JPH0510277Y2 - - Google Patents

Description

[Detailed description of the invention] Technical field of the invention The invention relates to an optical disk recording and reproducing device,
In particular, the present invention relates to an optical disk recording and reproducing apparatus that can also use different types of optical disks with different reflectances.

Prior Art A recordable and reproducible optical disk device having an optical pickup, a tracking servo device, a focus servo device, a disk drive device, and a signal processing circuit is well known. The laser light supplied to the optical disc during recording is much stronger than the laser light used to read information already recorded on the optical disc.
It goes without saying that such a powerful laser beam should not be supplied to a recordable and reproducible disc during playback, but the reflectance of a read-only disc and a recordable and reproducible disc is quite different, so it is important to avoid using them in the same device. When playing back, the amount of reflected light varied and stable tracking servo and focus servo could not be applied.

For this reason, means have been proposed for automatically determining the type of disk placed in the device. For example, a method has been proposed in which a label indicating the disk type is attached to the disk and the type is determined by reading this label, or a method is applied in which unfocused light is applied to the disk and the type of disk is determined based on the amount of reflected light. There is.

All of these methods require a separate optical system for disk discrimination, and the amount of hardware required for disk discrimination, including the related control circuit and signal processing circuit, is considerable.

Purpose of the invention The purpose of the invention is to make it possible to identify the disc type with a minimum of additional equipment without having to process the optical disc for type identification, and to stabilize each servo gain based on the results. An object of the present invention is to provide an optical disc recording/reproducing device that achieves the following objectives.

Composition of the invention It includes a focus error detection means for outputting a focus error signal of the laser light irradiated onto the irradiation surface of the optical disk, and the focus control of the laser light is performed based on the focus error signal. focus control means that can change the focus point stepwise; focus point moving means that moves and drives the focus point at least in a direction approaching the irradiation surface; and detecting the amount of reflected light of the laser beam reflected by the optical disk. , a reflected light amount detecting means that outputs a reflected light amount signal based on the reflected light amount signal, and a level region to which the reflected light amount level belongs among a plurality of level regions is detected by comparing the level of the reflected light amount signal and a predetermined reference value; and a loop gain setting means for inputting the area signal and selecting and setting the loop gain of the focus servo means in accordance with the input of the area signal.

Operation: First, the focus point is moved from a predetermined position in a direction approaching the optical disk, and when the amount of reflected light increases due to this movement, the loop gain is set based on the area signal, and then the focus control is performed. A state of focus control is achieved by means of means.

Description of examples Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic block diagram showing an optical disk recording/reproducing apparatus according to the present invention. The photosensor 1 has a light receiving section divided into four parts as shown in the figure, and outputs a current from each region according to the amount of light received. These currents are supplied to the current-voltage converter 3, where they are converted into voltages according to the amount of light. These voltages are summed in an adder 4 to form a read signal voltage. This voltage is subsequently processed to extract the desired information. Since this point is not related to the gist of the present invention, the explanation will be omitted.

On the other hand, high frequency components of the output of the adder 4 are smoothed by a low-pass filter 5, and this smoothed output is compared with a threshold value by a comparator 6, and a disk type output is generated based on the comparison result.

On the other hand, each voltage depending on the amount of light is
In order to detect a focusing error signal and a tracking error signal, the signals are added in pairs and then supplied to subtracters 7 and 8, respectively. When the objective lens in the optical pickup 13 is moved at a constant speed from a predetermined position toward the disk surface for focus adjustment, the subtracter 7 outputs a focus error signal as shown in FIG. 3a. At this time, the low-pass filter 5 outputs a light amount signal proportional to the amount of light incident on the photosensor 1 as shown in FIG. 3b. Here, the dotted line indicates the case of a disk with high reflectance, such as a playback-only disk.
The solid line indicates the case of a disk with low reflectance, such as a recordable and reproducible disk. Furthermore, the dashed line indicates the discrimination criterion. The point where the signal shown in FIG. 3a intersects the 0 point and the signal shown in FIG. 3b almost reaches its maximum value is the optimum position for focus.
On the other hand, in a steady state in which the focus drive device 9 and the tracking drive device 10 perform negative feedback control of the optical pickup 13 according to the error signals output from the subtracters 7 and 8, each drive The devices 9, 10 may be supplied with too much or too little signal. In this case, in order to avoid malfunctions, the gains of these drive devices 9 and 10 are switched by gain switchers 11 and 12 operated based on the output of the level lock circuit 32, and the respective loop gains are appropriately set.

According to this embodiment, the focus adjustment is started by a command from the focus search circuit 31 at startup, that is, when a new disk is inserted.
The focus search circuit 31 gives a command to the focus drive device 9 to move the objective lens in the optical pickup 13 from a predetermined position in a direction perpendicular to the disk surface to start a focus search, and at the same time, it starts a level lock. A command is given to reset the circuit 32 and set the gain of each drive device 9, 10 to a high value. On the other hand, as the objective lens 18 approaches the optimum focus point, and the output of the low-pass filter 5 exceeds a predetermined threshold, the level lock circuit 32 is immediately set, and the gains of each driving device 9, 10 are set low, and then the output of the low-pass filter 5 is set to a low value. This state will be maintained until it is reset. This reduces variations in loop gain in each tracking and focus servo state when playing an optical disc with low reflectance and when playing an optical disc with high reflectance. The focus lock circuit 33 detects and determines the optimum focus position from the outputs of the low-pass filter 5 and the subtracter 7, switches the focus drive device 9 to a normal servo function using a focus error signal, and performs steady-state focus adjustment. .

FIG. 2 is a schematic diagram showing the optical pickup and its driving parts. The light emitted from the laser diode 14 first passes through a collimator lens 15 into a parallel beam, then travels straight through a beam splitter 16, passes through a 1/4 wavelength plate 17, and is focused by an objective lens 18 to a pit on an optical disk 19. Focus near the surface. The reflected light follows the same path and reaches the beam splitter 16, but here it has already passed through the quarter-wave plate 17 twice, thereby undergoing a 90 degree rotation of the plane of polarization. Therefore, the direction can be changed by 90 degrees using the beam splitter 16. This light is further turned by 90 degrees by the prism 20 and reaches the 4-split photosensor 1. The output of the photosensor 1 is supplied to a tracking error detection circuit 8' and a focus error detection circuit 7'. These error detection circuits 7', 8' correspond to the subtracters 7, 8 in FIG. The error outputs of the error detection circuits 7', 8' are supplied to a focus drive device 9' and a tracking drive device 10', and these drive devices 9',
10' moves the whole or a part of the optical pickup 13 in the direction of the double-headed arrow for focus adjustment and tracking according to the error output.

The operation of the apparatus according to the present invention will be explained with reference to the flowchart of FIG. First, the device starts operating by rotating the disk. At this time, laser diode 1
The output of No. 4 is set to the reproduction power level. Next, in response to a command from the focus search circuit 31, the objective lens 18 in the pickup 13 starts moving toward the disk surface to perform a focus search, but at this time the level lock circuit 32 is reset. In this state, the comparator 6 monitors changes in the level of the amount of incident light as the pickup 13 moves closer to the disk surface, and if this exceeds a threshold value, it immediately sets the level lock circuit 32. Therefore, in this case, the gain switchers 11 and 12 are connected to the drive devices 9 and 10.
Set the gain low. Eventually pick up 1
3 reaches the optimum focus position, the focus lock circuit detects this, performs the focus lock described above, and ends the operation.

On the other hand, if the incident light amount level does not reach the threshold value, focus locking is performed without performing gain switching of the driving devices 9 and 10, and the operation is ended.

Note that, without being limited to this embodiment, for example, a plurality of criteria for determining the reflected light level may be provided, and the types based on the reflectance of the optical disk may be further classified into ranks, and the determination results may be displayed on an appropriate display. Various aspects are possible.

Effects of the Invention According to the device of the present invention, the loop gain of the control system for focusing, tracking, etc. is selected based on the reflectance of the recording medium itself of the optical disk. There is no need to newly provide a member to be detected for discrimination, and there is no need to provide a new optical means for optical disc discrimination in the device, which not only prevents the configuration of the device itself from becoming complicated, but also makes it easier to play. Complications in the process of preparing optical discs can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of an optical disk recording/reproducing apparatus according to the present invention, and FIG. 2 is a block diagram showing an optical pickup and its peripheral circuits.
FIG. 3 is a diagram for explaining the embodiment, and FIG. 4 is a diagram for explaining the embodiment.
3 is a flowchart showing the operation of the optical disc recording and reproducing apparatus according to the present invention. 1...Photo sensor, 3...Current voltage converter, 4
... Adder, 5 ... Low pass filter, 6 ... Comparator, 7, 8 ... Subtractor, 9, 10 ... Drive device, 11, 12 ... Gain switcher, 13 ... Optical pickup, 14 ... ...laser diode, 3
1... Focus search circuit, 32... Level lock circuit, 33... Focus lock circuit.

Claims (1)

[Claims for Utility Model Registration] The invention includes a focus error detection means for outputting a focus error signal of a laser beam irradiated onto an irradiation surface of an optical disk, and performs focus control of the laser beam based on the focus error signal. focus control means that can change the loop gain in steps; focus point moving means that moves and drives the focus point at least in a direction approaching the irradiation surface; a reflected light amount detection means for detecting the amount of reflected light and outputting a reflected light amount signal based on the detected amount; and a level region to which the reflected light amount level belongs among the plurality of level regions by comparing the level of the reflected light amount signal and a predetermined reference value. level detecting means for detecting and outputting a region signal indicating this; and loop gain setting means for inputting the region signal and selectively setting a loop gain of the focus servo means in accordance with the inputted region signal; The focus point is moved from a predetermined position in a direction approaching the optical disk, and when the amount of reflected light increases due to this movement, the loop gain is set based on the area signal, and then the focus control means controls the focus point. An optical disk recording and reproducing device characterized in that it is in a controlled state.