JPH02292741A - Device and method for superimposing high frequency - Google Patents

Abstract

PURPOSE:To stably perform a reproducing operation extending over a long period by providing a high frequency oscillation circuit to generate one high frequency signal, and a distributor having plural output terminals to distribute output to plural output setting one high frequency signal as an input signal and to connect the output terminal to an individual selected by plural semiconductor laser elements, respectively. CONSTITUTION:One high frequency oscillation circuit 4 and one distributor 5 to transmit the input signal to the output terminal of same number as that of selected semiconductor laser elements 2a-2n are provided. And the output of the high frequency oscillation circuit 4 is inputted to the distributor, and one output terminal of the distributor is connected to one of the selected semiconductor laser elements 2a-2n individually, respectively, and a system is constituted so as to superimpose and apply the high frequency signal of same frequency on all selected semiconductor laser elements 2a-2n. In such a manner, since no unrequired beat signal to be mixed in a reproduced signal area occurs, a reproduced signal with high quality can be maintained extending over the long period.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Fields] The present invention focuses laser beams emitted by an optical head, particularly a plurality of semiconductor laser elements, onto a storage medium using one objective lens, and stores information in parallel. The present invention relates to a high frequency superimposing device and a high frequency superimposing method in a semiconductor laser drive circuit of a multi-beam optical head that performs recording and reproduction.

[Prior Art] Conventionally, multi-beam optical heads have been known that converge laser beams emitted by multiple semiconductor laser elements onto a storage medium using a single objective lens, and record and reproduce information in parallel. .

Generally, in an optical head using a semiconductor laser, during reproduction, the laser beam mainly reflected on the surface of the storage medium returns to the semiconductor laser, causing interference, causing a problem of return optical noise.

To solve this problem, it has been conventionally practiced to superimpose a high frequency (for example, 5QOMI-t.) signal on the drive current of the semiconductor laser. The same applies to a multi-beam optical head using a multi-beam semiconductor laser, and will be explained below with reference to the drawings.

FIG. 3 is a block diagram for explaining a conventional high-frequency superposition device and high-frequency superposition in a multi-beam semiconductor laser drive circuit, in which 1 is a multi-beam semiconductor laser, 2a, 2b, . . . 2n (hereinafter representative). 2 if you do
) are the individual semiconductor laser elements 3a, 3b, . . . that constitute the multi-beam semiconductor laser l. 3n (hereinafter referred to as 3 if representative) is a semiconductor laser drive circuit that drives each semiconductor laser element 2 individually; 4a, 4b, . . .
. , 4n (hereinafter referred to as 4 if representative) is a high frequency oscillation circuit that individually generates a high frequency signal to be superimposed on each semiconductor laser element. In the above, the configurations of the semiconductor laser element drive circuit 3 and the high frequency oscillation circuit 4 are well known to those skilled in the art, and therefore their explanations will be omitted.

In the conventional example with the above configuration, one semiconductor laser drive circuit 3 and one high frequency oscillation circuit 4 are each individually connected to one semiconductor laser element 2 of the multi-beam semiconductor laser (2), and at the time of reproduction, the reproduction power is A direct current is passed through each semiconductor laser element 2 by each semiconductor laser drive circuit 3 so as to emit a laser beam of . At the same time, a high frequency signal is independently superimposed on the drive current of each semiconductor laser element 2 from each high frequency oscillation circuit 4. As a result, in the conventional example described above, the return optical noise of each semiconductor laser element 2 is suppressed.

[Problems to be Solved by the Invention] However, in the above-mentioned conventional high-frequency superimposition device and high-frequency superposition method in a multi-beam optical head, the number of high-frequency oscillation circuits 4 equal to the number of semiconductor laser elements 2 is provided. As the oscillation frequency of each high-frequency oscillation circuit 4 fluctuates independently, the beat signal between the oscillation frequencies of each high-frequency oscillation circuit 4 becomes the frequency of the reproduction signal band of the recorded information and is mixed into the semiconductor laser drive current. There was a problem. That is, there is a problem in that the beat signal becomes noise and stable reproduction operation cannot be performed over a long period of time.

The present invention was devised to solve the above problems, and aims to stabilize and improve the quality of the reproduced signal over a long period of time when reproducing information from a recording medium using a multi-beam optical head. An object of the present invention is to provide a high-frequency superimposition device and a high-frequency superposition method in a multi-beam semiconductor laser drive circuit and drive method that can perform the following steps.

[Means for Solving the Problems] The configuration of the high frequency superimposing device of the present invention for achieving the above object is to focus beams emitted by a plurality of semiconductor laser elements onto a storage medium using one objective lens and collimate them in parallel. A high-frequency superimposition device in a semiconductor laser drive circuit of a multi-beam optical head that records and reproduces information electronically includes a high-frequency oscillation circuit that generates one high-frequency signal, and a plurality of high-frequency oscillator circuits that distribute the single high-frequency signal to multiple input signals. The present invention is characterized by comprising one distributor having an output terminal and individually connecting the output terminal to each of the selected plurality of semiconductor laser elements.

Furthermore, the configuration of the high frequency superimposition method of the present invention to achieve the above object is to focus beams emitted by a plurality of semiconductor laser elements onto a storage medium using one objective lens, and record and reproduce information in parallel. In the high frequency superposition method in the semiconductor laser driving method of a multi-beam optical head, first one high frequency signal is generated, then the one high frequency signal is distributed to a plurality of signals, and then the distributed high frequency signal is transmitted to the plurality of high frequency signals. The method is characterized in that the voltage is applied to each of the selected semiconductor laser elements individually.

[Operation] The present invention distributes and applies a high-frequency signal to be superimposed on each of a plurality of selected semiconductor laser elements constituting a multi-beam semiconductor laser for the purpose of suppressing return optical noise from a single high-frequency signal. By doing so, high-frequency signals of completely the same frequency are superimposed on each of the semiconductor laser elements, eliminating the generation of beat signals between the respective high-frequency signals, and enabling stable reproduction operation in the multi-beam optical head. Make it.

[Example] Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention,
1 is a multi-beam semiconductor laser, 2a2b,...,2
n (hereinafter referred to as 2 if representative) is the individual semiconductor laser tree, 3a, 3 constituting the multi-beam semiconductor laser.
b,... 3n (hereinafter referred to as 3 in representative cases) is a semiconductor laser drive circuit that is individually connected to each of the semiconductor laser elements 2 and drives each, 4 is a high frequency oscillation circuit that generates one high frequency signal, and 5 is at least It has the same number of output terminals as the number of selected semiconductor laser elements 2, and transmits a high-frequency signal obtained by dividing the above-mentioned one high-frequency signal as an input signal to those output terminals! There are two distributors. In the above, one semiconductor laser drive circuit 3 and one semiconductor laser element 2 of the multi-beam semiconductor laser 1 are each connected individually, and the oscillation output of the high frequency oscillation circuit 4 is connected to the input terminal of the distributor 5, One output terminal of the distributor 5 is individually connected to one semiconductor laser element 2. In this example,
The number of semiconductor laser elements 2 to be selected is the total number of elements, and therefore a high frequency signal is applied and superimposed on all the elements of the semiconductor laser elements 2 constituting the multi-beam semiconductor laser. As the configuration of the high frequency oscillation circuit 4, a well-known configuration can be used as in the conventional case. For example, a delay type oscillation circuit using a delay line or the like is generally used, and an overtone type crystal oscillation circuit or an oscillation circuit using a tunnel diode or the like can also be used.

FIG. 2 is a block diagram showing an example of horizontal construction of the seven-point distributor 5. As shown in FIG. In the figure, 5l is an input terminal to which one high-frequency signal is connected, 52 is a distribution amplifier composed of, for example, one stage of transistors, and 53a, 53b, . The high frequency signals distributed by the output terminals 54a, 54b, . . . This is a buffer amplifier for individually transmitting data to each of the 54n. For example, an emitter follower circuit can be used as the buffer amplifiers Zi53a, 53b, -, 53n. These buffer amplifiers 53a, 53b,..., 53
The output terminals 54a, 54b, -, 54n correspond to the semiconductor laser elements 2a, 2b, . . . in FIG. 1, respectively.
..., 2n, prevents each drive current from flowing to the other.

Next, the present invention will be described as a high frequency superimposition method.

As is clear from the above description, the configuration of one embodiment of the high frequency superimposition method of the present invention is as follows: (1) First, one high frequency signal is generated.

(2) Next, that one high frequency signal is distributed to multiple output systems.

(3) Next, the distributed high-frequency signal is applied to each of the selected semiconductor laser elements (for example, all the elements) of the plurality of semiconductor laser elements constituting the multi-beam semiconductor laser and is individually applied and multiplexed to eliminate the return optical noise. suppress.

It is. Thereby, a high frequency signal having the same frequency is superimposed on each of the selected semiconductor laser elements, thereby preventing the generation of a beat signal during reproduction.

The operation and effect of the embodiment configured as above will be described. In this embodiment, all elements of the multi-beam semiconductor laser I are selected semiconductor laser elements. During reproduction, each semiconductor laser drive circuit 3 causes a direct current to flow through each semiconductor laser element 2 so as to emit a laser beam with reproduction power. At the same time, one high frequency signal generated by the high frequency oscillation circuit 4 is distributed through the distributor 5 and superimposed on the drive current of each semiconductor laser element 2.

This suppresses the return optical noise of each semiconductor laser element 2. In the above, the high-frequency signals superimposed on the drive current of each semiconductor laser element 2 are distributed based on one high-frequency signal, so they have the same frequency and do not mix into the reproduced signal band of recorded information. There is no possibility that a beat signal will occur. Therefore, in a multi-beam optical head using a multi-beam semiconductor laser 1, when the laser beams emitted from each semiconductor laser element 2 are focused on a storage medium and information is reproduced in parallel, the reproduction operation is stabilized. As a result, the reproduced signal quality is stabilized and improved over a long period of time.

Although the above embodiment deals with the multi-beam semiconductor laser 1, a configuration may also be adopted in which a given number of single-beam semiconductor lasers are arranged to obtain a plurality of beams. In this case, since the return optical noise characteristics of each semiconductor laser element 2 may differ, the distributor 5 may have a built-in function for adjusting the amplitude of the high-frequency signal to each output terminal. In addition, although the distributor 5 is configured to supply high-frequency signals to all elements of the multi-beam semiconductor laser 1, the semiconductor laser element 2 (
(including wiring), the high-frequency signal is supplied from the distributor 5 only to a given semiconductor laser element (for example, every other semiconductor laser element), which is less than the total number of elements. It would be nice to have a configuration that does that. As described above, the present invention can be applied in various ways and can take various embodiments in accordance with its gist.

[Effects of the Invention] As is clear from the above description, according to the high frequency superimposition device and the high frequency superposition method of the present invention, one high frequency oscillation circuit and one input signal can be processed in the same number as the number of semiconductor laser elements from which one input signal is selected. the output terminal of the high frequency oscillation circuit is input to the distributor, and one output terminal of the distributor and one of the selected semiconductor laser elements are individually connected to each other. Since a high frequency signal of the same frequency is superimposed and applied to all of the selected semiconductor laser elements, there is an advantage that unnecessary beat signals that mix into the reproduced signal band are not generated.

Therefore, there is an advantage that a high quality reproduced signal can be maintained for a long period of time.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram showing an example of the configuration of a distributor, and FIG. 3 is a block diagram of a conventional example. 1...Multi-beam semiconductor laser, 2a, 2b,...
・, 2n... semiconductor laser element, 3a, 3b,...
3n... Semiconductor laser drive circuit, 4... High frequency oscillation circuit, 5... Distributor. 17 nore 1000 beam half 4-sho lede 2a, 2b, -2n half 4 body racer゜Aoju 3a, 3b,・
-・3n Hanpeng Iki Rape” Rikan word 4 Hatake F8 wave front shooting times 5 distribution number 2 figure 1 figure 3

Claims (2)

[Claims] (1) In a high frequency superimposition device in a semiconductor laser drive circuit of a multi-beam optical head that focuses beams emitted by a plurality of semiconductor laser elements onto a storage medium using a single objective lens and records and reproduces information in parallel, 1 a high-frequency oscillation circuit that generates two high-frequency signals;
and a distributor having a plurality of output terminals for distributing one high-frequency signal as an input signal to a plurality of input signals and individually connecting the output terminals to each of the selected plurality of semiconductor laser elements. High frequency superposition device. (2) In a high frequency superimposition method in a semiconductor laser driving method for a multi-beam optical head in which beams emitted by multiple semiconductor laser elements are focused onto a storage medium using a single objective lens and information is recorded and reproduced in parallel, firstly, It is characterized by generating one high frequency signal, then distributing the one high frequency signal to a plurality of signals, and then applying and superimposing the distributed high frequency signal to each of the selected plurality of semiconductor laser elements individually. High frequency superposition method.