JPS6220920Y2 - - Google Patents

Description

[Detailed description of the invention] This invention is designed to accurately detect the loop position of a tape drawn into an air column in a magnetic tape position detection device, particularly in a magnetic tape device used as an external storage device for a computer. The present invention relates to a tape position detection device.

Conventionally, this type of optical sensing type tape position detection device has multiple photoelectric conversion elements arranged side by side on the side wall of an air column, and the output of the photoelectric conversion element at a high level position and the output of the photoelectric conversion element at a low level position are detected. The reel motor control circuit is configured to output a position signal for lowering or raising the loop position to the reel motor control circuit. The position signal corresponds to a variable voltage, and by adjusting the bias current and gain of the amplifier at a predetermined loop position in advance, the variable voltage can be set as a voltage value corresponding to the tape loop position that changes thereafter. It is designed to be output from an amplifier.

However, in this conventional configuration, the voltage output fluctuates due to changes in ambient brightness, and as a result, by detecting an erroneous loop position,
This method had the drawback that improper loop position control was performed, and in the worst case scenario, the magnetic tape could fly out from within the air column.

The purpose of this invention is to eliminate the above-mentioned drawbacks of the conventional technology, and in order to achieve this purpose, a photoelectric sensor is provided around the bottom of the air column to detect ambient brightness. According to the output thereof, the output of the photoelectric sensor for detecting the tape loop position is corrected.

Hereinafter, preferred embodiments of this invention will be described in detail with reference to the drawings.

FIG. 1 is a simplified configuration diagram of a magnetic tape device to which an embodiment of this invention is applied, in which numeral 10 denotes a magnetic tape;
1 and 12 are supply and take-up reels, 13 and 14 are reel motors, 15 and 16 are a pair of air columns, 17 is a capstan, 18 is a magnetic head, 19 and 20 are lamps, light receiving elements, and position detection circuits, respectively. and 21 and 22 indicate a light receiving element (for example, CdS) provided at the bottom of the column to detect ambient brightness (external light). FIG. 2 shows the connection relationship between the position detection circuit and the external light receiving element.
The position detection circuit includes an operational amplifier 112 for converting current from a light receiving element for loop position detection, such as a solar cell 111, into voltage, and two variable resistors R1 and R2 for adjusting the bias current and gain of the amplifier 112. It is mainly composed of →.
The variable resistor R1 is such that the tape loop position is
The bias current of the amplifier 112 is adjusted in advance so that the output voltage of the amplifier 112 is zero volts at the center of the column. Also, other variable resistance R
2, the gain of the amplifier is adjusted in advance so that the output voltage of the amplifier changes by 8 volts when the tape loop position changes vertically by several centimeters.

In the position detection circuit pre-adjusted in this way, the amplifier 112 outputs a voltage according to the change in the tape loop position, but since the ambient brightness varies depending on the adjustment time, each adjustment value However, it is not possible to keep the output voltage constant throughout the operating period of the device. This results in erroneous loop position detection as described above. However, according to the feature of this invention, since the CdS 21 and 22 for detecting external light are inserted into the bias current flow path as shown in the second figure, the bias current is corrected according to the surrounding brightness. As a result, the amplifier 112 outputs a constant voltage that does not depend on the amount of external light. In addition, in Fig. 2, _R3 to _R5 are resistors, DZ is a Zener diode, and C1 and C2.
indicate capacitors, respectively.

Although one embodiment of this invention has been described above, the essence of the invention is not limited to this embodiment, and various modifications are possible. For example, the light receiving element 21 for detecting external light may be connected to the output side of the amplifier 112 to correct the output voltage itself.

As is clear from the above explanation, the loop position detecting device of this invention can detect the tape position according to the surrounding brightness, so it is possible to detect tape positions according to the surrounding brightness, so it is possible to detect the tape position according to the surrounding brightness. It is extremely useful when applied to

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a magnetic tape device to which this invention is applied, and FIG. 2 is a specific circuit diagram showing one embodiment of this invention. In the figure, 10 is a magnetic tape, 15 and 1
6 is a pair of air columns, 19 and 20 are tape position detection devices, 21 and 22 are light receiving elements for detecting external light, 111 is a light receiving element for detecting loop position, 1
12 is an operational amplifier, R1 is a variable resistor for bias current adjustment, and R2 is a variable resistor for gain adjustment.

Claims (1)

[Scope of utility model registration request] In a magnetic tape position detection device in which a photoelectric converter is provided on the side wall of an air column to detect the loop position of a magnetic tape drawn into the column, ambient brightness is detected around the bottom of the air column. 1. A magnetic tape position detecting device, characterized in that a detector is provided, and the output of the photoelectric converter is corrected based on the output of the detector.