates a drum servo reference cycle and a capstan servo reference cycle based on the oscillation frequency of the ceramic oscillator 14.

A power switch 16 for a VTR circuit (not shown) and a power switch 20 for a camera circuit 18 are connected to the microcomputer 12. When the power switch 16 or 20 is turned on, a signal to be turned on is given from the microcomputer 12 to the camera circuit 18, and the camera circuit 18 is turned on. The microcomputer 12 controls on / off of the power supply of each of the camera circuit 18 and the VTR circuit. In the camera circuit 18, a crystal oscillator 22 having an accuracy of, for example, ± 0.01% is used. The vertical synchronizing signal Vsync created based on the crystal oscillator 22 is used as a drum phase reference in the recording mode. The microcomputer 12 measures the cycle of the vertical synchronizing signal Vsync generated by the camera circuit 18, and corrects the servo reference cycle based on the measured value.

Then, servo signals are supplied from the microcomputer 12 to the drivers 24 and 26, respectively, and the capstan motors 28 and 30 are controlled. The FG signals output from the capstan motor 28 and the drum motor 30 are amplified by the amplifiers 32 and 34, respectively, and then input to the microcomputer 12 as FG pulses.

In the operation of the microcomputer 12, as shown in FIG. 2, it is first determined in step S1 whether or not the power switch 16 or 20 is turned on. If the power switch 16 or 20 has been turned on, step S3
, Both the power supply of the camera circuit 18 and the power supply of the VTR circuit are turned on. In step S5, the camera circuit 1
It is determined whether or not the power supply of the camera circuit 18 has been sufficiently stabilized.
Go to 7. In step S7, the microcomputer 12 measures the cycle T _V of the vertical synchronization signal Vsync generated from the video signal circuit of the camera circuit 18. The period T _V of the vertical synchronizing signal Vsync is created based on the crystal oscillator 22 of the camera circuit 18. That is, the video signal generated by the camera circuit 18
Created on the basis of the pulse frequency × f _SC (sub-carrier), and thus the period T _V of the vertical synchronizing signal Vsync accuracy is equal to the crystal oscillator 22. Therefore, by measuring the cycle T _V of the vertical synchronization signal Vsync and using the measured value, the drum servo reference cycle and the capstan servo reference cycle can be corrected as follows.

First, in step S9, the drum servo reference cycle is corrected according to equation (1) or (2).

[0012]

(Equation 1)

[0013]

(Equation 2)

[0014] Since the sampling frequency of the drum servo is normal to an integer multiple of a vertical synchronization signal Vsync, a may be the the period T _V 1 / n times the value as a reference period. Therefore, in step S9, equation 2
Can also correct the drum servo reference cycle. Then, in step S11, the capstan servo reference cycle is corrected according to Equation 3.

[0015]

(Equation 3)

Next, it is determined in step S13 whether or not the camera is in the camera recording mode. If the camera is in the camera recording mode, initial processing is performed in step S15, and this routine ends. On the other hand, if it is the playback mode instead of the camera recording mode in step S13, that is, if the power switch in step S1 is not the power switch 20 but the power switch 16, the microcomputer 12 should turn off the camera circuit 18. A signal is output and the power supply of the camera circuit 18 is turned off. Then, after performing the initial processing in step S15, this routine ends.

In the above embodiment, the microcomputer 12
Although the ceramic oscillator 14 is used as the oscillator used in the above, the present invention is not limited to this, and an RC oscillator, an LC oscillator, or the like may be used. The signal measured by the microcomputer 12 is not limited to the vertical synchronizing signal Vsync, but may be a composite synchronizing signal. In this case, the servo reference cycle is corrected by the cycle obtained from the composite synchronizing signal.

Further, according to this embodiment, there is no need to add hardware, so that there is almost no increase in cost.
Further, even when the power switch 16 is turned on instead of the power switch 20, the power of the camera circuit 18 is turned on for 1 to 2 seconds. In this case, if the camera image is muted, no adverse effect occurs. .

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a flowchart showing the operation of the embodiment of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Servo reference setting device 12 ... Microcomputer 14 ... Ceramic oscillator 18 ... Camera circuit 22 ... Crystal oscillator 28 ... Capstan motor 30 ... Drum motor

Claims (1)

(57) [Claims] 1. A servo reference setting device for calculating at least one of a drum servo reference cycle and a capstan servo reference cycle by a microcomputer using an oscillator, wherein the servo reference setting device is operated by a second oscillator having higher accuracy than the oscillator. A servo reference setting device, wherein a period of a synchronization signal generated from a video signal circuit is measured, and at least one of the drum servo reference period and the capstan servo reference period is corrected based on the measured period.