JPH02278530A - Optical disk recording and reproducing device - Google Patents

Abstract

PURPOSE:To detect abnormality with simple constitution only to set a threshold value by using a circuit for focus control for detecting that the level of reflected light is lowered on the surface of an optical disk by the abnormality of an optical system such as the dirt of an objective lens, etc. CONSTITUTION:When a video signal is recorded and reproduced, focus adjustment is executed to a loaded optical disk 1. An objective lens 3c is moved according to the control of a system controller 4. Then, an exact focus position 1b is detected from the prescribed difference signals of four sensors, which constitute a focus detecting sensor 3b, and the objective lens is positioned. At such a time, when there is the dirt in the objective lens, the detecting level of reflected beam l2 is lowered to be less than 70% and is less than the threshold value. Then, although a pulse signal is normally outputted twice in the l2 and l3, the time is made once. In such a case, it is judged that there is the abnormality in the optical system. Then, such a state is displayed on the display screen of a display device 6 by superimpose with being turned on and off.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical disk recording/reproducing apparatus suitable for application to, for example, an apparatus for recording or reproducing video signals.

[Summary of the Invention] The present invention is an optical disc recording/reproducing device that records or reproduces signals using a laser beam, and when performing focus adjustment, detects the level of reflected light of the laser beam on the surface of the optical disc. It is designed to detect abnormalities in the optical system such as dirt on the objective lens and deterioration of the laser source.

[Prior Art] Conventionally, optical disk recording/reproducing apparatuses have been developed that record or reproduce signals such as video signals using laser beams. This type of device has the disadvantage that unless the laser beam from the laser source in the optical block reaches the optical disk with a constant power, it is not possible to record or reproduce signals satisfactorily.

For this reason, in the past, when a laser beam was emitted from a laser source such as a laser diode and irradiated onto an optical disk through an objective lens, the level of the reflected beam from this optical disk was detected by a sensor placed near the laser source. Was. And, what is the power of the laser beam from the laser source so that this detection level remains constant? 1 AJl wholesale.

[Problem to be solved by the invention]

By the way, even if the laser output from the laser source is normal due to the above-mentioned control, if the objective lens placed in the optical path between the laser source and the optical disk is dirty,
Unless this dirt is removed, normal recording and playback may not be possible. In particular, if the lens is dirty when recording a signal, a degraded signal with a worsened signal-to-noise ratio will be recorded, and even if you try to play back this recorded signal after removing the dirt on the lens, it will not be possible to reproduce it well, and the lens will become dirty during playback. The damage was greater than if it were.

Conventional recording/reproducing devices cannot detect this dirt on the objective lens.

In view of the above, it is an object of the present invention to provide an optical disc recording and reproducing apparatus that can easily detect abnormalities in the optical system such as dirt on the lens.

As shown in FIGS. 1 and 2, for example, the optical disc recording/reproducing apparatus of the present invention irradiates a laser beam II from a laser source (3a) onto an optical disc (1) through an objective lens (3c). In an optical disc recording/reproducing device that records or reproduces signals using this irradiation beam, when driving the objective lens (3c) to adjust the focus,
Surface (1a) of optical disk (1) of laser beam l,
The level detector for the reflected beam i2 detects an abnormality in the optical system when the detection level falls below a predetermined level.

[Effect]

According to such a configuration, the surface (1a) of the optical disc (1)
Reflected light I! , z changes in level in direct correlation with an abnormality in the optical system such as dirt on the objective lens (3c), so abnormal conditions can be detected depending on the level of reflected light on this surface (1a) detected during focus adjustment. I can do it.

[Means to solve the problem]

[Embodiment] Hereinafter, an embodiment of the optical disc recording/reproducing apparatus of the present invention will be described with reference to the accompanying drawings.

In FIG. 1, ( ) indicates an optical disk on which signals are recorded. In this example, video signals are recorded on this optical disk (1), and this optical disk (1) is connected to a spindle motor (2). is rotated at a predetermined speed. Then, an optical block (3) containing optical system components is placed close to one side of this optical disk (+). As shown in FIG. 2, this optical block (3) is a laser beam for recording or reproducing signals! , and a detector (not shown) for detecting the return light reflected from the signal recording surface (1b) of the optical disk (1). And the laser source (
The objective lens (3a) is placed between the optical disc (1) and the optical disc (1).
By arranging optical path components such as C) (others not shown),
A laser beam 11 from a laser source (3a) enters the optical disc (1) from the surface (1a) and hits the signal recording surface (1b).
), and during recording, this laser beam 11 forms a predetermined pit on the signal recording surface (1b) according to the recording signal, and during reproduction, this laser beam I! , 1 is detected by a detector, and the recorded signal is read.

In this case, in this example, the objective lens (3c) is driven by a predetermined driving means to generate a laser beam! A focus l sensor (3b) which is movable in the same direction X as the irradiation direction of laser source (3a) and which detects the level of reflected light is disposed close to the laser source (3a). This focus detection sensor (3b
) is actually divided into four parts, and the sum signal of the detection signals of the four sensors is used as the output signal for abnormality detection.

Returning to the explanation of FIG. 1 again, the optical block (3) is irradiated with the laser beam 11 from the laser source (3a).

The position of the objective lens (3c), etc. are controlled by the system controller (4). In addition, the level detector (5) detects the level of the signal output by the focus detection sensor (3b) of the optical block (3) according to the amount of received light, and the detection signal of this level detector (5) is sent to the system controller. (4). In this case, in this example, the level detector (5) detects whether the sum signal for abnormality detection outputted by the focus detection sensor (3c) exceeds a preset darkness value vth, and A pulse signal is supplied to the system controller (4) when it is detected that the value exceeds the threshold value. This threshold value vth
When the optical system of this device is normal, the laser beam from the laser source (3a)! , is set to a level that is approximately 70% of the level of the sum signal for abnormality detection detected when the focus position of , is near the surface (1a) of the optical disc (1).

Based on the level detection data of this reflected light, the system controller (4) controls the position of the objective lens (3c) and adjusts the focus of the laser beam.

Further, in this example, a display device (6) is connected to the system controller (4), and the display bag W (6) is configured to be able to display characters and the like. In this case, the display device (6) is a monitor display device that displays the video to be recorded.

Next, we will explain the operation of recording a video signal on the optical disc (1) or reproducing the recorded video signal using the device of this example. First, when recording and reproducing this signal, Focus adjustment is performed for (1). In this example, this focus adjustment is performed by the objective lens (3) under the control of the system controller (4).
c) Gradually bring the disc closer to the optical disc (1) from the farthest position from the optical disc (1). By doing this, the focus position of the laser beam II emitted from the laser source (3a) is first aligned with the optical disc (1).
This occurs when the surface becomes close to the surface (1a). At this time, the abnormality detection signal outputted by the focus detection sensor (3b) becomes a voltage signal V corresponding to the amount of light of the reflected beam 12 on this surface (1a), as shown in FIG. 3A. When this voltage signal (1) exceeds the threshold value vth, the level detector (5) supplies the system controller (4) with a Luhalus signal P that changes to low level, as shown in FIG. 3B.

Then, attach the objective lens (3c) to the optical disk (1).
By bringing it closer to the optical disk (3a), the focus position of the laser beam β1 emitted from the laser source (3a)
1) near the signal recording surface (1b). At this time, the abnormality detection signal output by the focus detection sensor (3b) is a reflected beam from this position recording surface (1b), as shown in FIG. 3A! The voltage signal becomes 2 depending on the amount of light in step 3. At this time, the voltage signal ■2 is approximately 3 times higher than the voltage signal ■1 mentioned above.
Since the signal becomes twice as high and exceeds the threshold value vth at this time as well, the level detector (5) supplies the system controller (4) with a pulse signal P2 that changes to low level.

Then, the system controller (4) detects when a more accurate focus position is on the signal recording surface (1b) based on the predetermined difference signals of the four sensors that constitute the focus detection sensor (3b), and detects when the focus position is on the signal recording surface (1b). ), fix the position of
Finish focus adjustment.

At this time, if the state of the optical system is normal, two pulse signals P, , Pz are supplied from the level detector (5) to the system controller (4). Here, the signal recording surface (1
b) The level of the reflected beam 13 from the surface (1a) of the optical disk (1) does not change much even if there is dirt on the lens due to the large amount of birefringence.
is directly affected by the state of the optical system and easily changes.For example, when there is relatively large dirt on the objective lens (3c), this reflected beam! The detection level ■ of No. 2 decreases to 70% or less and becomes below the threshold value vth. Therefore, the pulse signal P1 is not output, and the pulse signal P1 is not output until the focus adjustment is completed.
The system controller (4) does not detect the pulse signal P2L twice, and when it detects it only once, the system controller (4) determines that there is an abnormality in the optical system, and the user of this device detects the video signal etc. When an attempt is made to record (or reproduce) on the disk (1), the occurrence of an abnormality is displayed blinking on the display screen of the display device (6) with superimposed letters or the like.

When the user confirms this display, the user stops recording and performs cleaning of the objective lens (3c), etc., so that normal recording can be performed from now on, and a good video signal with a good S/N ratio can be recorded. In addition, various abnormalities in the optical system, such as dirt on the optical path other than the objective lens (3c), dirt on the surface (1a) of the optical disk (1), or deterioration of the laser diode itself that constitutes the laser source (3a), It can be detected by this decrease in detection level (1).

In the above embodiment, the occurrence of an abnormality is simply displayed and the user is responsible for cleaning the objective lens (3C). However, most abnormalities in the optical system that actually occur are caused by the objective lens (3C). Therefore, a cleaning mechanism for the objective lens (3c) consisting of a brush or the like is attached to the recording/playback device, and the system controller (4c) is used to detect abnormalities.
) is detected, the cleaning mechanism may automatically remove the dirt.

Furthermore, it goes without saying that the present invention is not limited to the above-described embodiments, and can take various other configurations without departing from the gist of the present invention.

There are profits to be made.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
FIG. 3 is a configuration diagram of the main part of the example shown, and FIG. 3 is a waveform diagram for explaining the example shown in FIG. (1) is an optical disk, (3a) is a laser source, (3b)
is the focus detection sensor, (3C) is the objective lens, (4
) is the system controller, (5) is the level detector, (
6) is a display device. 〔Effect of the invention〕

Claims (1)

[Scope of Claims] An optical disc recording/reproducing device that irradiates an optical disc with a laser beam from a laser source through an objective lens and records or reproduces a signal using the irradiated beam, comprising: driving the objective lens; When adjusting the focus,
An optical disc recording/reproducing apparatus that detects the level of reflected light of the laser beam on the surface of the optical disc, and detects an abnormality in the optical system when the detected level falls below a predetermined level.