JP2004319032A - Magnetic recording and reproducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent malfunctions caused by the outer light, etc., without providing a dedicated photodetector and without making a housing transparent, or the like and to start the loading immediately after a tape is inserted when there is no influence of outer light. <P>SOLUTION: When the difference between the collector output of a photo transistor 1 when a LED 25 is off and the collector output of the photo transistor when the LED is on is smaller than a first threshold 6 and when both the collector output of the photo transistor when the LED is off and the collector output of the photo transistor when the LED is on are smaller than a second threshold 7, a CPU 2 determines that the LED 25 for detecting the light transmissive leader tape provided at the start edge and the end edge of a magnetic tape and the photo transistor 1 are affected by the outer light to stop the operation of the magnetic recording and reproducing device (step S5, S6 and S7). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a magnetic recording / reproducing apparatus that detects a light-transmissive leader tape section provided at the start and end of a magnetic tape by a light-emitting element and a light-receiving element and stops tape running, and in particular, prevents malfunction due to external light. The present invention relates to a magnetic recording / reproducing apparatus capable of performing the above-mentioned operations.
[0002]
[Prior art]
2. Description of the Related Art In a magnetic recording / reproducing apparatus that records and reproduces a video signal and an audio signal using a tape cassette containing a magnetic tape (hereinafter sometimes simply referred to as a tape), a front loading type cassette mounting apparatus is often used. When a front loading type cassette mounting device is used, it is widely practiced to provide a flap so that foreign matter does not enter from an insertion portion of the cassette. Some devices such as a camera-integrated VTR use such a front loading type cassette mounting device.
[0003]
Since the front loading type flap does not completely seal the cassette insertion slot but has a gap, external light may enter through the gap to erroneously detect the light transmissive tape end. In particular, a camera-integrated VTR is often used outdoors, and if it is exposed to strong direct sunlight in the summer, etc., erroneous detection often occurs. However, recording may not be possible.
[0004]
For this purpose, a protective cover is provided outside the flap of the cassette mounting device, that is, outside the cassette insertion slot. FIG. 4 shows an example of a camera-integrated VTR equipped with a front loading type cassette mounting device. Reference numeral 41 denotes a cassette insertion portion, and reference numeral 42 denotes a protective cover. FIG. 4 shows a state in which the protective cover 42 is open. In such a VTR, the user once opens the protective cover 42, discharges the cassette, and inserts a new cassette. The operation is completed by closing the protective cover 42 after inserting the cassette. Since the state in which the protective cover 42 is open is susceptible to external light, a switch (not shown) is provided to detect the opening and closing of the protective cover 42, and that the protective cover 42 is closed even when the cassette is mounted. The method of stopping the VTR until the time is detected is adopted. As a conventional example of this kind, Patent Document 1 below discloses a method of making a housing transparent in order to prevent a malfunction due to external light or the like.
[0005]
[Patent Document 1]
JP 2001-111404 A (FIG. 1, abstract)
[0006]
[Problems to be solved by the invention]
However, in the conventional method shown in FIG. 4, recording cannot be started only by mounting the cassette, and recording is started only after the protective cover 42 is closed. Therefore, it takes a long time to start recording even when there is no influence of external light, and there is a problem that a moment at which recording is desired is missed.
[0007]
In addition, if a new sensor is provided to detect external light, it is difficult to detect the effect of external light under the same conditions as the light-receiving element, and accurate detection cannot be performed. There was a problem that it also took. Further, in Patent Literature 1, costs are increased by making the housing transparent to prevent malfunction due to external light or the like.
[0008]
The present invention has been made in view of such a problem, and it is possible to prevent malfunction due to external light without providing a dedicated light receiving element or making the housing transparent or the like. It is an object of the present invention to provide a magnetic recording / reproducing apparatus that can start loading immediately after inserting a tape when there is no tape.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the present invention determines the presence or absence of external light by using a light emitting element and a light receiving element for detecting a light transmissive leader tape section provided at the beginning and end of a magnetic tape. It was done.
That is, according to the present invention, a light-emitting element and a light-receiving element for detecting an opaque magnetic tape portion and a light-transmissive leader tape portion provided at the beginning and end of the magnetic tape portion,
Determines the presence or absence of external light based on the amount of light received by the light receiving element when the light emitting element is off and the amount of light received by the light receiving element when the light emitting element is on, and operates when the external light is detected. Control means for stopping the
A magnetic recording / reproducing apparatus having the same is provided.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram showing an embodiment of the magnetic recording / reproducing apparatus of the present invention, FIG. 2 is a schematic configuration diagram of a tape end detecting device of the magnetic recording / reproducing apparatus of FIG. 1, and FIG. 3 is a flowchart for explaining the operation of FIG. In describing FIG. 1, reference numerals in FIGS. 2 and 3 may be referred to.
[0011]
First, an example of a tape end detecting device using an optical sensor of a VTR will be described with reference to FIG. When the cassette 21 shown in FIG. 2 is mounted on the apparatus, the front cover 22 is released and the tape 28 wound around the reel 23 is pulled out of the cassette 21 and runs in the direction of the arrow. At the beginning and end of the tape 28, a transparent leader tape is used instead of an opaque magnetic tape. Reference numeral 23 in FIG. 2 indicates a supply-side reel. A light emitting element (LED) 25 is provided on the device side, and is arranged so as to fit into a hole 24 provided at the center of the cassette 21 when the cassette 21 is mounted. A light receiving element 1 is also provided on the device side.
[0012]
The detection light 8 emitted from the light emitting element 25 passes through the cassette 21 and reaches the light receiving element 1. However, when the tape 28 is not at the start end or the end, the light emitted from the light emitting element 25 is magnetic. The light is blocked by the tape 28, and a sufficient amount of light does not reach the light receiving element 1. At the start and end of the tape, light emitted from the light emitting element 25 passes through the transparent tape and reaches the light receiving element 1. Even when the cassette 21 is not mounted, the light emitted from the light emitting element 25 reaches the light receiving element 1.
[0013]
FIG. 1 shows an example of a circuit diagram in which a phototransistor is used for the light receiving element 1, the emitter of the phototransistor 1 is grounded, and the collector voltage is taken into the CPU 2. When the magnetic tape 28 blocks the detection light 8 without being affected by external light, the light does not hit the phototransistor 1 irrespective of whether the LED as the light emitting element 25 is turned on or off. Output voltage is high.
[0014]
On the other hand, when the tape 28 is at the start end or end without being affected by external light, when the LED 25 is turned on, the detection light 8 hits the phototransistor 1 and a current flows through the phototransistor 1. Although the output voltage is reduced, when the LED 25 is turned off, no light is applied to the phototransistor 1 and the collector output voltage is increased.
[0015]
However, when external light is incident, the external light is applied to the phototransistor 1 regardless of whether the LED 25 is turned on or off, so that a current flows through the phototransistor 1 and a voltage drop occurs at the resistor R, so that the output voltage is reduced. Is lower. The output voltage is converted into a digital signal by the A / D converter 3 and input to the CPU 2.
[0016]
The operation of the magnetic recording / reproducing apparatus of the present invention will be described based on the flowchart of FIG. First, when the cassette 21 is not mounted, the protective cover 42 (see FIG. 4) is opened, and when the cassette 21 is inserted, the cassette 21 is mounted on the VTR, and the mounting of the cassette is detected by a VTR sensor (not shown) (step S1). ). When it is detected, first, while the LED 25 of the tape end detecting device is turned off, the amount of received light is measured from the collector output (storage 1) of the phototransistor 1 and stored in the storage area 4 inside the CPU 2 (step S2).
[0017]
Next, the LED 25 is turned on (step S3), the output (storage 2) of the phototransistor 1 is measured, and stored in the storage area 5 inside the CPU 2 (step S4). Then, it is determined whether or not the difference between the storage 1 in the storage area 4 and the storage 2 in the storage area 5 is smaller than a first threshold value 6 preset in the CPU 2 (step S5). Is "no external light" and "transparent leader tape", so this external light detection ends.
[0018]
On the other hand, if the difference between the storage 1 in the storage area 4 and the storage 2 in the storage area 5 is smaller than the first threshold value 6 in step S5, it is "with external light" or "opaque magnetic tape portion". Therefore, the process proceeds to step S6, where each value of the storage 1 of the storage area 4 and the storage 2 of the storage area 5 is compared with the second threshold value 7 (step S6). If both the storage 1 of the storage area 4 and the storage 2 of the storage area 5 are not smaller than the second threshold value 7, the detection of the external light is terminated because it is an "opaque magnetic tape part".
[0019]
On the other hand, when both the storage 1 of the storage area 4 and the storage 2 of the storage area 5 are smaller than the second threshold value 7, it is determined that "external light exists", and it is determined that there is an influence of external light. The operation of the magnetic recording / reproducing device is stopped (step S7). Then, the external light detection is completed, and the process returns to step S1. Thus, it is possible to determine whether or not external light is incident on the light receiving element 1 without providing a special external light detection sensor. If there is an influence of external light, the operation of the VTR is stopped. It is possible to protect the VTR and immediately operate the VTR when there is no influence from external light.
[0020]
The external light detection may be performed not only when the cassette 21 is mounted but also continuously during the operation of the VTR. The present invention is not limited to the above-described embodiment, and can be variously modified without departing from the gist of the present invention.
[0021]
【The invention's effect】
As described in detail above, since the presence or absence of external light is determined based on the output voltage of the light receiving element when the light emitting element is turned on and the output voltage of the light receiving element when the light emitting element is turned off, a dedicated light receiving element may be provided, Malfunction due to external light or the like can be prevented without making the housing transparent, and when there is no influence from external light, loading can be started immediately after inserting a tape. Further, when there is an influence of external light, it is possible to provide a magnetic recording / reproducing apparatus which stops the operation of the magnetic recording / reproducing apparatus and does not damage the tape.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing an embodiment of a magnetic recording / reproducing apparatus according to the present invention.
FIG. 2 is a schematic configuration diagram of a tape end detecting device of the magnetic recording / reproducing device of FIG.
FIG. 3 is a flowchart for explaining the operation of the magnetic recording / reproducing apparatus of the present invention.
FIG. 4 is an external view showing a conventional example.
[Explanation of symbols]
1. Light receiving element (phototransistor)
2 CPU
3 A / D converters 4, 5 Storage area 6 First threshold 7 Second threshold 8 Detection light 21 Cassette 22 Front cover 23 Reel 24 Hole 25 Light emitting element (LED)
28 Magnetic tape (tape)
42 Protective cover

Claims (2)

A light-emitting element and a light-receiving element for detecting an opaque magnetic tape portion and a light-transmissive leader tape portion provided at the beginning and end of the magnetic tape portion,
Determines the presence or absence of external light based on the amount of light received by the light receiving element when the light emitting element is off and the amount of light received by the light receiving element when the light emitting element is on, and operates when the external light is detected. Control means for stopping the
Magnetic recording and reproducing apparatus. The control unit compares the first threshold value with the difference between the amount of light received by the light receiving element when the light emitting element is turned off and the amount of light received by the light receiving element when the light emitting element is turned on. The light receiving amount of the light receiving element when the light emitting element is turned off, and both the light receiving amount of the light receiving element when the light emitting element is turned on are compared with a second threshold value, based on the two comparison results. The magnetic recording / reproducing apparatus according to claim 1, wherein the presence or absence of the external light is determined.

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