JPS62217433A - Optical disk reproducing device - Google Patents

Abstract

PURPOSE:To hold the amplitude of a reproducing signal, etc., constant against the variance of a light source, etc., by controlling the quantity of light of a light emission part according to the specular surface reflection level of a reproducing signal and the difference voltage based on a reference voltage. CONSTITUTION:A light quantity control circuit 8 detects the amplitude level (specular surface reflection level) of a signal reproduced by an optical pickup light reception part 4 and outputs the difference voltage based on the reference voltage to control the quantity of light of the light emission part 5 which controls a driving circuit 7 for the pickup light emission part 5 with the output of the control circuit 8. For the purpose, the quantity of light of the light emis sion part 5 is so controlled that the specular surface reflection level is equal to the reference voltage; and the amplitude level of the reproducing signal is controlled to a control value for a disk which is different in reflection factor and modulation degree. Even if the light source has variation in characteristics, the amplitude of the reproducing signal, etc., is held constant.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an optical disc playback device, and more particularly to an optical disc playback device.

Suitable for keeping the specular reflection level of the reproduced signal constant.

This invention relates to a light amount control circuit.

[Conventional technology] Control circuit for the light emitting part of an optical disc playback device.

Regarding the prior art, see Japanese Patent Application Laid-Open No. 59-152532.

It has been reported in the report. In the above publication,

The voltage signal detected by the light receiving section is converted into an average DC voltage by a DC voltage conversion circuit, and the difference voltage is extracted by a comparison circuit which extracts the difference component between this average plane current voltage and a reference voltage. The amount of light output from the emitter/source part is controlled by the differential voltage, and the light emitting part is controlled so that the average DC voltage of the signal detected by the light receiver is equal to the reference voltage. ! 1. [Problems to be Solved by the Invention] The above-mentioned prior art did not take into account the following points.

Figure 2 shows the playback signal of the optical disc, where P is the playback signal level when the light is reflected on the mirror surface of the Dinuk, and the modulation depth is T7. , P(1-7?L) is the pitch of the disc.

This is the level of the reproduced signal when light hits the top surface. .

For this reproduced signal, the average voltage Va = p (1) =
'(constant) 10
becomes. That is, the mirror surface reflection level of the reproduced signal changes depending on the degree of modulation of the Dinuk. This is because the mirror surface level further fluctuates due to variations in the modulation degree due to the disc, which are multiplied by variations in the focus error detection signal, track error detection signal, and RF multiplied signal.

As a result, the variation in the number becomes even larger than the variation due to the ta degree. To explain the RF signal in detail using Fig. 2, for the modulation degree m and the
The AC amplitude when the modulation degree is m'(rn'< trL) is.

be. On the other hand, the mirror surface level P' is 10 such that p'=p.
When controlled as follows, the amplitude ratio is -. Therefore, when the average level of the reproduced signal is controlled to be constant, the amplitude decrease of the RF signal when a disc with a low modulation degree is reproduced is
The problem is that the RF multiplied signal SIN ratio is degraded by 1-1, which is worse than the decrease simply due to variations in modulation degree.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems. Even if the modulation degree varies from disk to disk, the amplitude of the RF multiplied signal will not vary more than the modulation degree variation, and the characteristics of the light source will not vary. Or, if the parts of the optical system 21...6. change due to aging etc. (2), the output voltage of the light receiving section such as the track error detection signal, focus error detection signal, RF' signal, etc. can be kept constant.

[Means for Solving the Problems] The above object is to provide an optical disc reproducing device that uses a light amount control circuit to control the reproduction signal.

Detects the reflection level of the mirror surface and records the reflection level of the mirror surface.

A light amount control circuit that extracts the voltage difference between the voltage and the reference voltage.

The output controls the drive circuit for the light emitting part.

By controlling the amount of light emitted from the light emitting section, the level of light emitted from the playback signal is controlled to be equal to the reference voltage.

This is achieved through control.

[Effect]

The light amount control circuit detects the amplitude level of the signal reproduced from the optical pickup light receiving section (mirror surface skin 15 bells) and outputs the difference voltage from the reference voltage6.The output drives the drive circuit of the light emitting section. When the light intensity of the pickup light emitting section is controlled, the light intensity of the light emitting section is controlled so that the mirror surface reflection level of the signal is equal to the reference voltage, and the reflectance and 20 modulation degree are controlled. The playback signal can be mixed even for different discs.

It is possible to control the color surface level to be constant.

Furthermore, even if the characteristics of the light source vary, the amplitude of the reproduced signal etc. can always be kept constant. [Embodiment] An embodiment of the present invention will be explained below with reference to FIG. 1
2 is an optical disk, 2 is an objective lens, 6 is a beam splinter, 4 is a light receiving section, 26 is a current type pressure converter, 5 is a light emitting section, 6 is an optical pickup, 7° is a drive of the light emitting section 5 The light beam irradiated from the armature source section 5 is a beam beam.

Optical through the printer 3 and through the objective lens 2.

It focuses on the formula disk 1 and is reflected by the disk.

After passing through the objective lens 2 in the opposite direction again, the bea.

The light is reflected by the musblitter 3 and enters the light receiving section 4. The light receiving section 4 outputs a current according to the amount of incident light, and the current-voltage converter 26 outputs a voltage according to the input current, which becomes a reproduction signal of the disc recording signal. The output of the current-voltage converter 26 controls the amount of light.

The light amount control circuit 8 detects the reproduction signal 2 (mirror surface reflection level and outputs the difference voltage between the mirror surface reflection level and the reference voltage. The difference voltage is input to the drive circuit 7, The drive circuit 7 controls the light emitting section'yt,
The amount of light is controlled so that the output difference voltage of the light amount control circuit becomes zero. As described above, according to this embodiment, the mirror surface reflection level of the disc reproduction signal is controlled to be constant.

Wear.

Next, another embodiment of the present invention will be explained with reference to FIG.

I will explain. In Figure 6, components with the same numbers as in Figure 1 are shown.
□Element indicates the same component 1-. ．． Further, 9 is a mirror surface reflection level detection circuit, 10 is a differential amplifier that operates around Vb, 11 is a reference voltage generation circuit, and 12 is a laser.

diode” (LD>, 16 is a monitor diode (MD
)2 14 is a constant voltage source VB, 15 is a constant voltage source Vb, 16
1 is a differential amplifier, 17 is a transistor, and R1-R1 is a resistor. .

A signal reproduced by the light receiving section 4 and the current-voltage converter 26.

The mirror surface reflection level is detected by the mirror surface reflection level detection circuit. Now Laser Dio.

- Mirror surface reflection due to the small amount of light emitted from Do 12? (
``The level is the voltage generated by the reference voltage generation circuit 110.''

If the voltage is also smaller, the output of the differential amplifier 10 will have a voltage lower than Vn.

A thick signal is generated and applied to the input of the drive circuit 7.

It will be done. The drive circuit 7 calculates the amount of light emitted from the constant voltage Vb, the sensitivity of the monitor diode 16, and the resistance R0.
Amplification occurs when a voltage greater than VB is input.

The output voltage of the transistor 16 decreases, and the voltage of the transistor 17 decreases.

A current flows through the transistor 17 due to the drop in the potential.

increases, and the current flowing through the laser diode 12 increases.

As a result, the amount of light emitted increases, and the mirror surface reflection 16 level of the signal becomes equal to the voltage generated by the reference voltage generation circuit 110.

control so that Also, the mirror surface is exposed.

Conversely, when the voltage generated by the reference voltage generation circuit 110 becomes higher than the voltage generated by the reference voltage generation circuit 110, the laser diode 120 emits light.

By reducing the amount, the mirror surface reflection level completely controls the reference l-voltage generating circuit 11. As described above, according to this embodiment, when the laser diode 12 is used as a light emitting section, the mirror surface reflection level of the reproduced signal can be controlled to be equal to the reference voltage.

, 7.

Next, still another embodiment of the present invention will be described using FIG. 4. FIG. 4 shows a specific example of a mirror surface reflection level detection circuit of the light amount control circuit of the present invention.

This is what is shown. In Figure 4, 18 is a transistor, 19 is a resistor, 20 is a capacitor, 21 is a resistor, 22-
is a transistor, 26 is an input to the detection circuit, and 24 is an output. When a reproduced signal is inputted from the input 26.

When the input voltage is higher than the potential of the capacitor 20 by more than f1, a current is injected into the converter 20 through the transistor 18, and the potential of the capacitor 20 becomes higher than the potential of the capacitor 20.
゛rise. Next, the input voltage is the potential of the capacitor 20.

If the voltage is not higher than Vf+, the charge on the capacitor 20 is gradually discharged through the resistor 19. Therefore, for the frequency of input signal 26, capacitor 20 and.

If the time constant of the discharge circuit consisting of resistor 19 is sufficiently long, IJ
By doing so, the mirror surface reflection level of the signal 26 can be detected. In addition, the actual mirror surface reflection level of the transistor 22 and the resistor 21 is shifted lower by the transistor 18, which results in a control error in the present invention. (...
8. This is a level shift circuit that prevents as much as possible, and shifts the voltage of the capacitor 20 so that it becomes higher by Vh.

Next, Figure 5. Another embodiment of the present invention will be described using FIG. In FIG. 5, components having the same numbers as those in FIG. 6 indicate the same components.

Further, 25 is a switch. Further, FIG. 6 shows the timing of light amount control. In FIG. 6, at the moment when the power of the optical disc player is turned on, the level of the reproduced signal is unstable because the laser source irradiated from the pickup to the Dinuku is not focused on the disc. During this unstable period T, when the scene control according to the present invention is performed and the signal amplitude is small, the amount of light emitted from the laser diode 1'' is increased, assuming that the amount of light emitted from the laser diode is small. Actually on disk.

Decreased signal amplitude due to lack of focus.

Because of this, the laser diode is unusually thick.

It may emit light with a certain amount of light and cause destruction. Therefore, immediately after the power is turned on, the switch 25 is set to the B side, the 2-reference voltage is input to the mirror surface reflection level detection circuit, the output of the differential amplifier 10 is set to Vm, and the laser diode is detected using only the constant voltage of 16V. , and then, after the mirror surface reflection level reaches a nearly constant value, turn switch 25 to A'm.
K1. to control the light amount. This also applies when the optical disk reproducing device changes from a stopped state to a reproducing state even if the power is on.

As described above, according to this embodiment, there is an effect that safe light amount control can be performed without the possibility of destroying the laser diode in a transient state such as when the power is turned on or when transitioning from a stop state to a reproducing state.

Ru.

〔Effect of the invention〕

As described above, according to the present invention, even if the modulation degree varies by 11 between discs, the tee can be adjusted more than the modulation degree variation.

Discs can be played back without variations in the amplitude of the playback signal, etc., and even if there are variations in the light source or optical system.

This has the effect of keeping the amplitude of signals etc. constant. 20

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention, and FIG. 2 is a diagram. 6 is a block diagram of another embodiment of the present invention, FIG. 4 is a block diagram of yet another embodiment of the present invention, and FIG. 5 is a block diagram of another embodiment of the present invention. FIG. 6 is a diagram showing the timing of light amount control. 8... Light amount control circuit, 9... Mirror surface level detection circuit, 10... Differential amplifier, 11... Reference voltage generation circuit, 1°25... Switch. I selfishness 1 evil 20th (f)') J3Pa#r9 <2>'l
;zuJ, n4+3rd mouth

Claims (1)

[Scope of Claims] 1. Signals recorded on an optical disc on which a signal is recorded by an optical pickup equipped with a light emitting part and a light receiving part tracking the recording signal track of the disc. In an optical disk reproducing device that reproduces a signal, a voltage difference between the specular reflection level of the signal reproduced by the light receiving section and a reference voltage is generated, and the driving circuit of the light emitting section is controlled by the differential voltage. 1. An optical disc playback device comprising a light amount control circuit that controls the amount of light output from a light emitting section. 2. An optical disk reproducing apparatus according to claim 1, wherein the light amount control circuit is constituted by an amplitude detection circuit for a reproduction signal, a reference voltage generation circuit, and a differential amplifier. 3. In claim 1, the light amount control circuit includes an amplitude detection circuit, a reference voltage generation circuit, a differential amplifier, and the detection circuit input is a signal regenerated by the light receiving section, or 1. An optical disc playback device comprising a switch circuit that switches between using the reference voltage and the reference voltage.