JPH07302402A - Preamplifier for magnetic regenerator - Google Patents

Abstract

(57) [Abstract] [Purpose] To widen the band of a preamplifier of a magnetic reproducing device for reproducing a signal detected by a magnetic head mounted on a rotating body. [Structure] A liquid crystal shutter 3 which is provided on an upper drum 11 and whose light transmittance is variable according to a detection signal from a magnetic head 1, and an infrared light emitting LED 4 which irradiates light on one surface of the liquid crystal shutter 3. And the chassis 1 facing the upper drum 11
And a photoelectric conversion element 8 which receives light emitted from the other surface of the liquid crystal shutter 3 according to the light transmittance of the liquid crystal shutter 3 and photoelectrically converts the light into electricity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a preamplifier of a magnetic reproducing apparatus, and more particularly to a preamplifier of a magnetic reproducing apparatus for reproducing a signal detected by a magnetic head arranged on a rotating body.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram of an example of a preamplifier of a conventional magnetic reproducing apparatus, and shows a preamplifier of a rotary head helical scan type video tape recorder.

In FIG. 3, 31 is a magnetic head, 32 is a rotary transformer, and 33 is a regenerative amplifier. The primary sides of the magnetic head 31 and the rotary transformer 32 are arranged on a rotary drum (not shown), and the primary sides of the magnetic head 31 and the rotary transformer 32 are connected to each other. On the other hand, the secondary side of the rotary transformer 32 is arranged on a fixed drum (not shown) facing the rotary drum. The secondary side of the rotary transformer 32 is connected to the regenerative amplifier 33.

Therefore, the signal detected by the magnetic head 31 is input to the regenerative amplifier 33 via the rotary transformer 32 and amplified.

FIG. 4 is a block diagram of another example of a preamplifier of a conventional magnetic reproducing apparatus, which shows a preamplifier of a rotary head helical scan type video tape recorder. In the figure, the same components as those in FIG. 3 are designated by the same reference numerals.

In FIG. 4, 31 is a magnetic head, 32 is a rotary transformer, 33 is a regenerative amplifier, and 34 is a preamplifier. A rotary drum (not shown) is provided on the primary side of the magnetic head 31, the preamplifier 34, and the rotary transformer 32.
The magnetic head 31 is connected to the input end of the preamplifier 34, and the output end of the preamplifier 34 is connected to the primary side of the rotary transformer 32. On the other hand, the secondary side of the rotary transformer 32 is arranged on a fixed drum facing the rotary drum. The secondary side of the rotary transformer 32 is connected to the regenerative amplifier 33.

Therefore, the signal detected by the magnetic head 31 is amplified by the preamplifier 34 and then input to the regenerative amplifier 33 via the rotary transformer 32 and further amplified.

[0008]

However, according to the former preamplifier (FIG. 3) of the former magnetic reproducing apparatus, since the output voltage of the magnetic head is as small as several tens of μV, noise is induced in the rotary transformer. There is a problem that the reproduction S / N is lowered and resonance is caused by the inductance of the rotary transformer and the input capacitance of the reproduction amplifier, so that reproduction in a wide band cannot be performed.

According to the former amplifier (FIG. 4) of the former magnetic reproducing apparatus, the signal detected by the magnetic head 1 is amplified by the preamplifier to prevent the reproduction S / N from decreasing. There was a problem that broadband reproduction could not be performed.

Therefore, it is an object of the present invention to provide a preamplifier of a magnetic reproducing apparatus capable of reproducing a wide band.

[0011]

In order to solve the above problems, the present invention has the following configuration.

That is, in the preamplifier of the magnetic reproducing apparatus for reproducing the signal detected by the magnetic head arranged on the rotating body, the preamplifier is provided on the rotating body, and the light transmittance according to the detection signal from the magnetic head. The light transmittance varying means, the light source for irradiating the one surface of the light transmittance varying means with light, and the fixed portion facing the rotating body are provided with the light transmittance of the light transmittance varying means. The photoelectric conversion means for receiving light emitted from the other surface of the light transmittance varying means according to the above, and photoelectrically converting the light to electricity, and an amplifying means for amplifying an output signal from the photoelectric conversion means. And a preamplifier for the magnetic regenerator.

[0013]

According to the present invention having the above-mentioned structure, the light transmittance changing means provided on the rotating member can change the light transmittance according to the detection signal from the magnetic head. The light from the light source is applied to one surface of the light transmittance varying means and emitted from the other surface according to the light transmittance of the light transmittance varying means. The light emitted from the other surface of the light transmittance varying means is incident on the photoelectric conversion means,
It is converted to electricity. That is, the rotating body and the fixed portion are optically coupled, and the detection signal from the magnetic head provided on the rotating body is used as the output electric signal of the photoelectric conversion means arranged in the fixed portion without passing through the rotary transformer. Acts like.

[0014]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention and shows a part of a reproducing system of a video tape recorder.

In FIG. 1, reference numeral 1 is a magnetic head for detecting a signal from a magnetic tape, and the magnetic head 1 is connected to a preamplifier 2. The output end of the preamplifier 2 is connected to the liquid crystal shutter 3 corresponding to the light transmittance varying means.
The liquid crystal shutter 3 has its light transmittance characteristic varied according to the output voltage from the preamplifier 2, and the light transmittance thereof is linearly varied with respect to the output voltage from the preamplifier 2. On one surface of the liquid crystal shutter 3, an infrared emitting LED 4 corresponding to a light source is provided.
Infrared rays are emitted from.

Reference numeral 5 is a rotary transformer, and AC power obtained by amplifying the output of the oscillator e by the power amplifier 6 is supplied to the primary winding of the rotary transformer 5. On the other hand, a rectifier circuit 7 is provided on the secondary winding of the rotary transformer 5.
Are connected. The rectifier circuit 7 rectifies the AC power induced in the secondary winding of the rotary transformer 5 to generate a DC voltage V _CC and supplies it to the preamplifier 2.

By the way, the infrared light transmitted through the liquid crystal shutter 3 enters the photoelectric conversion element 8 corresponding to the photoelectric conversion means. The photoelectric conversion element 8 is, for example, a phototransistor that responds to infrared light to generate and output a current according to the infrared light. The output current of the photoelectric conversion element 8 is output linearly with respect to the incident infrared light. Photoelectric conversion element 8
Output current is amplified by the regenerative amplifier 9.

FIG. 2 is a diagram showing the structure of the drum.

As shown in FIG. 2, the upper drum 11 corresponding to the rotating body driven to rotate by the drum motor 10 includes:
Of the configuration shown in FIG. 1, the magnetic head 1 and the preamplifier 2
, Liquid crystal shutter 3, rectifier circuit 7, and rotary transformer 5
The secondary side of is arranged. Reference numeral 15 is a head output terminal. The motor shaft 12 of the drum motor 10 is hollow inside and has a shape through which infrared light can pass.

The liquid crystal shutter 3 is arranged above the motor shaft 12. An infrared light emitting LED 4 is arranged above the liquid crystal shutter 3. The infrared light emitting LED 4 is only required to be able to irradiate the upper surface of the liquid crystal shutter 3 with infrared light, and may be fixed to the upper drum 11 via a supporting member (not shown) or above the upper drum 11. Means may be provided for fixing to.

Below the upper drum 11, a lower drum 13 which is a fixed portion is arranged. The lower drum 13 is fixed to the chassis 14. On the lower drum 13, the primary side of the rotary transformer 5 is arranged so as to face the secondary side of the rotary transformer 5. Further, the drum motor 10 described above is disposed below the lower drum 13. A motor shaft 12 is fixed to the rotation center of the drum motor 10, and a photoelectric conversion element 8 is arranged below the motor shaft 12.

Although the power amplifier and the regenerative amplifier 9 are not shown in FIG. 2, they are provided inside the lower drum 13 or on a circuit board provided in the chassis 14.

When the upper drum 11 is rotationally driven by the drum motor 10, the liquid crystal shutter 3 is also rotated and the upper surface of the liquid crystal shutter 3 is irradiated with infrared light from the infrared light emitting LED 4. The magnetic head 1 detects a signal from the magnetic tape as the upper drum 11 rotates. As a result, the light transmittance of the liquid crystal shutter 3 changes according to the signal detected by the magnetic head 1.

The infrared light transmitted through the liquid crystal shutter 3 is emitted from the lower surface of the liquid crystal shutter 3, passes through the inside of the motor shaft 12, and enters the photoelectric conversion element 8. Photoelectric conversion element 8
The output current of is amplified by the regenerative amplifier (9). That is, in the reproduction signal system, the rotary transformer is not interposed due to the optical coupling between the rotating body and the fixed portion,
An output electric signal of the photoelectric conversion element 8 is obtained according to the detection signal from the magnetic head 1.

Therefore, even if the output voltage of the magnetic head 1 is as small as several tens of μV, a high S / N can be obtained without being affected by the inductive noise of the rotary transformer, and the inductance of the rotary transformer and the input capacitance of the regenerative amplifier can be obtained. Since resonance does not occur with and, wide band reproduction can be performed.

Although the video tape recorder has been described in this embodiment, the present invention is not limited to this, and the present invention can be applied to other magnetic reproducing apparatus of the rotary head helical scan system, for example, DAT (digital audio tape recorder). It is also conceivable to supply a recording current to the magnetic head via a rotary transformer and apply it to a magnetic recording / reproducing apparatus.

[0027]

As described above, according to the present invention, the rotating body and the fixed portion are optically coupled, and the detection signal from the magnetic head provided on the rotating body does not pass through the rotary transformer.
Since it is an output electric signal of the photoelectric conversion means arranged in the fixed portion, S / S which is not affected by noise from the rotary transformer
It is possible to obtain N good reproduced signals. Further, since there is no resonance between the inductance of the rotary transformer and the input capacitance of the amplifying means, it is possible to obtain a wideband reproduced signal.

[Brief description of drawings]

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

FIG. 2 is a diagram showing a configuration of a drum.

FIG. 3 is a block diagram of an example of a preamplifier of a conventional magnetic reproducing device.

FIG. 4 is a block diagram of another example of the preamplifier of the conventional magnetic reproducing apparatus.

[Explanation of symbols]

 1 Magnetic Head 3 Liquid Crystal Shutter 4 Infrared Light Emitting LED 8 Photoelectric Conversion Element 11 Upper Drum 13 Lower Drum 14 Chassis

Claims (1)

[Claims] 1. A preamplifier of a magnetic reproducing apparatus for reproducing a signal detected by a magnetic head disposed on a rotating body, wherein the preamplifier is provided on the rotating body, and an optical signal is output according to a detection signal from the magnetic head. The light transmittance changing means for changing the light transmittance, the light source for irradiating the one surface of the light transmittance changing means with light, and the light transmittance changing means provided on the fixed portion facing the rotating body. Photoelectric conversion means for receiving light emitted from the other surface of the light transmittance varying means in accordance with the light transmittance of the means and converting the light into electricity, and amplifying means for amplifying an output signal from the photoelectric conversion means. A preamplifier for a magnetic reproducing apparatus, comprising: