JPS6252735A - Optical information recording and reproducing device - Google Patents

Abstract

PURPOSE:To attain higher sensitivity and more accurate control by detecting and controlling the tilt of a disc and an optical axis from a high frequency component outputted from a photodetecting element. CONSTITUTION:The photodetecting element 6 is divided into two parts 61, 62 by a split line in parallel with the direction of track. Outputs of photodetecting elements 61, 62 are added by an adder circuit 20 and fed to a demodulation circuit, outputs of the photodetecting elements 61, 62 are fed to high pass filters 21, 22, where the low frequency component is shut, only the high frequency component is separated and extracted and given to a comparator 23. The output of the circuit 23 is smoothed by a low filter 27 and a tracking control circuit 31 controlling a ray fed to an angle adjusting means 30 via a compensation amplifier 29 so as to trace the track on the disc 5 activates the means 30 at the tracking control.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical information recording and reproducing apparatus for optically recording and reproducing information on a disc such as a video disc and a digital audio disc.

[Summary of the invention]

The present invention relates to an optical information recording and reproducing device, which includes a light source that emits a light beam for recording and reproducing information, a means for irradiating a disk with the light beam emitted from the light source, and a left and right direction parallel to tracks formed on the disk. a light-receiving element that is divided into at least two parts and receives the light beam that has passed through the disk;
and an adding circuit that adds the outputs of the two divided light receiving elements and outputs a signal related to information to be recorded and reproduced on the disk.

A high-pass filter separates and extracts high-frequency components from each output of the two divided light-receiving elements, a comparator circuit that compares each output of the high-pass filter, and a light beam directed toward the disk in response to the output signal of the comparator circuit. An angle adjustment means for adjusting the inclination of the axis is provided, and the inclination of the disk and optical axis is detected and controlled from the high frequency component output by the light receiving element, thereby simplifying the configuration and adjusting the inclination of the disk and optical axis. This makes it possible to adjust g with higher sensitivity.

[Conventional technology]

In order to accurately record and reproduce information in an optical information recording and reproducing device, it is necessary to accurately converge the light beam emitted from the light source onto a track on the disk, control tracking, and align the optical axis of the light beam with respect to the disk. It is desired that the relationship be (ideally perpendicular). From this perspective, FIG. 7 shows a conventional configuration for making the optical axis perpendicular to the disk.

In the figure, reference numeral 1 denotes a pickup that is moved relative to the disk 5 in the radial direction. The pickup 1 is a light source 2 such as a semiconductor laser that emits a light beam for recording and reproducing information.
and beam splitter 3.

It is composed of an objective lens 4 which serves as a means for converging and irradiating light beams onto the disk 5, and a light receiving element 6 which receives reflected light from the disk 5. 10 is a detection means fixed to the pickup 1 for detecting the inclination of the optical axis, and has two light emitting diodes 7 and two light receiving elements 8.9 arranged symmetrically with respect to the light emitting diodes 7. There is.

The effect will now be explained. Laser beams etc. emitted from the light source 2 are converged and irradiated onto the disk 5 via the beam splitter 3 and the objective lens 4. The light beam reflected by the disk 5 passes through the objective lens 4 to the beam splitter 3.
The light is reflected there and irradiated onto the light receiving element 6. Information can be reproduced from the output of the light receiving element 6.

By the way, as shown in FIG. 8, when the angle of the disk 5 with respect to the optical axis of the light beam from the light source 2 is tilted, the balance of the light amount of the light beam emitted from the light emitting diode 7 and incident on the light receiving element 8.9 changes. .

As a result, if the inclination of the optical axis (pickup 1) of the light beam from the light source 2 is controlled in accordance with the difference in output between the light receiving elements 8 and 9, the optical axis can be set in a predetermined relationship (ideally) with respect to the disk 5. can be held vertically).

[Problem that the invention seeks to solve]

However, in such a device, since the inclination of the optical axis is detected by the detecting means 1o, the inclination of the detecting means 10 itself with respect to the disk 5 may be detected due to installation errors.

It was not possible to accurately detect the inclination of the optical axis of the light beam for recording and reproducing information. In addition, a separate optical system for detecting tilt is required in addition to the optical system for recording and reproducing, which not only increases the number of parts but also requires space for it, which has the disadvantage of increasing the size of the device. Ta.

Means for Solving Problem C] FIG. 2 shows the basic configuration of the pickup 1 of the present invention. A light source 2 consisting of a gas laser such as a He-N e laser or a semiconductor laser, a beam splitter 3 that separates incident light and reflected light, an objective lens 4 that converges the light beam onto a disk 5, a light receiving element 6 such as a photodiode, etc. The configuration of the pickup 1 is the same as in FIG.

In the present invention, something like a special detection means 10 is not provided, and instead, as shown in FIG. 1, the light receiving element is 6 is divided into at least two parts 61,62. Alternatively, as shown by the broken line in the figure, the light-receiving element 6 is divided into four by two dividing lines that form 45 degrees with the track, and the light-receiving element 6 is positioned on the left and right in the direction parallel to the track.
1.62 can also be used. And each light receiving element 61
．． The outputs of 62 are added by an adder circuit 20 and supplied to a demodulation circuit (not shown). Further, the output of each light-receiving element 61 , 62 is supplied to a high-pass filter 21 , 22 , the low-frequency component thereof is cut off, and only the high-frequency component (RF multiplied signal) is separated and extracted and output to the comparison circuit 23 . The comparison circuit 23 includes, for example, each high-pass filter 21 .
Detection circuit 24.2 that detects the envelope of the output of 22.
5, and a differential amplifier 26 that outputs the difference between the signals output by the detection circuits 24 and 25. The output of the comparison circuit 23 is smoothed by a low-pass filter 27 and supplied to the angle adjustment means 30 via a compensation amplifier 29 having a variable resistor 28 provided as required.

A tracking control circuit 31 controls the light beam to follow the track on the disk 5, and activates the angle adjustment means 30 when tracking control is being performed.

[Effect]

The effect will now be explained. A light beam emitted from a light source 2 passes through a beam splitter 3, enters an objective lens 4, and is converged onto a disk 5.

The light beam reflected by the disk 5 is incident on the beam splitter 3 via the objective lens 4, where it is reflected and irradiated onto the light receiving element 6. Since the amount of reflected light changes due to modulation by pits etc. on the disk 5, the light receiving elements 61 and 62
The information signal can be reproduced by demodulating the addition output of the addition circuit 20, that is, the output of the addition circuit 20.

For example, if the disk 5 is tilted in the radial direction relative to the pickup 1 and the optical axis of the light beam is not perpendicular, comatic aberration etc. will occur. At this time, the RF multiplied signal level outputted by the adder circuit 2o becomes as shown by the curve a in FIG. 3, and the tracking error signal becomes as shown in the curve a.

That is, the RF multiplied signal level is maximum at the track center (point ◯), whereas point A, where the tracking error signal becomes zero, is shifted from point 0. The deviation between point O and point A is approximately proportional to coma aberration, that is, the inclination of the disk 5. In other words, when the inclination of the disk 5 is zero, there is no deviation between the two, and the direction and amount of deviation are uniquely determined by the direction and amount of the inclination.

Therefore, by detecting the direction and amount of deviation between points A and O, the direction and amount of tilt of the disk 5 can be detected.

The tracking servo loop is then closed, and the tracking control circuit 31 controls the position of the objective lens 4, for example, to cause the light beam to accurately follow the track. Then, the tracking error signal becomes approximately zero, so by detecting the RF multiplied signal level at this time, it is possible to substantially detect the deviation between points A and O. That is, when the light spot 63 moves on the light receiving element 6 in a direction perpendicular to the dividing line, the RF multiplied signal level output from each of the light receiving elements 61 and 62 becomes as shown by curves ai and a in FIG. 4, respectively. Therefore, the RF multiplied signal difference signal outputted by the light receiving elements 61 and 62 becomes a signal proportional to the inclination of the disk, as shown by the straight line C in FIG.

For this reason, high-pass filters 21.22 separate and extract RF multiplied signals, which are high-frequency components, from the outputs of the light-receiving elements 61.62. Each RF multiplied signal level (for example, envelope) is detected by the detection circuits 24 and 25, and the difference signal is outputted from the differential amplifier 26. This difference signal is smoothed by a low-pass filter 27 to remove high-frequency noise components. In reality, it is not always optimal for the optical axis to be perpendicular to the disk 5 due to various factors, so the output of the low-pass filter 27 is input to a compensation amplifier 29 as a differential amplifier, and Positive and negative voltage ±V
By changing the sliding point of the variable resistor 28 to which the voltage is supplied and adjusting the reference voltage, the predetermined offset is compensated and then input to the angle adjustment means 30. Angle adjustment means 3
0 is activated by the tracking control circuit 31, the angle of the pickup 1 with respect to the disk 5 is changed and adjusted in response to the input signal from the comparison circuit 23. As a result, the servo is applied so that the output of the comparison circuit 23 becomes equal to the reference voltage (ideally zero) of the compensation amplifier 29.

In principle, it is possible to obtain the angle adjustment signal from the difference signal between the low-frequency components of the outputs of the light receiving elements 61 and 62, but in this case, it is not only difficult to distinguish it from the tracking error signal, but also the angle adjustment signal is not sufficiently sensitive. is difficult to obtain. Therefore, as in the present invention, it is preferable to generate the angle adjustment signal from the RF multiplied signal level or phase.

In the above, the RF multiplied signal level is detected by the comparator circuit 23, but for example, as shown in FIG.
It is also possible to further improve the sensitivity by comparing the phases of the RF multiplied signals from the high-pass filters 21 and 22 using the phase comparator 23 and adjusting the angle in response to the error signal.

〔effect〕

As described above, the present invention provides an optical information recording/reproducing device that includes:
A light source that emits light beams for recording and reproducing information, a means for irradiating the light beams emitted from the light source onto the disk, and a device that is divided into at least two parts on the left and right sides in a direction parallel to the tracks formed on the disk, Add the output of the light receiving element that receives the light beam and the light receiving element that is divided into two,
An adder circuit that outputs a signal related to information recorded and reproduced on a disc, a high-pass filter that separates and extracts high-frequency components from each output of the two divided light receiving elements, and a comparison circuit that compares each output of the high-pass filter. and an angle adjustment means for adjusting the inclination of the optical axis of the light beam with respect to the disk in response to the output signal of the comparison circuit, so that the inclination of the disk and the optical axis is detected and controlled from the high frequency component outputted by the light receiving element. As a result, more sensitive and accurate control is possible than in 4, and 5
Since the number of parts is small, space is small and costs can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the optical information recording/reproducing apparatus of the present invention, FIG. 2 is a schematic side view of its optical system, FIGS. 3, 4, and 5 are its characteristic diagrams, and FIG. 6 is a schematic side view of its optical system. The block diagrams of other embodiments, FIGS. 7 and 8, are schematic side views of the optical system of a conventional optical information recording/reproducing apparatus. 1...Pickup 2...Light source 3...Beam splitter 4...Objective lens 5...Disc 6.8.9.
61.62... Light receiving element 7... Light emitting diode
10...Detection means 20...Addition circuit 21.22...High pass filter 23...Comparison circuit 24.25...Detection circuit 26...Differential amplifier 27...Low pass filter 29...・Compensation amplifier 30...Angle adjustment means 31...Tracking control circuit 63...Spot Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 8 r

Claims (1)

[Claims] a light source that emits a light beam for recording and reproducing information; a means for irradiating the disk with the light beam emitted from the light source;
A light receiving element is divided into at least two parts on the left and right sides in a direction parallel to the tracks formed on the disk, and receives the light beam that has passed through the disk, and the outputs of the two divided light receiving elements are added together. Compare each output of the high-pass filter with an adder circuit that outputs a signal related to information recorded and reproduced on a disk, and a high-pass filter that separates and extracts high-frequency components from each output of the divided light receiving element. An optical information recording/reproducing apparatus comprising: a comparison circuit; and an angle adjustment means for adjusting the inclination of the optical axis of the light beam with respect to the disk in accordance with the output signal of the comparison circuit.