JPS61242348A - Optical disk reproducing device - Google Patents

Abstract

PURPOSE:To inform a user that the stains or dew condensation are produced at an optical system by detecting the degree of the stains and the dew condensation of the optical system of an optical pickup and turning on and off a display element according to the results of said detection. CONSTITUTION:A drop-out detecting circuit consists of a peak wave detecting circuit 25, a comparator 26 and a display circuit 27 and detects a peak level VP from an RF signal. This peak wave detection includes a time constant decided by a capacitor C2 and a resistance R2. The comparator 26 compares the level VP obtained by the circuit 25 with the reference voltage V1 given from a variable voltage source E1. The display circuit 27 consists of a switching transistor TRQ1, a light emitting diode LED1, a base resistance R3 and a collector resistance R4 and switches the TRQ1 with the control signal VS1 produced from the comparator 26. Thus the power supply voltage Vcc is applied to the LED1 and the LED1 is turned on for display of the drop-out display.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an optical disc playback device that uses an optical pickup to read information signals from an optical disc, and particularly relates to an optical disc playback device that uses an optical pickup to read information signals from an optical disc. Related to improvements to detect and display dropouts due to etc.

[Technical background of the invention and its problems] Conventionally, optical disc playback devices have mainly been stationary and have not been taken outdoors, but in recent years, the use of ICs and miniaturization has progressed, and compact discs in particular Portable type (hereinafter abbreviated as CD) playback devices have appeared. However, since this CD playback device uses an optical pickup, if this CD playback device is used outdoors in the winter and then brought into a heated room, condensation may form on the optical system such as the objective lens and prism. It will stick.

In this case, since the laser light is diffusely reflected, the DC level of the RF multiplied signal taken out from the optical pickup decreases, and the eye pattern becomes very dirty, making data slicing impossible. A similar phenomenon also occurs when the objective lens becomes dirty with dust or the like. At this time, there may be no sound at all, and there is a risk that the user will think that there is a malfunction.

Therefore, conventional optical disc playback devices have been required to detect and display the degree of dirt on the optical system and the occurrence of dew condensation.

In addition, a portable type video tape recorder (hereinafter referred to as V
(abbreviated as TR) is provided with a dew condensation removal function that detects and displays dew condensation adhering to the head and simultaneously removes the dew condensation. For reference, the configuration of the condensation removal function of the VTR is shown in FIG. 4 and will be briefly described.

First, in this dew condensation removal function, a low frequency pulse L F P is sent from the microcomputer 11 provided in the VTR.
is generated and transmitted through the buffer 1 circuit 12 to a semi-fixed resistor R1 for detecting level adjustment, a resistor R1, a DC cut capacitor CI, and a DEW provided near the VTR head.
dew condensation) is supplied to the attenuator circuit 13 consisting of the sensor S1. Here, if dew condensation occurs on the head, the number of resistance valves of the DEW sensor S1 decreases, so the level of the output pulse of the attenuator circuit 13 decreases. Taking advantage of this, the output pulse of the attenuator circuit 13 is level-compared with the reference voltage in the Schmitt trigger type comparator circuit 14, and if it is lower than the reference voltage, an H (high) level detection signal is generated, and this is sent to the microcontroller circuit 14. It is being input into the computer 11. Although not shown, when the microcomputer 11 receives a detection signal, it activates a heater installed near the head to prevent input operations other than the eject mode, and at the same time prevents loading even if a tape cassette is inserted. It controls the packet up.

[Purpose of the Invention] This invention was made in consideration of the above circumstances, and is intended to notify the user when playback becomes impossible due to dirt or dew condensation in the optical system of an optical pickup. The purpose of the present invention is to provide an optical disc playback device that can perform the following functions.

``Summary of the Invention In other words, the optical disc playback device according to the present invention has the following features:
The degree of adhesion of dirt or condensation on the optical system of the optical pickup is detected by detecting that the output signal of the optical pickup has decreased to a predetermined level or less for more than a predetermined time in a reproduction state, and in this detection state. By controlling the display element to turn on and off based on this information, the user is informed of the presence of dirt or condensation on the optical system.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described in detail with reference to FIGS. 1 to 3.

FIG. 1 shows a configuration in which the present invention is applied to a 3-beam type CD reproducing apparatus, and reference numeral 21 in the figure is a multi-division photodetector of a 3-beam type pickup. Light receiving areas A to D of this photodetector 21 are for the main beam, and E and F are for the sub beam. Among these, the respective outputs of the light receiving areas A and C and B and D are each added with a current, and then converted into a voltage signal by current/voltage conversion circuits 22 and 23. Then, each voltage signal is added by an adder circuit 24, and is supplied as a well-known RF multiplied signal to a data demodulation circuit (not shown). At the same time, the RF multiplied signal is supplied to the dropout detection circuit.

The drop alarm 1~detection circuit includes a peak detection circuit 25,
It is composed of a comparator 26 and a display circuit 27.

The peak detection circuit 25 detects the peak level of the above RF multiplied signal.
It detects P, and capacitor C2 is used for peak detection.
and has a time constant determined by resistor R2. This time constant is set to be sufficiently longer than the time when RF signal dropout may occur due to scratches or vibrations on the disk, and the R signal drop time that occurs during search.
is the peak level VP obtained by the peak detection circuit 25
is compared with a reference voltage V1 from a variable voltage source E1, and when the peak level VP is higher than the reference voltage V1, an L level control signal VSI is generated, and when it is lower than the reference voltage V1, an H level control signal VSI is generated. The display circuit 27 is composed of a switching transistor Q1, a light emitting diode LEDI, a base resistor R3, and a collector resistor R4.
1, the power supply voltage VCC is applied to the light emitting diode LED1, and this light emitting diode L
ED1 is turned on to indicate dropout detection.

That is, when the optical system of the optical pickup is normal, the RF multiplied signal eye pattern is as shown in FIG. 2(a). At this time, the peak detection circuit 25
When the RF multiplied signal peak level VP is detected by the comparator 26 and compared with the reference voltage v1, the peak level v
P is sufficiently higher than the reference voltage v1. Therefore, since the control signal VSI output from the comparator 26 is a torque signal, the transistor Q1 of the display circuit 27 maintains an off state.

Therefore, the light emitting diode LED1 does not light up.

If dirt or condensation adheres to the optical system, the light beam emitted from the pickup and the light reflected from the disk will be diffusely reflected due to the dirt or condensation, so the RF multiplied signal eye pattern will become as shown in Figure 2 (b). As shown, as the level decreases, the detection pattern becomes dirty. Furthermore, when dirt and dew condensation become heavily deposited, the level drops significantly as shown in FIG. 2(C), and the eye pattern becomes even dirtier, making it impossible to read data such as the RF multiplied signal.

Therefore, the reference voltage V1 is set higher than the peak level ■P of the eye pattern shown in FIG. 2(C), and the lowest state in which data can be read from the RF multiplied signal is detected. This is possible if the comparator 26 detects that the output level vP of the peak detection circuit 25 has fallen below the reference voltage v1. At this time, the comparator 26 outputs the control signal vS1
is set to the torque level, the transistor Q1 of the display circuit 27 is turned on, and the light emitting diode LEDI is turned on.

This allows the user to be informed that data such as the RF multiplied signal cannot be read due to dirt or condensation on the optical system.

Therefore, the CD playback device configured as described above can notify the user of the device status even when playback is not possible, and the CD playback device will not be erroneously determined to be malfunctioning.

It is also possible to notify the timing of cleaning the objective lens of the pickup.

FIG. 3 shows another embodiment of the invention. In addition, in FIG. 3, the same parts as in FIG. 1 are denoted by the same reference numerals.
Only the different parts will be described here.

Figure 3 shows an improved CD playback device shown in Figure 1 to determine whether the RF double signal dropout is due to dirt in the optical system.
This makes it possible to identify whether the problem is due to condensation.
The output of the comparator 26 is the first AND gate G1.
The above display circuit (hereinafter referred to as the display circuit of cylinder 1) 2 via
7 and is also supplied to the second display circuit 30 via the second AND gate G2. This second display circuit 30, like the first display circuit 27, includes a switching transistor Q2, a light emitting diode LED2, and a base resistor R.
5 (the collector resistor is shared by the resistor R4 of the first display circuit).

On the other hand, a DEW sensor S2 is provided near the optical system of an optical pickup (not shown). This dew condensation sensor S
2 is incorporated into the dew condensation detection circuit 31.

This dew condensation detection circuit 31 applies voltage v2 from voltage source E2 to DEW sensor S2 via resistors R6 and R7, and the voltage at point a by DEW sensor S2 whose resistance value changes depending on the degree of dew condensation. It detects changes. The voltage VD detected by the dew condensation detection circuit 31 is supplied to a comparator 32 and compared in level with a reference voltage v3 from a variable voltage source E3 that sets a dew condensation detection level. This comparator 32 is trubel when VD > V3, and VD≦■3
This control signal VS2 is supplied to the other input terminal of the first AND gate G1, and is also supplied to the second AND gate G2 via the inverter gate G3. supplied to the other input end.

In other words, in a CD playback device configured as described above, under normal conditions when there is no dirt or condensation on the optical system,
Since the resistance value of the DEW sensor S2 is sufficiently high, the voltage VD at point a is higher than the reference voltage V3. Therefore, the control signal VS2 from the comparator 32 is a trubel. This control signal @VS2 is supplied to the first AND gate G1 and also to the second AND gate G via the inverter gate G3.
2. At this time, the output of the inverter gate G3 is at the H level, but since the control signal vS1 from the comparator 26 is at the L level, the outputs of the first and second AND gates Gl, G2, vG1. Both vG2 and C are at L level. Therefore, the first and second display circuits 27.
30 transistors Ql, G2 are in the off state, and each light emitting diode LEDI.

Both L and ED2 do not emit light.

Next, when only dew condensation occurs in the optical system, the resistance value of the DEW sensor S2 decreases, so the voltage VD at point a decreases and becomes lower than the reference voltage v3.

At this time, the control signal VS2 from the comparator 32 is H
level. On the other hand, the control signal VS1 from the comparator 26 is also at H level. Therefore, the output VGI of the first AND gate G1 becomes H level, the output VG2 of the second AND gate G2 becomes L level, and only the light emitting diode LED1 of the first display circuit 27 lights up.

Further, when no dew condensation occurs but dirt is attached to the optical system, the output VD of the dew condensation detection circuit 31 does not change, so the control signal VS2 from the comparator 32 is at L level. On the other hand, the control signal VSI from the comparator 26 is at H level. Therefore, the output VGI of the first AND gate G1 is at L level, and the output VGI of the first AND gate G2 is at L level.
The output VG2 becomes H level, and only the light emitting diode LED2 of the second display circuit 30 lights up.

In other words, (1) is a normal state, (2) is a state where only condensation occurs, and (3) is a state where only dirt is attached to the optical system.
), the operation of the CD playback device is as shown in the table below.

Therefore, even if the sound is no longer produced, the user can know that condensation has occurred if the first light emitting diode LEDI lights up, and if the second light emitting diode LED2 lights up, the user can know that the optical system is dirty.

As shown by the dotted lines in FIG. 3, the outputs VGI and G2 of the first and second ant gates Gl and G2 are supplied to the speech synthesis circuit 33, and when VGl is at H level, the message "Due to condensation, please wait for a while." When VS2 is at H level, an audio signal saying "Please clean the lens" is generated. Then, by supplying these audio signals to the speaker 35 or the headphones 36 via the amplifier circuit 34 and outputting the audio, it is possible to inform the user of the countermeasure method.

In addition, the following can be considered as other application examples.

(1) By setting the comparator and reference voltage to two or more levels and displaying two or more types, it is possible to inform the user of the degree of condensation and how dirty the lens is.

(2) A dropout meter can be constructed by directly driving the meter with the output of the peak detection circuit. This allows the user to be informed of the degree of dew condensation and the degree of dirt on the lens more accurately. in this case,
If the dropout meter and the music signal level meter are used in common, or if the portable type is used in common with the battery meter, the device will not be bulky and will be good.

[Effects of the Invention; As detailed above, the present invention provides an optical disc that can notify the user if playback becomes impossible due to dirt or condensation in the optical system of the optical pickup. A playback device can be provided.

[Brief explanation of drawings]

FIG. 1 is a block circuit diagram of a CD playback device showing an embodiment of the optical disc playback device according to the present invention, FIG. 2 is a waveform diagram for explaining the operation of the same embodiment, and FIG. 3 is a diagram of the present invention. FIG. 4 is a block circuit diagram showing the configuration of a dew condensation detection mechanism conventionally used in a VTR. 1110. Microcomputer, 12...Amplifier,
13... Condensation detection circuit, 14... Comparison circuit, 21.
...Multi-division photodetector, 22.23...Current-voltage conversion circuit, 24...Addition circuit, 25...Peak detection circuit, 26...Comparator, 27...Display device, 30...Display Device, 31... Condensation detection circuit, 32
...Comparator, 33...Speech synthesis circuit, 34.
...Amplification circuit, 35...Speaker, 36...Headphone. Applicant's agent Patent attorney Takehiko Suzue Figure 4

Claims (1)

[Claims] In an optical disc playback device that uses an optical pickup to play back an information signal from an optical disc on which the information signal is recorded, the output signal of the optical pickup is lowered to a predetermined level or less for a predetermined time or more in a playback state. a state detection circuit that detects the degree of dirt or condensation on the optical system of the optical pickup by detecting the amount of dirt or condensation on the optical system of the optical pickup; and a display circuit that controls turning on and off of the display element based on the detected state of the state detection circuit. An optical disc playback device characterized by comprising: