JPS63149841A - Disk inclination detector for optical information reader - Google Patents

Abstract

PURPOSE:To eliminate a need for an independent disk inclination detector by employing a four-sectional detector detecting a reflected light beam that includes an information from a recording surface, for the detection of disk inclination. CONSTITUTION:The four-sectional detector 7 consists of division parts 7a-7d, and is disposed so that its Y-axis coincides with the reproducing direction. Current-voltage converters 9-12 converts the respective detection currents of the parts 7a-7d to voltages. Adders 13, 14 respectively add the outputs of the converters 9, 10 respectively and those of the converters 11, 12, respectively, and their outputs come to be an RF signals that include DC components. HPFs 15, 16 and LPFs 17, 18 divide said RF signal into an RF signal and a DC component. Envelope detectors 19, 20 detect the RF signal, and converts it to a DC level. Dividers 21, 22 divide the detection outputs of the detectors 19, 20 by the outputs of the LPFs 17, 18, to make them modulation degree signals. A subtractor 23 obtains a difference signal from between the said modulation degree signals from the dividers 21, 22, and outputs a disk inclination signal 24.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical information reading device, particularly a disk tilt detection device used in an optical video disk player or the like.

[Conventional technology]

In general, in information reading devices for discs (optical discs), if the output optical axis of the objective lens that focuses light on the recording surface is not perpendicular to the recording surface, aberrations will occur in the spot on the recording surface, and the light will not be focused correctly on the read pit and will not be focused on the adjacent pit. It is known that reading even the signals of the 1-rack bits causes crosstalk. This crosstalk phenomenon is an unavoidable problem in an optical device in which the direction of the output optical axis of the objective lens is fixed because the disk warps during molding and due to changes over time. For this reason, for example,
The optical recording information reading device disclosed in Publication No. 5 is as follows:
Apart from the optical device for reading information, it has one light emitting element T-1 and two light receiving elements 2 and 3, as shown in FIG. A disk tilt detection device is provided which detects the tilt of the disk 5 using reflected light and tilts an optical device for reading information in accordance with the tilt of the disk 5.

[Problem that the invention seeks to solve]

The conventional optical recording information reading device described above requires a light emitting element and a light receiving element in addition to the optical device for reading information, which increases the cost of the optical information reading device. There are drawbacks such as the need for adjustment. In addition, this detection method detects light as an average amount of light across many tracks, so it is possible to correct malfunctions due to scratches on the disk, and to correct disk tilt up to the outermost periphery due to no reflection of light from the outer periphery near the outermost periphery of the disk. There are problems such as not being able to do so.

The present invention eliminates these problems and provides a disk tilt detection device for an optical information reading device that does not require a separate disk tilt detector and can accurately detect the tilt up to the outermost periphery without malfunction due to disk scratches. The purpose is to make it possible.

[Means for solving problems]

The configuration of the present invention adopted to solve the above-mentioned problems includes an optical means that focuses a light beam on a recording surface of a rotating disk, and a light beam that is reflected by the recording surface and contains information from the recording surface. In an optical information reading device having a 4-split photodetector for detecting a beam, two dark lines dividing the 4-split photodetector into 4 areas are located on the information disc at respective spot positions where the light is focused on the recording surface. means for obtaining first and second sum signals consisting of the sum of detection signals of two divided portions arranged so as to correspond to a normal line and a tangent line and divided by the dark line corresponding to the tangent line; , means for dividing the first and second sum signals into a high frequency band containing information signals and a low frequency band containing DC components; and means for envelope detecting the signals in the high frequency range. means for dividing the output of the envelope detection means by the signal in the low frequency band; and first and second signals obtained by the dividing means.
The first feature is that the inclination of the disk with respect to the output optical axis of the objective lens of the optical means is detected by subtracting or comparing the modulation signals of means for obtaining first and second signals, which are arranged to correspond to the tangent line of the disk at the spot position where the light is focused, and are each composed of detection signals of one divided portion that exists independently on both sides of the virtual line; and means for dividing the first and second signals into a high frequency 4W band including information signals and a low frequency band including a DC component.

means for envelope detecting the high frequency band signal; means for dividing the output of the envelope detecting means by the low frequency band signal; and subtracting or subtracting the first and second modulated signals obtained by the dividing means. In comparison, a second feature of the present invention is that it includes means for determining the inclination of the disk with respect to the optical axis of light emitted from the objective lens of the optical means.

[Effect]

In the present invention, a four-segment photodetector that detects a light beam that is reflected by the recording surface of a rotating disk and contains information from this recording surface is used to detect the disk tilt. The disc tilt can be detected accurately.

That is, the two dark lines that divide the four-split photodetector into four are each divided by two dark lines that correspond to the normal and tangent lines of the disk at the spot positions where the light is focused on the recording surface.
Either the first and second sum signals consisting of the sum of the detection signals of the four divided parts are used, or the virtual line passing through the center of the four-divided photodetector is connected to the tangent to the disk at the spot position where the light is focused on the recording surface. The modulation degrees of these signals are detected and compared using first and second signals consisting of detection signals of one divided section that exist independently on both sides of this virtual line. Therefore, malfunctions due to scratches on the disk are eliminated, and detection up to the outermost periphery of the disk is possible.

〔Example〕

Examples will be described below.

FIG. 1 is a block diagram of one embodiment, and numeral 6 indicates a pit row of the disk, and 7 indicates dividing portions 7a and 7b divided by X*[ll and Y axes that are perpendicular to each other.

A four-part photodetector consisting of 7c and 7d is shown.

A light beam travels along the pit row 6 of the disk in the direction of the arrow to perform reproduction, and the four-split photodetector 7 is arranged so that its reproduction direction coincides with the Y-axis.

The detection light beam 8 from the disk recording surface is divided into four parts by a detector 7
It focuses almost at the center above. 9, 10° and 11.12 are the divided portions 7a, 7b, 7c, and 7 of the 4-split photodetector 7, respectively.
Current-to-voltage converter 13.1 for converting each current of d into a voltage
Reference numeral 4 denotes an adder for the outputs of the current-voltage converters 11 and 12 of the current-voltage converters 9 and 10, respectively, and the output thereof is an RF multiplied signal with a DC component as shown in FIG. 2(a). A and C in this figure indicate the signals at positions A and C in FIG. 15.16 is bypass filter (HPF), 17.1
Reference numeral 8 denotes a low-pass filter (LPF) that separates the R and F signals having DC components into an RF multiplied signal and DC component. 19
．． 20 is an envelope detector which detects the RF signal and converts it to a DC level as shown in FIG. 2(b). B in this figure shows the signal at position B in FIG. 21.2
2 is a divider.

The detection outputs detected by envelope detectors 19 and 20 are divided by the outputs of low-pass filters 17 and 18 to obtain modulation degree signals. A subtracter 23 calculates the difference signal between the modulation degree signals from the dividers 21 and 22 and outputs a disc tilt signal 24 indicating the degree of disc tilt, and this disc tilt signal 24 is used as an error detection signal for a disc tilt correction device. can do.

The disk tilt detection operation by the disk tilt detection device of this embodiment will be explained. When the disk is tilted, the light beam on the disk recording surface produces comatic aberration. This coma aberration occurs in one direction with respect to the center of the pit row 6, and on the side where the coma aberration occurs, a lot of light is irradiated on the part of the mirror between the tracks. In the photodetector 7, as the average light amount increases, the amount of light diffracted by the pits decreases, and the degree of modulation decreases. Furthermore, since the modulation degree does not decrease on the side where coma aberration does not occur, it is possible to detect the disk tilt by comparing the two modulation degree signals.

FIG. 3 is a block diagram of another embodiment, in which the same parts as in FIG. 1 are given the same reference numerals, and the parts corresponding to those in FIG. Reference numeral 25 indicates a comparator for the modulation signal of the dividers 21 and 22. This disk tilt detection device differs from the embodiment shown in FIG.
A four-division photodetector 7' has an imaginary line passing through its center corresponding to a tangent to the disk at the spot position where the light is focused on the recording surface, and one division 7' on each side of the imaginary line.
b, 7' and d are connected to current-voltage converters 9 and 11, and a comparator 25 is used.

That is, in this embodiment, a four-split photodetector 7' divided by the X-axis and Y-axis, which are perpendicular to each other, is used for tilt detection.
For example, the detection signals of the respective dividing sections 7'b and 7'd are used in place of the sum signals A and C of the embodiment shown in FIG. 25 to detect the disk tilt direction and output a tilt detection signal 26.

According to these embodiments, since the information reading beam is used to detect the disc inclination, there is no need to separately provide a disc inclination detector, and the cost of the reproducing apparatus is reduced. Furthermore, since the tilt at the information reading position can be detected, malfunctions due to disk scratches are eliminated, and the tilt can be accurately detected up to the outermost periphery.

〔Effect of the invention〕

The present invention makes it possible to provide a disk tilt detection device for an optical information reading device that does not require a separate disk tilt detector and can accurately detect the tilt up to the outermost periphery without malfunctions due to disk scratches.

This has great industrial effects.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of the disk tilt detection device of the optical information reading device of the present invention, FIG. 2 is an explanatory diagram of the signal waveform of the main part of FIG. 1, and FIG. FIG. 4, a block diagram of the embodiment, is an explanatory diagram of a disk tilt detection device for a conventional optical information reading device. 7.7'... Four-split photodetector, 8... Detection light beam, 9.10, 11, 12... Current-voltage transformer, 13
゜14... Adder, 15.16... Bypass filter, 17.18... Low pass filter, 19.20.
...Envelope detector, 21.22...Divider, 2
3... (1 other person) East 2 + Figure C (α) Shipho Shina Sakai - Soen v Mi (b) ov4 Tei W Tory 1J Shiro Fable 4 - Prisoner

Claims (1)

[Scope of Claims] 1. An optical means that focuses a light beam on a recording surface of a rotating disk, and a four-split photodetector that detects a light beam that is reflected by the recording surface and includes information from the recording surface. In the optical information reading device, two dark lines dividing the four-split photodetector into four parts are arranged so as to correspond to a normal line and a tangent line to the disc at a spot position where the light is focused on the recording surface, respectively. means for obtaining first and second sum signals consisting of the sum of detection signals of two divided parts each divided by the dark line corresponding to the tangent line; means for dividing a high frequency band containing each information signal and a low frequency band containing a direct current component, means for envelope detecting the signal in the high frequency band, and output of the means for envelope detecting the signal in the low frequency band. and means for subtracting or comparing the first and second modulation signals obtained by the dividing means to determine the inclination of the disk with respect to the output optical axis of the objective lens of the optical means. A disk tilt detection device for an optical information reading device, characterized in that: 2. Optical information reading having an optical means that focuses a light beam on the recording surface of a rotating disk, and a 4-split photodetector that detects the light beam that is reflected by the recording surface and includes information from the recording surface. In the apparatus, the 4-split photodetector is arranged so that an imaginary line passing through the center thereof corresponds to a tangent to the disk at a spot position where the light is focused on the recording surface, and each of the 4-split photodetectors exists independently on both sides of the imaginary line. means for obtaining first and second signals consisting of the detection signals of the dividing section;
and means for dividing the second signal into a high frequency band including an information signal and a low frequency band including a DC component, a means for envelope detecting the signal in the high frequency band, and an output of the envelope detecting means. means for dividing by the signal in the low frequency band; and a first signal obtained by the dividing means.
and means for subtracting or comparing the second modulation signal to determine the inclination of the disc with respect to the output optical axis of the objective lens of the optical means. Device.