JPS63103471A - Optical disk discriminating circuit for compatible optical disk device - Google Patents

Abstract

PURPOSE:To discriminate optical disks whose reflection factors are different from each other, by detecting whether a detected value is higher or lower than a set value, and discriminating the optical disk, based on said detection. CONSTITUTION:When an optical disk 1 is loaded, it is rotated at a prescribed linear velocity, and also, the convergent light of laser of a prescribed output is radiated to the optical disk 1 through an objective lens L2, and the reflected laser light which is reflected erroneously by a track and a pit is detected by a detector 4. Subsequently, it is compared with a reference voltage outputted from a reference voltage source 6b by a comparator 6c through an adder circuit 5 and an amplifier 6a, and when the detecting signal has become higher than the reference voltage, a rectangular wave corresponding to its signal waveform is outputted. In accordance with whether this rectangular wave signal exists or not, whether the optical disk is an additional type or a reproduction exclusive type is discriminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical disc discrimination circuit for discriminating the type of optical disc used in a compatible optical disc device.

[Conventional Example] In recent years, various devices using optical disks have been proposed. In particular, CD (compact disc) devices are showing rapid growth. Furthermore, the types of optical discs that can be loaded into these devices are becoming more diverse. Therefore, compatible optical disc devices capable of loading these optical discs have been proposed.

Some of these compatible optical disc devices distinguish optical discs based on the size of their radius, for example. That is, for example, this compatible optical disc device is provided with two reflective sensors inside, one of which is located at a predetermined distance from the center of the turntable, and the other reflective sensor is located at a predetermined distance from the center of the turntable. placed at a further distance. In this case, when an optical disk with a relatively small radius is loaded, the reflective sensor closer to the turntable detects the optical disk, but the other reflective sensor does not detect the optical disk. Further, when an optical disk with a relatively large radius is loaded, the two reflective sensors detect the optical disk. Based on this detection result, it is possible to discriminate between large and small diameter optical discs.

[Problems to be Solved by the Invention] However, the optical disc discriminating device of the above-mentioned compatible optical disc device is effective in the case of optical discs with different radii, but has a problem in that it cannot discriminate in the case of optical discs with the same radius.

This invention was made in view of the above-mentioned problems, focusing on the fact that, for example, read-only optical discs and write-once (DRAW) optical discs have different light reflectances. An object of the present invention is to provide an optical disc discrimination circuit for a compatible optical disc device that can perform discrimination.

[Means for Solving the Problems] In order to achieve the above object, an optical disc discrimination circuit for a compatible optical disc device of the present invention includes a detection circuit that uses a detector to detect reflected light from an optical disc loaded in a compatible optical disc device. A comparison means is provided for comparing the detection value detected by the detector with a preset setting value, the magnitude of the detection value with respect to the setting value is detected, and the optical disc is discriminated based on the detection. It is something.

[Function] When an optical disc is loaded into a compatible optical disc device,
When an optical disc is irradiated with focused laser light, the reflected laser light from the optical disc is detected by a detector. This detected value is compared with a preset value by a comparing means.

Depending on the magnitude of the detected value relative to the set value, it is determined which type of optical disc is loaded, such as a write-once type or a read-only type, having a different reflectance.

[Implementation example] Embodiments of the present invention will be described below based on the drawings.

In FIG. 1, laser light from a laser diode LD is irradiated onto an optical disk 1 via a collimator lens L1, a mirror 2) and an objective lens L2, and the laser beam reflected by the optical disk 1 is reflected by the objective lens L2) as a polarized beam It is guided to a detector 4 via a splitter 3. In addition,
A quarter wavelength plate is provided on the mirror 2 side of the polarizing beam splitter 3. This detector 4 is, for example, a four-divided detector consisting of four detectors A, B, C, and D as shown in FIG.
・Detect the intensity distribution of the laser beam, and calculate the detected values a and b.
, c, and d are output to the adder circuit 5, respectively. Addition circuit 5
outputs, for example, the detected sum value of (a+b+c+d) to the comparing means 6, which is the discriminating circuit of the present invention. This comparison means 6
includes an amplifier 6a that amplifies the detected sum value to a predetermined value, a reference voltage source 6b, and a comparator 6c that compares the detected sum value with the reference voltage output from the reference voltage source 6b.

Next, the operation of the optical disc discriminating circuit of the compatible optical disc device having the above configuration will be explained with reference to 75 in FIG.

First, when the optical disc 1 is loaded into the compatible optical disc device, the compatible optical disc device rotates the optical disc 1 at a constant linear velocity and moves the optical pickup head to a predetermined position. At this time, the optical disc 1 is irradiated with focused laser light of a constant output via the objective lens L2 of the optical pickup head. Therefore, this focused spot light passes through the tracks and pits of the optical disc 1. The reflected laser light that is reflected after passing through the tracks and pits is detected by a detector 4. This detection is performed when the optical disc 1 is rotating with surface wobbling or eccentricity, and when the optical disc 1 is focused on the recording surface of the optical disc 1, even without using automatic focus control of the optical pink-up head for the optical disc 1. It is also done by groups and pits when they cross the track due to eccentricity.

If the detector 4 is, for example, a four-split detector, the detected values a, b, c, and d are added by an adding circuit 5.

Further, the adder circuit 5 cuts the DC component of the signal photoelectrically converted by the detector 4. This added signal is amplified by an amplifier 6a with a predetermined amplification degree.

Here, the loaded optical disc 1 is, for example, writeable (DRA).
In the case of a W) type optical disc, the amplifier 6a outputs a signal from the amplifier 6a after the optical pickup head moves to a predetermined position.
) is output.

Furthermore, if the loaded optical disc 1 is a read-only disc, the amplifier 6a outputs the signal from the amplifier 6a during the same period as shown in FIG.
The detection signal shown in b) is output. Note that section E in FIG. 3 corresponds to the detection of reflected light from the unrecorded portion of the optical disc 1, and sections F and G correspond to the detection of reflected light from the recorded portion of the optical disc 1. Detection voltage V,, V2.
V has the relationship of Vl<V, <■, and as a result of measurement in this example, v2 is approximately 240 mV, and ■3 is approximately 35 mV.
It was 0 mV. Comparing this detection voltage for read-only optical discs and write-once optical discs, ■ and ■.

There was a difference of approximately 110 mV between them.

In this way, the detection signal output from the amplifier 6a is converted to the reference voltage Vr output from the reference voltage source 6b by the comparator 6C.
The reference voltage V ref to be compared with ef is determined based on the reflectance of the optical disc to be discriminated. The detection voltage is set between the detected voltages v2 and v3. As a result, when the detection signal becomes larger than the base Q voltage V ref, the comparator 6C outputs a rectangular wave corresponding to the signal waveform. That is, the comparator 6c does not output any signal when the detection signal shown in FIG. 3(a) is input, and outputs a rectangular wave signal when the detection signal shown in FIG. 3(b) is input. do. Depending on the presence or absence of this rectangular wave signal, for example, the CPU determines whether it is a write-once type optical disc or a read-only type optical disc. For example, even if the discs are read-only optical discs, if there is a difference in the detected voltage due to differences in manufacturers, the reference voltage Vref can be set accordingly, and the optical discs can be identified.

Note that for this determination, it is sufficient to irradiate the optical disc 1 with focused laser light and focus the reflected light on the detector 4, and automatic focus control of the optical pickup head is not required.

Further, the results of this optical disk discrimination can also be used as data for offset and gain settings of servo circuits and the like that will be controlled later.

[Effects of the Invention] As explained above, according to the discrimination circuit of the compatible optical disc device of the present invention, the detection value of the reflected light from the optical disc is compared with a preset value, and the signal is determined based on this comparison. Since the output comparison means is provided, it is possible to discriminate between optical disks loaded in the compatible optical disk device by the signal output from the comparison means, even if the optical disks have the same radius but have different reflectances. Also,
According to the present invention, since only a few circuits such as an amplifier, a reference voltage, and a comparator are added to the conventional detection circuit, the circuit configuration can be simple and the cost can be reduced.

[Brief explanation of the drawing]

Fig. 1 shows an embodiment of the present invention; Fig. 2 is a circuit diagram of an optical disc discriminating circuit of a compatible optical disc device; Fig. 2 is a schematic diagram of a four-division detector for detecting reflected laser light from an optical disc; FIG. 3 is a time chart diagram showing detection signals of reflected laser light from the . In the figure, 1 is an optical disk, 4 is a detector (four-division detector),
6 is a comparison means, 6a is an amplifier, 6b is a reference voltage source, 6C
is a comparator. Patent Applicant: Fujitsu General Co., Ltd. Agent, Patent Attorney: Takuya Ohara's Story of Hitsuyama Figure 3

Claims (3)

[Claims] (1) A detection circuit for detecting reflected light from an optical disc loaded in a compatible optical disc device with a detector is provided with a comparison means for comparing a detected value detected by the detector with a preset value, and the set value is A compatible optical disc device characterized in that the optical disc is determined based on the magnitude of the detected value with respect to the detected value. (2) In claim (1), the detector includes four
1. A compatible optical disc device, wherein the compatible optical disc device is a divided detector, and the comparing means compares a sum of detection values of the four-divided detector with the set value. (3) In claims (1) and (2), the comparison means includes an amplifier that amplifies the detected value or the sum of the detected values, and amplifies the amplified detected value or sum and the set value. A compatible optical disc device, comprising: a comparator for comparing the .