JPH0482051A - Disk discriminating device - Google Patents

Abstract

PURPOSE:To eliminate a need of focus search operation by using the light from a light source in a skew sensor and comparing the signal level, which is obtained by receiving the return light from a disk by a photodetector, with a prescribed reference level to discriminate the disk type. CONSTITUTION:The light from a light emitting diode 2c in a skew sensor 2 is reflected by a disk 1, and the return light is received by two-divided photo diodes 2A and 2B, and the total sum signal of quantities of light received by these photo diodes is outputted from an adder 5 of a skew servo system. The output signal from the adder 5 is supplied to one input terminals of each of three comparators 19 to 21 for disk type discrimination. Reference voltage from three reference voltage sources 15 to 17 are supplied to the other input terminals of comparators 19 to 21. These reference voltages La to Lc are so set that the difference in level of the sum signal of quantities of return light based on the difference in reflectivity of the disk can be discriminated. Thus, the disk type is discriminated in a short time.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a disc discriminating device, and more particularly to a disc discriminating device for discriminating between a plurality of types of discs having different reflectances.

B1 Summary of the Invention The present invention provides a disc discriminating device for discriminating the types of discs having different reflectances, which includes: illuminating the disc with light from a light source within a skew sensor for detecting the inclination of the disc; The reflected light is received by a light-receiving element in the skew sensor, and the output signal level from the light-receiving element is compared with a predetermined reference level to determine the disc type. Furthermore, the disc type can be determined without adversely affecting the recording medium.

C3 Prior Art In recent years, disk-shaped recording media such as optical disks and magneto-optical disks that utilize optical or magneto-optical signal recording and reproducing methods have been developed and are being supplied to the market.

These disk-shaped recording media include continuous-only type (so-called ROM type) recording media such as so-called compact discs, and write-once type (so-called write-once type) where the user can write data once. ), and recording media on which data can be rewritten (so-called overwrite date), such as magneto-optical disks, are known.

For optical disc stems that can use these various disc-shaped recording media, it is desirable to be able to automatically determine the type of disc loaded. The disc type is determined by comparing the amount of returned light with a predetermined reference amount of light.

That is, for example, in FIG. 3, a laser beam emitted from a laser diode 3o, which is a laser light source, is converted into a parallel light beam by a collimator lens 31, and the PB
The objective lens 33 is
The image is projected onto the optical disc 34 via the . optical disc 3
The return light reflected by 4 is incident on a beam splitter 32 via an objective lens 33, reflected by the beam splitter 32, and guided to a photodetecting element, such as a photo diode 35.

Specifically, the intensity of the returned light obtained by extracting the output signal from the photodiode 35 via the current-voltage converter 36 or the like is as shown in FIG. 4, for example.

In FIG. 4, the horizontal axis shows the objective lens 33 and the optical disk 34.
, and the intensity of the return light from the optical disk 34 is plotted on the thin axis, respectively, indicating the amount of return light that changes as the objective lens moves in the optical axis direction when performing a so-called focus search operation. . Each curve a in this figure 4
, b and C are the types of disks installed,
ROM disks such as the above-mentioned compact disks, magneto-optical (MO) disks, and write-once (W) disks such as the above-mentioned compact disks,
O) The case of a disk is shown. It is assumed that the ROM disk is of an aluminum (Af) reflective film type.

As is clear from Fig. 4, not only do the physical characteristics of various types of discs differ depending on the material they are made of, but also the reflectance of the discs also differs. The maximum value of the returned light intensity appears differently for each disk. Set each voltage corresponding to the maximum value of the returned light intensity to a predetermined base! 1! By comparing with the voltage, the type of disc can be determined. In other words, in order of the maximum amount of laser return light, the ROM type (Af reflective film), the magneto-optical (MO) type, and the write-once (WO
) type.

D9 Problems to be Solved by the Invention By the way, in the case where the disc type is determined by detecting the return light from the laser light source which is the main light source as described above, when performing the focus search, it is necessary to If the loop gain of the focus servo is not switched, the servo gain may be insufficient or the servo circuit may oscillate, causing an abnormality in the focus search operation before the disk type determination is complete.

Further, since the above-described determination is repeated until the type of disc is determined, the number of times focus search is performed increases, and the time required until focus servo is applied increases.

In particular, in magneto-optical disks, which are recording media that allow data to be rewritten (so-called override) depending on the intensity of the laser light source, the disk is irradiated with strong laser output light from the main light source during the focus search described above. This may cause deterioration over time, leading to erroneous erasure, erroneous writing, signal deterioration, etc.

The present invention has been proposed in view of the conventional situation as described above, and provides a disc discrimination device that can reliably discriminate the disc type in a short time and without adversely affecting the optical disc. The purpose is to

E1 Means for Solving the Problems In order to solve the above-mentioned object, the disc type discrimination device according to the present invention is a device for discriminating multiple types of discs having different reflectances, and includes a skew sensor for detecting the inclination of the disc. The disc is irradiated with light from a light a (for example, a light emitting diode) within the skew sensor, the reflected light is received by a light receiving element within the skew sensor, and the level of the output signal from this light receiving element is compared with a predetermined reference level. It is characterized in that the type of disc is determined by this.

F1 action The disc discriminating device according to the present invention uses light from a light source in the skew sensor to compare the signal level of the return light from the disc received by the light receiving element with a predetermined reference level. Disc type discrimination is performed without using light from a main light source such as light, and focus search operations and the like are not required.

G. Examples Hereinafter, specific examples of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a schematic configuration of main parts and peripheral parts of a disc discrimination device according to an embodiment of the present invention.

In the embodiment shown in FIG. 1, the configuration for determining the types of discs having different reflectances will be briefly described. Light from the light emitting diode 2C in the figure) is irradiated onto the disc 1, and the reflected light is sent to the light receiving element in the skew sensor 2 (photodiode F'2A in Figure 2).
, 2B), and these photodiodes 2A, 2
The output from B is taken out via amplifiers 3A, 3B, adder 5, etc., and the output signal level is sent to comparators 19 to 21, and each unit! 1! The disc type is determined by comparing with predetermined reference levels L, -Lc from the voltage sources 15-17. Specific examples of disk types include the so-called ROM type, which is for playback only, and the magneto-optical (
MO) type, write-once (W◯) type, etc., and each reference level L, ~Lc is set in advance to a level that can distinguish each of these types.

Here, with reference to FIG. 1, the structure and operation of a so-called skew servo that controls the inclination of the optical head 11 in accordance with the detection output of the inclination of the disk l will be described.

FIG. 2 shows the internal structure of the skew sensor 2 for detecting the inclination of the disc and the presence or absence of the disc, and its positional relationship with respect to the disc I. In FIG. 2, the skew sensor 2 is provided with one light emitting diode (LED) 2C as a light emitting element and two divided photodiodes 2A and 2B as light receiving elements. The direction of arrow T in FIG. 2 indicates the track tangent direction (tangential direction) of the disk 1, and the direction of arrow R indicates the radial direction. A light emitting diode 2C is arranged with a shift, and two-split photodiodes 2A and 2B are arranged in symmetrical positions shifted by an equal distance from the center of the sensor in the direction of arrow R.
is located. A light beam emitted from the light emitting diode 2C is reflected by the disk l, and the returned light is detected by the two-split photodiodes 2B and 2C. The inclination (radial direction) of the disk l is determined by the subtracted output (error output) of the output signals detected here, and the presence or absence of the disk l is determined by the summed output of each detection signal.

That is, the signals detected by photodiodes 2A and 2B in FIG. 1 and amplified by amplifiers 3A and 3B are sent to S, respectively.
A, Sl, these signals S^, Ss are supplied to the subtracter 4 to obtain a subtracted output signal S AS s, and supplied to the adder 5 to obtain an added output signal S
A +3. is now available. Each output signal from the subtracter 4 and adder 5 is sent to a positive error detector 6, and also to a negative error detector 7, respectively. Furthermore, the output signal from the adder 5 is input to a disk presence/absence detector 18 , and its detection output is supplied to the motor driver 9 .

Further, the output signals from the positive error detector 6 and the negative error detector 7 are amplified by the error amplifier 8 and sent to the motor driver 9 to control and drive the skew motor 10. This skew motor 10 changes the tilt angle of the optical recording and/or reproducing light:/F1 1 with respect to the disk 1, and corresponds to the detected tilt of the disk 1 (radial direction tilt). Skew servo control is performed to adjust the inclination of the optical henode 11. Note that the light nozzle 11 includes, for example, a laser light source, a light receiving element, a lens system,
The optical head 11 is configured to include a beam splitter, etc., and a reproduction system 12 and/or recording system 13 provided in association with the optical head 11, and a system controller 14 that controls reproduction and/or recording operations, 1, normal recording and/or playback is performed.

Next, a configuration for determining the type of disc will be described.

From the adder 5 of the skew servo system mentioned above, the light from the light emitting diode 2C in the skew sensor 2 is reflected by the disk 1 and returns to the photodiode 2A which is split into two.
, 2B is output. The output signal from the adder 5 is supplied to one input terminal of each of three comparators 19 to 21 for disc type discrimination. The other input terminal of each comparator 19-21 has three groups 1! Each reference voltage is supplied from voltage sources 15 to 17, respectively. These three bases 1!
Voltage if! 15.16.17 each reference voltage La, Lb,
Lc is set so as to be able to discriminate the difference in the level of the sum signal of the amount of returned light based on the difference in the reflectance of the disk. The output signals from each comparator 19-21 are supplied to a disc type detection circuit 22, and the determination results are outputted to each output terminal 23-25.

The disc discrimination device according to the embodiment of the present invention includes a skew sensor 2
As explained in conjunction with FIG. Disc discrimination is performed by focusing on the difference in the output (total sum of output). Here, as a specific example, an aluminum (A2) reflective film type read-only ROM disk and a magneto-optical (MO
) disk and write-once (WO) disk, in descending order of reflectance: aluminum (A) reflective film type ROM disk, magneto-optical (MO) disk, and write-once (WO) disk. Since it is a disk, the intensity of the returned light is also in this order.In other words, as the average value of the output level from the adder 5, the level corresponding to the intensity of the returned light from the aluminum (Al) reflective film type ROM disk is set as Ll, magneto-optical. (MOI) 0 for disks)
Assuming that the level is L3 in the case of a write-once (WO) disc, Ll>Lm>Li.

Here, a predetermined basis is used as a dark value for distinguishing between a ROM disk and a magneto-optical (MO) disk. The ll voltage level should be smaller than and larger than Ll (L I>
L a > L t ) is required. That is, by inputting a reference voltage level La that satisfies this condition to one terminal of the comparator 19, it is possible to discriminate between a ROM disk and a magneto-optical (MO) disk based on the "H" and "L" outputs. I can do it.

However, if the output from the comparator 19 is "L", there is a possibility that the disc is a write-once (WO) disc. Next, a predetermined reference voltage level Lb, which is a dark value for distinguishing between a magneto-optical (MO) disk and a write-once (WO) disk, is smaller than Ll and larger than L3 (Ll
>Lb>17. ) is required and this group! 1! By inputting the voltage level Lb to one terminal of the comparator 20,
It becomes possible to distinguish between magneto-optical (MO) disks and write-once (WO) disks. Furthermore, a third reference voltage level Lc
By setting the level to a level that satisfies the condition (L:+>Lc>0) and inputting this level Lc to one terminal of the comparator 21, it is determined whether the disc is a write-once (WO) disc or there is no disc. It becomes possible to do so. In this way, using the three comparators 19 to 21, it is possible to determine whether there is any of the three types of discs or no disc. However, the actual disc discrimination output signal is one H" (high level) for each disc type.
Since it is preferable to use a form in which an output can be obtained, the output signals from each of the comparators 19 to 21 are sent to a disk type detection circuit 22 to convert the output form. As a specific example of the signals output from each of the output terminals 23 to 25 of the disc type detection circuit 22, in the case of the Affi reflective film type ROM disc, only the output from the terminal 23 is °H'
Therefore, for a magneto-optical (MO) disk, only the output from the terminal 24 becomes ``H'', and for a write-once (WO) disk, only the output from the terminal 25 becomes ``H''. This is preferable for performing circuit function switching control etc. according to each disc type.

Outputs from the comparators 19 to 21 (inputs to the disk discrimination circuit 22) and output terminals 23 to 25 from the disk discrimination circuit 22 during the disk type discrimination operation as explained above.
Regarding the output to (a) A1 reflective film type reproduction only R
OM disk [with] magneto-optical (MO) disk (C) write-once (WO) disk (d) No disk A summary of each case is shown in Table 1 below.

Table 1 As is clear from this Table 1, each comparator 19 to 21
By manually inputting the output from the disc to the disc discriminating circuit 22 and converting the output format, one "H" (high level) output can be selectively obtained for each disc type. In the disk discrimination circuit 22, (a) Affi
When identifying a reflective film type playback-only ROM disk,
If the output of comparator 19 is “°H”, the other comparator 2
Regardless of the level of 0.21, only the output from the output terminal 23 is set to "H", and the output from the output terminals 24.25 is set to "L". Similarly, (b) magneto-optical (
MO) If it is determined that it is a disk, the output of the comparator 19 is “
If the output of the comparator 20 is "H" at "L", the output from the output terminal 23.25 is set to "L" regardless of the level of the comparator 21, and the output from the output terminal 24 is set to "L". The output is set to "H".

(C) When determining a write-once (WO) disc, if the level of comparator 19.20 is °'L'' and the level of comparator 21 is H''', output from output terminal 23.24. is set to "L", and the output of the output terminal 25 is set to "H".Finally, (when determining that there is no DL disk, each comparator 1
When all outputs from 9 to 21 are "L", output terminals 23 to 21
The output from 25 is at the same level as the comparator above, ``L''.
“It’s closed.

As described above, a comprehensive determination of various disk types is performed based on the comparison signal between the reference level assigned to the comparator and the detected signal level in each comparator.

The result of the disc type determination described above is supplied to each unit that switches, for example, focus servo gain, tracking servo gain, and laser power. By determining the type of disc, the disc identification during recording or playback operation is completed when the disc is placed on the mounting table and the skew servo is activated, so the signal can be played back or recorded after the player starts. The time taken can be shortened. Further, it is possible to optimize the laser power and control each signal processing circuit. For example, in the case of write-once type discs such as magneto-optical discs, optimization of laser power prevents erroneous erasing, erroneous writing, signal deterioration, etc. that occur when discs are identified using conventional high-output main light source lasers. can.

Further, the above method can determine the mta of a disk even if it is not stored in a cart storage or the like.

H1 Effects of the Invention As is clear from the above explanation, the disc discrimination device according to the present invention detects the light emitted from the light source in the skew sensor that detects the inclination of the disc as reflected light from the disc, By comparing the signal level with a predetermined reference level, it is possible to identify two discs in a short time with stable operation.

Furthermore, since powerful light such as laser light is not used, erroneous erasure or erroneous writing of data on the disk can be prevented, and signal deterioration can be avoided.

Furthermore, by using the already installed skew servo to determine the disc type, the above effect can be achieved without the need to add new optical system components, and it is possible to achieve the above effect without the need to add new optical system components. This makes it possible to identify the type of disc even if it is a disc.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the disc discriminating device according to the present invention and a schematic configuration of its peripheral parts, Fig. 2 is a plan view showing a disc and a skew sensor, and Fig. 3 is a conventional disc discriminating device. FIG. 4 is a graph showing the relationship between the intensity of returned light and the type of disc when performing a focus search. 2A, 2B ・ 2C ・ ・ ・ 15, 16. 19, 20. 22 ・ ・ ・ ・ ・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・ to… to detect skew a skew detector, light emitting device, reference voltage source, comparator, SF type detection circuit patent

Claims (1)

[Claims] A disc discriminating device for discriminating the types of discs having different reflectances, the disc is irradiated with light from a light source in a skew sensor for detecting the inclination of the disc, and the reflected light is used to detect the skew of the disc. 1. A disc discriminating device characterized in that the type of disc is determined by receiving light with a light receiving element within a sensor and comparing the output signal level from the light receiving element with a predetermined reference level.