JPH0690806B2 - Optical recording / reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to an optical method for recording (writing) information on an information recording medium such as an optical card and reproducing (reading) recorded information by an optical method. In particular, the present invention relates to a two-light source optical recording / reproducing apparatus in which a laser diode is used as a light source for recording information and a light emitting diode is used as a light source for reproducing recorded information. Regarding

<Prior Art> A conventional device of this type is, for example, as shown in FIG. 2 (details will be described later), a first light projecting system using a laser diode 1 as a light source.
A ₁ generates a _first spot light SP ₁ for information recording on the information recording medium 4, and a second light projecting system A ₂ using the light emitting diode 2 as a light source immediately after the generation position of the spot light SP ₁ Is configured to generate a _second spot light SP ₂ for reproducing recorded information.

In this example of the device, a hole-shaped information unit called a "pit" (blackened portion 5 in FIG. 3) is recorded with the first spot light SP ₁ , and then the pit 5 is recorded.
By generating the second spot SP ₂ on the upper side and receiving the reflected light by the light receiving system B including the photodiode 3 and the like,
The presence or absence of the pit 5 and the length thereof are detected so that the record information of the information recording medium 4 can be reproduced in the same manner as the recording.

The size of the length of these pits 5 corresponds to any one of binary data of "1" and "0", and the information recording medium 4 is moved at a constant speed, and a laser is used for a time length corresponding to the data content. By driving the diode 1 and irradiating it with light, a pit 5 having a length corresponding to the binary data is generated.

<Problems to be Solved by the Invention> In the above optical recording / reproducing apparatus, since the optical output of the laser diode 1 greatly changes depending on the temperature, even if the laser diode 1 is driven for a predetermined time length, The size of the pits 5 varies widely, and it is difficult to obtain the pits 5 having a predetermined shape and size.

When the pit shape changes, the light receiving signal by the light receiving system B also changes when the recorded information is reproduced, and there is a problem that the recorded information is erroneously reproduced.

Also, in order to keep the optical output of the laser diode 1 constant, APC
An (Autmatic Power Control) circuit is generally used, but when the laser diode 1 is pulse-driven like this device, it is impossible to use this kind of circuit.

In view of the above-mentioned circumstances, the present invention is a novel method in which the recorded information can be accurately reproduced by correcting the fluctuation of the optical output of the laser diode due to the temperature change or the like to enable the generation of the pit having the predetermined shape and size. An object is to provide an optical recording / reproducing device.

<Means for Solving the Problems> The structure of the present invention for achieving the above object will be described with reference to FIGS. 1 and 2 corresponding to the embodiments. In the optical recording / reproducing apparatus of the present invention, A _first light projecting system A ₁ having a laser diode 1 as a light source for generating a _first spot light SP ₁ for recording information on the information recording medium 4, and reproducing information recorded on the information recording medium 4. A _second light projecting system A ₂ using a light emitting diode 2 as a light source for generating the second spot light SP ₂ immediately after the generation position of the _first spot light SP ₁ .
A light receiving system B for receiving the reflected or transmitted light of the second spot SP ₂ from the information recording medium 4 to reproduce the recorded information on the information recording medium 4, and the laser diode 1 based on the light receiving signal from the light receiving system B. And a correction circuit 6 for correcting the optical output of.

The correction circuit 6 includes a deviation calculation circuit section 7 that compares the received light intensity of the received light signal with a preset reference value to obtain the deviation, and adds the deviation to the output signal to the laser diode 1. The correction drive circuit unit 8 for correcting the optical output of the laser diode 1 is provided.

<Operation> When the optical output of the laser diode 1 fluctuates due to a temperature change or the like, the shape of the pit 5 recorded on the information recording medium 4 with the _first spot light SP ₁ also fluctuates.

A second spot SP ₂ is generated on the pit 5 by the light emitting diode 2. When the reflected or transmitted light is received by the light receiving system B, the deviation calculation circuit section 7 of the correction circuit 6 receives the light reception signal. Of the received light intensity is compared with a preset reference value to determine the deviation, and the deviation is added to the output signal to the laser diode 1 by the correction drive circuit section 8.

As a result, when the optical output of the laser diode 1 changes in the increasing direction, the optical output decreases, and when the optical output of the laser diode 1 changes in the decreasing direction, the optical output increases. Laser diode 1
The output signal to the laser diode 1 is corrected, and the optical output of the laser diode 1 is kept constant even with a temperature change.

<Embodiment> FIG. 2 shows an optical recording / reproducing apparatus of a dual light source system according to an embodiment of the present invention.

The apparatus of the illustrated example has a first information recording medium 4 on the information recording medium 4.
A _first projection system A ₁ for generating a spot light SP ₁ of
The second light projection system A ₂ for generating the _second spot light SP ₂ for reproducing recorded information on the same information recording medium 4 and the reflected light of the second spot SP ₂ are received from the information recording medium 4. And a light receiving system B for reproducing information recorded on the information recording medium 4.

The first light projecting system A ₁ uses the laser diode 1 as a light source. The output light of the laser diode 1 is formed into parallel light by a collimator lens 9, and this parallel light is converted into a beam splitter 10 and a half beam. After passing through the mirror 11, the objective lens 12 focuses on the information recording medium 4 to generate the _first spot light SP ₁ having a diameter of about 1 μm.

When the first spot light SP ₁ is generated on the information recording medium 4, the “pit” (as shown in FIG. 3) (in the figure,
5) is recorded, and in the illustrated example, the pit 5 has a lower light reflectance than the other parts.

The second light projecting system A ₂ uses the light emitting diode 2 as a light source, forms the output light of the light emitting diode 2 into parallel light by the collimator lens 13, and outputs the parallel light to the first light.
After passing through the beam splitter 10 and the half mirror 11 in the light projecting system A ₁ , the objective lens 12 focuses on the information recording medium 4 to generate the second spot light SP ₂ having a diameter of about several μm. To generate. Since the light source of the light emitting diode 2 is large and the output light thereof is not coherent light, the second spot light SP ₂ has a larger diameter than the first spot light SP ₁ of the laser diode 1.

As shown in FIG. 3, the second spot light SP ₂ is generated immediately after the generation position of the _first spot light SP ₁ on the information recording medium 4, and whether it is located on the pit 5 or not. Since the amount of reflected light differs depending on whether the pit 5 is long or short, the presence or absence of the pit 5 and the data content thereof can be determined.

The light receiving system B is the second spot reflected by the information recording medium 4.
The light reflected by SP ₂ passes through the objective lens 12 and is reflected by the half mirror 11, and then is converged by the condenser lens 14 and received by the photodiode 3. Based on the received light signal, the presence or absence of the pit 5 is detected. The data content is determined, and the optical output of the laser diode 1 is corrected by the correction circuit 6 described later to suppress the fluctuation of the optical output due to the temperature change and the change over time, and keep it constant.

FIG. 3 shows an information recording medium 4 having a plurality of pits 5 recorded therein.
FIG. 2 is an enlarged view of the first spot light SP ₁ and the second spot light SP ₁ generated on the information recording medium 4.
₂ is also shown. In the figure, the information recording medium 4
When is moved to the right, each spot light SP ₁ , SP ₂ is scanned in the direction indicated by the middle arrow, but if the positional relationship between both spot lights SP ₁ , SP ₂ is constant, The pit 5 recorded with the _first spot light SP ₁ can be reproduced by monitoring it with the second spot light SP ₂ after a certain delay time immediately after that.

FIG. 4 shows a state in which the pit 5 is being monitored by the second spot light SP ₂ .

The figure also shows a state in which the size of the second spot light SP ₂ is constant, but the size of the pit 5 is changing due to the temperature change and the secular change of the laser diode 1. There is. Of these, Fig. 4 (2) shows the normal pit shape,
4 (1) shows a small pit shape when the light output of the laser diode 1 becomes weak, and FIG. 4 (3) shows a large pit shape when the light output of the laser diode 1 becomes strong.

In FIG. 5, the horizontal axis shows the position of the pit 5 with respect to the second spot light SP ₂ , and the vertical axis shows the received light intensity of the reflected light due to the second spot light SP _2.
Of the intensity of received light in each of the cases of (1) to (3) of FIG. 4 in which the magnitudes of (1) to (3) in FIG.
(Indicated by (3)).

According to the figure, it is understood that the received light intensity changes according to the size of the pit 5, and also changes according to the position of the pit 5 in the spot light SP ₂ .

FIG. 1 shows an example of the configuration of a circuit for driving the laser diode 1. The laser diode 1 and the information recording medium 4 are shown in FIG.
Reference voltage V ₅ for recording the pit 5 having a predetermined shape on the top
Of the reference voltage generating circuit 15 for generating and supplying the laser diode 1 to the laser diode 1, and the voltage applied to the laser diode 1 based on the light receiving signal from the light receiving system B is adjusted to correct the optical output of the laser diode 1. And a resistor 16 for supplying a current for driving the laser diode 1 with the corrected voltage.

When the data pulse signal a having a pulse width according to the data content is given, the reference voltage generating circuit 15 generates the reference voltage V ₅ for a time length corresponding to the pulse width.

The correction circuit 6 includes a monitor circuit 17 for monitoring the intensity of received light when the pit 5 is located at the center of the second spot SP ₂ , and a voltage V (hereinafter, referred to as “the voltage V” applied to the output of the monitor circuit 17). "Monitor voltage") is a predetermined light receiving reference value
A correction drive circuit including a deviation calculation circuit unit 7 including a comparator for obtaining the deviation ΔV by comparing with V _0, and an adder for adding or subtracting the deviation ΔV to the reference voltage Vs to adjust the voltage applied to the laser diode 1. The circuit unit 8 is included.

The light receiving reference value V ₀ corresponds to the monitor voltage for the pit 5 at the normal time shown in FIG. 4 (2),
It is set for each data of "1" and "0", and therefore the deviation ΔV is the proper pit 5 shown in FIG. 4 (2).
Is zero, and the small pit 5 shown in FIG. 4 (1) has a positive value, and the large pit 5 shown in FIG. 4 (3) has a negative value.

The monitor circuit 17 includes a data discriminating circuit 18, a trigger generating circuit 19, a delay circuit 20, a light receiving and amplifying circuit 21, a sample and hold circuit 22 and the like.

The data discriminating circuit 18 is a circuit for discriminating the data content by inputting the data pulse signal a, and a trigger generating circuit.
Reference numeral 19 is a circuit for generating a hold command to the sample hold circuit 22 in response to the detection of data, and a delay circuit 20.
Is a circuit for delaying the hold command by the time until the pit 5 is located at the center of the second spot SP ₂ . Further, the light receiving / amplifying circuit 21 is a circuit for amplifying the light receiving signal of the photodiode 3, and the sample / hold circuit 22 is a circuit for holding the amplified output of the light receiving / amplifying circuit 21 by the hold command.

Therefore, the sample signal held by the sample-hold circuit 22 is pit 5 at the center of the _second spot light SP _2.
Is the amplified output signal at the time when is located.

This sample signal corresponds to the monitor voltage V, and the deviation calculation circuit section 7 obtains the deviation ΔV between the monitor voltage V and a predetermined light receiving reference value V _0, and the correction drive circuit section 8 further determines the deviation ΔV. Is added to the output voltage to the laser diode 1.

However, due to changes in temperature and aging, laser diode 1
When the optical output of 1 decreases, the pits 5 recorded on the information recording medium 4 by the first spot light SP ₁ have a small shape as shown in FIG. 3 (1). In this case, the monitor voltage V output from the sample hold circuit 22 is the light receiving reference value.
A value larger than V ₀ (see the characteristic (1) in FIG. 5) is taken, and the deviation ΔV calculated by the deviation calculation circuit unit 7 becomes a positive value.
Therefore, the correction drive circuit unit 8 adds the deviation ΔV to the reference voltage Vs and outputs the reference voltage Vs, and the output voltage to the laser diode 1 increases and the light output is increased.

On the other hand, when the light output of the laser diode 1 increases due to temperature change or the like, the pits 5 recorded on the information recording medium 4 by the first spot light SP ₁ become large in shape as shown in FIG. 3 (3). . In this case, the sample hold circuit 22
The monitor voltage V output by is smaller than the light receiving reference value V ₀ (see the characteristic (3) in FIG. 5), and the deviation ΔV calculated by the deviation calculating circuit unit 7 is a negative value. Therefore, the correction drive circuit unit 8 subtracts the deviation ΔV from the reference voltage Vs and outputs the subtracted deviation ΔV, the output voltage to the laser diode 1 is reduced, and the optical output is suppressed to a low level.

<Effects of the Invention> Since the present invention is configured as described above, even if the optical output of the laser diode fluctuates due to temperature changes and the like, it is possible to correct this and generate pits of a prescribed shape and size. There is a remarkable effect that the object of the invention is achieved, such that the recorded information on the information recording medium can be accurately reproduced.

[Brief description of drawings]

FIG. 1 is a circuit block diagram of an optical recording / reproducing apparatus according to an embodiment of the present invention, FIG. 2 is an explanatory diagram showing its optical system, and FIG. 3 is an enlarged view showing a format example of recorded information.
FIG. 4 is an explanatory diagram showing variations in pit shape, and FIG. 5 is an explanatory diagram showing received light intensity characteristics for each pit shape. 1 ... Laser diode 2 ... Light emitting diode 6 ... Correction circuit 7 ... Deviation calculation circuit unit 8 ... Correction drive circuit unit A ₁ ...... First light projection system A ₂ ...... Second light projection system B ...... Light receiving system

Claims (3)

[Claims] 1. A first light projecting system using a laser diode as a light source for generating a first spot light for recording information on an information recording medium, and a second projection system for reproducing recorded information on the information recording medium. Second projection system using a light emitting diode as a light source for generating the spot light of the second spot immediately after the generation position of the first spot light, and receiving reflected or transmitted light of the second spot from the information recording medium. It comprises a light receiving system for reproducing the recorded information on the information recording medium, and a correction circuit for correcting the light output of the laser diode based on the light receiving signal from the light receiving system. A deviation calculation circuit unit that compares the intensity with a preset reference value to obtain the deviation, and a correction drive circuit unit that corrects the optical output of the laser diode by adding this deviation to the output signal to the laser diode. An optical recording / reproducing device provided. 2. The first and second light projecting systems each include a collimator lens for collimating the output light of the laser diode and the output light of the light emitting diode, and the light passing through each collimator lens is a common beam splitter, The optical recording / reproducing apparatus according to claim 1, wherein the half mirror and the objective lens are sequentially passed to focus the light on the information recording medium. 3. The optical recording / reproducing apparatus according to claim 1, wherein the light receiving system uses a photodiode as a light receiving element.