KR980011187A - How to detect start and end of video tape - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method for detecting the start and end portions of a video tape, and in order to accurately detect the start and end portions of the video tape using the difference in thickness of the video tape, A method comprising: a first step of detecting a change amount of rotation of a reel from a video tape currently being driven; A second step of sequentially detecting the number of pulses outputted from the capstan motor frequency generator during one rotation of the reel; And a third step of stopping the video tape when the change amount of the number of output pulses detected in the second step shows a value larger than the reference change amount.

Description

How to detect start and end of video tape

In general, the video tape recorder is provided with a detection means for detecting the beginning and end portions of the video tape. This is because when the user selects the function to transport the video tape at a high speed, the high-speed transfer function is not stopped even though the video tape that has been transported at a high speed reaches the start or end portion. To prevent a problem that the tape may be cut or stretched and thus the video tape may be damaged.

As shown in FIG. 1, the sensing means includes a light emitting element 2 protruding from a predetermined position of the deck 1 and capable of receiving an optical signal (light) emitted from the light emitting element 2 (Usually called "start and end sensors") 3 and 4 on the left and right sides of the deck 1, respectively.

In addition, as shown in FIG. 2, a video tape of a home video system (VHS) standard has an opaque magnetized area coated with a magnetic material so as to record various information, And is divided at the end into a transparent lead area having a predetermined length (approximately 2 meters).

In a conventional video tape recorder having such a configuration, the process of detecting the start and end portions of the tape is as follows.

When the video tape travels, the pair of light receiving elements 3 and 4 detect different signals in accordance with the magnetized area and the lead area of the video tape, respectively. That is, when the video tape is positioned in the magnetization area, the optical signal output from the light emitting element 2 is blocked by the video tape and is not transmitted to the light receiving elements 3 and 4. As a result, the light receiving elements 3 and 4 are turned off to output the running control signal of the video tape to the control means for controlling the traveling state of the video tape. Therefore, the video tape runs normally.

On the other hand, when the video tape is positioned in the lead area, the optical signal output from the light emitting element 2 passes through the transparent lead area of the video tape and is transmitted to the light receiving elements 3 and 4. Due to this, the light receiving elements 3 and 4 are turned on to output the stop control signal of the video tape to the control means. Therefore, the video tape is stopped.

However, since the conventional method for detecting start and end portions of a video tape has to include one light emitting element and at least two light receiving elements, the manufacturing cost of the product is increased.

Since the light emitting element described above is mounted on the substantially central portion of the deck and the light receiving element is mounted on the side surface of the deck using a separate printed circuit board, This complicates the complexity, which results in a problem that the working efficiency is lowered.

Further, in order to prevent the light receiving element from malfunctioning due to external light, it must be housed in a separate case. Therefore, in order to mount such a separate case in the deck, a separate clearance space is required, There is a problem that it is difficult to do.

As a result, it is necessary to remove the light emitting element and the light receiving element in order to solve the problem as described above, and it is very important to accurately detect the start and end portions of the video tape in a state where the light emitting element and the light receiving element are removed.

A method of detecting the start and end portions of a video tape recorder from which a light emitting element and a light receiving element are removed is described in detail in the following application filed by the present applicant.

(1) Patent Application No. 92-26344 (92.12.28), Title of the invention: Method for detecting the start and end portions of a tape

(2) Patent Application No. 94-20803 (Apr. 29, 2003), title of the invention: Tape drive control device and method

(3) Patent Application No. 94-20806 (Apr. 24, 2003), title of the invention:

(4) Patent Application No. 95-5141 (Apr. 03, 2003), Title of the invention: Method of judging the tape end of a video tape recorder and a device suitable therefor

As described above, the method of detecting the start and end portions of a conventional video tape using a neural network is as follows.

(PS, PT) obtained by converting the number of revolutions of the capstan motor into frequency during one rotation of a supply reel and a take-up reel mounted on a conventional VHS video tape recorder, (PS2 + PT2 = PC2) is always the same. Therefore, each PS2 and PT2 are detected and learned by the neural network algorithm. Thus, the size of the hub is determined. A detailed description thereof is described in detail in Japanese Patent Application No. 96-15477 (1996.05.10) filed by the present applicant (a method of determining the hub size of a video tape).

On the other hand, as the videotape is transferred, the rotational speed of the reel fluctuates. For example, in forward running, the rotational speed of the supply reel gradually increases with the running of the video tape. Therefore, by detecting the rotation speed of the reel, it is possible to detect the start and end portions of the tape.

Although the rotation speed of the supply reel gradually increases with the progress of the video tape as a whole, in detail, the rotation speed of the reel fluctuates by the pulse operation at each moment. Therefore, by sampling the instantaneous value of the rotational speed of the reel periodically and inputting a plurality of sampling values to the neural network algorithm, it is possible to more accurately detect the start and end portions of the video tape according to the hub size determined in the above- do.

As described above, according to the conventional method of detecting start and end portions of a video tape using a neural network algorithm, by detecting the start and end portions of a video tape according to a plurality of sampling values, There is a corresponding error within approximately 10 laps between the start and end portions and the actual start and end portions. Therefore, there is a problem that the effect of the original purpose of detecting the start and end portions of the video tape is insufficient.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and it is an object of the present invention to provide a method and apparatus for detecting the start and end of a video tape, And an end portion detection method.

1 is a schematic structural view of a typical video tape recorder;

2 is a schematic structural view of a video tape of a typical VHS standard;

3 is a schematic block diagram of a video tape recorder for performing a method of detecting the start and end portions of a video tape according to the present invention.

4 is a flowchart of the operation of the microcomputer shown in FIG.

More particularly, the present invention relates to a video tape recorder in which a start and an end sensor are removed. In the video tape recorder, a neural network algorithm and a thickness difference of a tape are used to detect the start and end portions of a video tape. And a method for detecting the start and end portions of a video tape in which an end portion is detected.

According to an aspect of the present invention, there is provided a method of detecting start and end portions of a video tape, the method comprising: a first step of detecting a change amount of a rotation of a reel from a video tape currently being driven; A second step of sequentially detecting the number of pulses outputted from the capstan motor frequency generator during one rotation of the reel; And a third step of stopping the video tape when the amount of change in the number of output pulses detected in the second step is greater than the reference change amount.

In a fourth aspect of the present invention, the fourth step of determining whether the number of output pulses detected in the second process indicates a value less than or equal to the reference pulse number after the second process is performed, It is preferable to perform the third process only when the number of output pulses indicates a value equal to or smaller than the reference pulse number.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of a method for detecting a start and end portions of a video tape according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 3 shows a schematic block diagram of a video tape recorder according to the present invention.

3, a capstan motor 5 for driving a video tape at a constant speed in a predetermined direction, a capstan motor frequency generator (hereinafter referred to as 'CFG') 5 for generating a pulse signal according to the rotation state of the capstan motor 5, A servo system 7 for controlling the driving state of various components in a deck (not shown) such as a capstan motor 5 and a supply reel and a reel reel, A reel sensing unit 8 for detecting the amount of change in rotation of the microcomputer 9, and a microcomputer 9 for controlling the above components.

The operation of the present invention having the above-described configuration will be described with reference to FIG.

The microcomputer 9 checks whether the video tape is set in the current running state (playback mode, fast forwarding, fast forwarding, fast forward and backward fast searching) through the reel sensing unit 8 (S1). If it is determined in step S1 that the videotape is not in the running state, the microcomputer 9 returns to step S1 to continue checking until the videotape is set in the running state.

If the user inputs a predetermined command for driving the video tape, the microcomputer determines that the video tape is in the running state in the above-described step S1 and drives the servo system 7. Thereby, the capstan motor 5 and the reel are rotated at a predetermined speed. Here, the microcomputer 9 controls the reel sensing unit 8 to detect the amount of change in the rotation of the reel (S2). Here, when the video tape travels in the forward direction, the amount of change in rotation of the supply reel is detected, and when the video tape travels in the reverse direction, the amount of change in rotation of the reel is detected.

Thereafter, the microcomputer 9 checks whether the reel has made one turn by using the amount of change of rotation of the reel detected in the step S2 described above (S3). If it is determined that the reel has not made one turn, ) To repeat the entire process after the step S2.

If it is determined in step S3 that the reel has made one rotation, the microcomputer 9 detects the number of output pulses per revolution of the reel generated from the CFG 6 (S4) Is equal to or smaller than the preset reference pulse number (S5). If it is determined in step S5 that the number of output pulses detected from the CFG 6 is not equal to or less than the reference pulse number, this indicates that the remaining amount of the video tape is equal to or larger than the set value. Therefore, the microcomputer 9 proceeds to step S1 And the entire process after step S1 is repeatedly performed.

If it is determined in step S5 that the number of output pulses detected from the CFG 6 is equal to or smaller than the reference number of pulses, this indicates that the remaining amount of the video tape is almost exhausted. (S6).

Here, in the case of a typical video tape, the thickness of the magnetization region is approximately 20 mu m, and the thickness of the lead region is approximately 40 mu m. Therefore, the reduction ratio of the number of output pulses of the CFG 6 when the video tape is the lead area has a very large value with respect to the reduction ratio of the number of output pulses of the CFG 6 when the video tape is the magnetization region. That is, in the case of the magnetized area, the number of output pulses of the CFG (6) per reel is reduced at a small rate, but in the case of the lead area, the number of output pulses of the CFG (6) It is reduced rapidly. As a result, if it is determined that the number of output pulses detected from the CFG 6 does not decrease sharply in the above-described step S6, this indicates that the magnetized area of the video tape remains on the reel, It is judged that the start and end portions of the CFG 6 have not reached each other, and whether or not the number of output pulses of the CFG 6 suddenly decreases is checked continuously in the above-described step S6.

If it is determined in step S6 that the number of output pulses of the CFG 6 has decreased sharply, this indicates that the magnetized area of the video tape is exhausted and only the lead area exists on the reel. Controls the servo system 7 to stop the video tape (S7), and then ends all the processing. Therefore, the start and end portions of the video tape can be detected more accurately.

As a result, according to the method for detecting the start and end portions of a video tape according to the present invention, at the point where the number of output pulses of the CFG per revolution of the reel sharply decreases by using the thickness difference between the magnetized region and the lead region of the video tape, There is an advantage that the start and end portions of the video tape can be detected more accurately.

Claims (1)

A method for detecting start and end portions of a video tape, the method comprising: a first step of detecting a change amount of rotation of a reel from a video tape currently being driven; A second step of sequentially detecting the number of pulses outputted from the capstan motor frequency generator during one rotation of the reel; And a third step of stopping the video tape when the amount of change in the number of output pulses detected in the second step is greater than the reference change amount. ※ Note: It is disclosed by the contents of the first application.