JP2000099962A - Optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of a focus error between an astigmatic optical system and a reproducing information signal detecting optical system due to a change in an environmental temp. by detecting a distance change caused by a temperature change from a condenser lens to an optical detecting means and controlling a distance from a collimator lens to a light source or an executed light source based on a detecting signal from a distance change detecting means. SOLUTION: In a focus error detecting system A1, light is made incident through a condenser lens 8 and a cylindrical lens 9 on a four-division photodetector 10 and a group of photodetecting sections 10A and 10C and a group of photodetecting sections 10B and 10D are provided in point symmetric positions. A comparator 10E outputs a comparison signal between the total output of the group of photodetecting sections 10B and 10D and the total output of the group of photodetecting sections 10A and 10C as a focus error signal to a focus driving circuit. The set position of a condenser lens 6 is decided so that reflected light beams passed through it are converged on all photodetecting cells constituting a multiple-division photodetector 7A.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk apparatus capable of simultaneously reproducing a plurality of tracks formed on an optical disk in an optimum focus state.
The present invention relates to a technique for preventing a focus offset error and maintaining a good reproduction state.

[0002]

2. Description of the Related Art At present, as an optical disk device capable of simultaneously reproducing a plurality of tracks formed on an optical disk, one disclosed in Japanese Patent Application Laid-Open No. 8-249720 is known. This optical disk device includes a wide-area illumination source such as a laser array that can simultaneously irradiate a plurality of tracks formed on the optical disk, and light reflected from the optical disk by being illuminated by the wide-area illumination source. A light detecting means for detecting, and means for synthesizing light in a direction along a track detected by the light detecting means (in a radial direction of the optical disk around the track to be detected) are provided.

Here, as the above-mentioned light detecting means, the number of light detectors in the radial direction of the optical disk is set to be sufficiently larger than the number of tracks so that an optical image reproduced from each track can be sufficiently resolved. It is configured using a large number (approximately four times or more) of photodetectors. Such photodetectors include PD (photo diode), PIN-PD (PIN-p
hoto diode or CCD (charge coupled devic)
Regardless of e), not only a sensor in one row in the radial direction but also a detector such as a TDI (Time Delay and Integration) / CCD sensor, which has been integrated in the time axis direction in a two-dimensional arrangement, may be used.

The focus servo in an optical disk reproducing apparatus for reproducing a plurality of tracks on an optical disk at the same time is the same as that in a general optical disk reproducing apparatus for reproducing only one track. For example, detection is performed using a plurality of divided photodetectors (for example, a four-divided photodetector), and as is well known, a focus error signal is generated by calculating the output of each divided light, and the position of the objective lens is adjusted accordingly. Do. Specifically, a focus error signal is generated from a detection signal light detected by a light detection unit different from an information signal detection unit that detects light of information signals of a plurality of tracks. Alternatively, a focus error signal is generated from a detection signal light detected by a split photodetector provided separately from a pickup optical system having a photodetector for detecting such an information signal.

[0005]

By the way, in the above-mentioned optical disk apparatus for simultaneously reproducing a plurality of tracks on an optical disk, the length of the astigmatism optical system for providing astigmatism for generating a focus error and the reproduction time are described. If the length of the reproduction information signal detecting optical system for detecting the information signal is significantly different, there is a problem that an offset occurs in the focus error when the environmental temperature changes.

Hereinafter, the optical system of a known optical disk device that receives reflected light from only one track on an optical disk and the above-described optical disk device that reproduces a plurality of tracks on an optical disk at the same time. The difference in the structure of the optical system will be described. That is, in the above-described known optical disk device that receives reflected light from only one track on the optical disk, the laser light emitted from the laser light source is formed on the optical disk via a collimator lens, a half mirror, and an objective lens. Illuminated the truck,
The reflected light reflected from the optical disk by this irradiation is reflected again by the half mirror via the objective lens, and after passing through the condenser lens, is irradiated to the four-divided sensor which is a multi-divided photodetector. It performs error detection and signal detection.

In such a configuration, the collimator lens and the condenser lens can be used in common, or a half mirror can be provided between the laser light source and the collimator lens. This is because in a known optical disk device that receives reflected light from only one track on an optical disk,
The same optical system can be used for the astigmatism optical system (focus error detection system) and the reproduction information signal detection optical system, or both can be provided close to each other.

On the other hand, in the above-described optical disk apparatus for simultaneously reproducing a plurality of tracks on an optical disk, a laser beam emitted from a laser light source irradiates a track formed on the optical disk via a collimator lens, a half mirror, and an objective lens. Due to this irradiation, the reflected light reflected from the optical disk is reflected again by the half mirror via the objective lens, and after passing through the imaging lens (= condensing lens), is reflected by another half mirror and the astigmatism optical system. And the light reaching the reproduction information signal detection optical system. In this optical system, the physical dimensions of the sensor constituting the reproduction information signal detection optical system limit the size of the collimator lens. Reproduction information signal detection of the focal length and the reflected light from the half mirror inserted in the optical path from the collimator lens to the objective lens The focal length of the imaging lens Sensahe condensing academic system, as will be described later, becomes something different significantly.

More specifically, the focal length fc of the collimator lens is determined by the spread of the illumination spot on the optical disk or the coupling efficiency of light from the laser light source to the objective lens. The focal length fi of the imaging lens is about 7 times as long as the objective lens, because the minute pits on the optical disk are projected on a larger photodetector (sensor) in an enlarged manner. Is several tens of times (about 30 to 100 times) the focal length of.

Assuming that the lateral magnification in the optical system for providing astigmatism in the optical disk device is m1 = fc / fo, and the lateral magnification in the reproduction information signal detection optical system is m2 = fi / fo. The lateral magnification m1 in the optical system that gives more astigmatism is about 2 to 7, and the lateral magnification m2 in the reproduction information signal detection optical system is about 30 to 100.

However, when the environmental temperature changes, the length of each part of the pickup constituting the optical disk device changes linearly with respect to the environmental temperature. For this reason, the optimal focus state for forming the best image of the pits on the optical disc deviates from the state before the temperature change.

On the other hand, when attention is paid to each sensor in the astigmatism optical system and the reproduced information signal detection optical system, there is a position on the optical disk where each sensor is correctly focused (just-focused). It is sufficient that this focus point after the change of the environmental temperature coincides with the above-mentioned optimal focus point, but it does not always coincide with the above-mentioned reason for the following reason.
That is, the amount of change in the length to the optimum focus point of each sensor in the astigmatism optical system and the reproduction information signal detection optical system before and after the environmental temperature change can be determined by considering the vertical magnification. It changes in proportion to the square.

However, since the length changes in proportion to the focal length fc of the collimator lens and the focal length fi of the imaging lens, when the lateral magnifications m1 and m2 are not equal, Even if the optimal focus state (optimal focus point) is obtained in the four-segmented photodetector of the astigmatism optical system, the sensor in the reproduction information signal detection optical system is not necessarily irradiated with correctly focused light. Not been.

Here, when the focus is detected by the astigmatism method, the optimum focus point in the astigmatism optical system is:
It does not coincide with the optimum focus point in the reproduction information signal detection optical system, and a focus error (focus offset) occurs between the two sensors.

However, in a known optical disk device that receives reflected light from only one track on an optical disk, the difference between the lateral magnifications m1 and m2 is small, so that there is no significant focus error, which is a problem. In a system in which the astigmatism optical system and the reproduction information signal detection optical system are located separately as in the optical disc device, there is a large difference in the lateral magnifications m1 and m2. A large focus error occurs.

The present invention has been made by paying attention to the above-mentioned points. Even when an environmental temperature change occurs, an astigmatism optical system (focus error detection system) and a reproduction information signal detection optical system are used. It is an object of the present invention to provide an optical disc device that can prevent a large focus error from occurring between the two sensors and maintain a good information signal reproduction state.

[0017]

In order to solve the above-mentioned problems, an optical disk apparatus according to the present invention converts a laser beam emitted from a light source into a parallel laser beam by a collimator lens and transmits the laser beam through a half mirror and an objective lens. An illumination optical system for irradiating a light spot on a plurality of tracks of the optical disc, and reflecting the light reflected from the plurality of tracks on the optical disc by the irradiation of the light spot and reflected via the objective lens and the half mirror. An information signal detection system in which one of the reflected light is condensed through a condenser lens and detected as a reproduced information signal by a light detection means; A focus error detection system that detects the focus error using the astigmatism method by entering the other reflected light via the mirror and using the astigmatism method , In the optical disk apparatus having,
Distance change detecting means for detecting a distance change due to a temperature change from the condenser lens to the light detecting means in the information signal detecting system; and the collimator in the illumination optical system based on a detection signal from the distance change detecting means Distance change control means for controlling a distance from a lens to the light source or a substantial light source.

Further, the distance change detecting means comprises an electric resistance change detecting section provided in parallel with a support member for supporting the condenser lens and the light detecting means in the information signal detecting system. The resistance change detection unit, when a DC voltage is applied to both ends of the support member, detects a change in length due to a change in temperature of the support member as a change in current value due to a change in electrical resistance value, A detection signal is output to the distance change control means.

Further, the distance change detecting means is provided at a position equivalent to a length from the light collecting lens to the light detecting means of a support member for supporting the light collecting lens and the light detecting means in the information signal detecting system. And an optical means for optically detecting a change in length caused by a change in temperature of the support member using an astigmatism method, and detecting a detection signal of the distance by the distance. The data is output to the change control means.

Further, the distance change detecting means includes an electric resistance portion engaged with a support member for supporting the condenser lens and the light detection means in the information signal detection system, and an electric resistance portion in parallel with the resistance portion. The electric resistance change detecting section is provided with a change in length caused by a temperature change of the supporting member when a DC voltage is applied to both ends of the electric resistance section. Is detected as a change in current value due to a change in electric resistance value, and a detection signal is output to the distance change control means.

Further, the distance change control means is constituted by an electromagnetic circuit based on Fleming's left hand rule, comprising a coil and a magnet provided to support the collimator lens in the illumination optical system, Moving the collimator lens in the illumination optical system in the axial direction based on a detection signal from the distance change detection means, and controlling a distance from the collimator lens in the illumination optical system to the light source or a substantial light source. It is a feature.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The basic structure of an optical disk reproducing apparatus according to an embodiment of the present invention will be described below with reference to FIG. The optical disc reproducing apparatus according to the present embodiment has the configuration shown in FIG.
As shown in FIG. 1, the optical system includes a focus error detection system A1, an information signal detection system A2, and an illumination optical system A3, which are astigmatism optical systems. In FIG. 1, D indicates an optical disk, s indicates a light spot, and s1 indicates a light spot on a photodetector.

The optical disk D has two recording layers D1 and D2 each having a plurality of tracks formed concentrically or spirally at a position of 0.6 mm or 1.2 mm in thickness.
By performing focus control of irradiating a light beam for each recording layer to be reproduced so as to obtain an in-focus optical image, the same as in the case of having a conventional single recording layer Thus, it is possible to obtain an optical image in a focused state, that is, an optical image in which an optical image based on reflected light from a pit array forming each track and an optical image based on reflected light from between tracks are sequentially arranged in parallel.

First, the focus error detection system A1 will be described. The focus error detection system A1 includes a condenser lens 8, a cylindrical lens 9, and four light detection units 10
It comprises a quadrant photodetector 10 composed of A, 10B, 10C, and 10D, and a comparator 10E that detects a focus error based on detection signals of the quadrant photodetector 10. Here, a case will be described in which an astigmatism method is used as a focus error detection system, and a four-segment photodetector is used for focus error detection. A two-segment photodetector, a six-segment photodetector, or the like may be used.

Further, unlike the example described here, it is also possible to adopt a configuration in which the information signal and the focus error are detected on the same optical path. For this purpose, a configuration using a diffractive optical element or a configuration in which a focus error is detected using a light beam on the detector other than the one used for detecting an information signal can be considered. However, in an optical disk reproducing apparatus that simultaneously reproduces a plurality of tracks on an optical disk, the fact that the focal length of the collimator lens and the focal length of the condenser lens to the sensor cannot be changed significantly. Can fit.

One of the two reflected light beams split by the half mirror 5 is incident on a four-divided photodetector 10 via a condenser lens 8 and a cylindrical lens 9. The quadrant photodetector 10 includes four photodetectors 10A, 10B, 1
0C and 10D, and a pair of light output detection units 10
A, 10C and a pair of photodetectors 10B, 10D are both provided at point-symmetric positions. The comparator 10E is configured to calculate the combined calculation power of the pair of photodetectors 10B and 10D and the pair of photodetectors 1B and 10D.
A comparison signal obtained by comparing the combined calculation powers of 0A and 10C is output as a focus error signal to a focus drive circuit (not shown). Normally, in the focused state, the comparator 10E does not output a focus error signal. Here, the focus error signal output from the comparator 10E of the focus error detection system A1 is a focus position error signal mainly responsible for controlling the objective lens 4, and is a signal having a wide bandwidth.

Next, the information signal detection system A2 will be described. The information signal detection system A2 includes a half mirror 5, a condenser lens 6, a multi-segment photodetector 7A, and a parallel input-serial output conversion circuit 7B. The focal length and the set position of the condenser lens 6 are determined so that the reflected light beam transmitted therethrough is condensed on all the photodetection cells constituting the multi-segmented photodetector 7A. The multi-segmented photodetector 7A is constituted by assembling a large number of photodetection cells arranged in a mesh pattern, and is, for example, a CCD. Further, as another embodiment, the multi-segment photodetector 7A can detect even a single row of photodetection cells.

Here, for the sake of explanation, the multi-divided photodetector 7A shown in FIG. 1 merely shows one row of such photodetection cells arranged in a mesh pattern.
In an actual multi-segmented photodetector, many columns of such photodetection cells are arranged in the row direction x and the column direction y.

The reflected light beams simultaneously reflected from the respective pit rows and between the tracks on the disk D by the irradiation of the light spot s again pass through the objective lens 4 to the reflecting mirror 3, the half mirror 2, and the half mirror 5 again. Is branched into two.
One reflected light beam split here is emitted to the focus error detection system A1, and the other reflected light beam is emitted to the information signal detection system A2.

Further, the illumination optical system A3 will be described. The illumination optical system A3 includes a surface light source 11, a collimator lens 1, a half mirror 2, a reflection mirror 3, and an objective lens 4. The surface light source 11 does not emit laser light in a single-like mode, and emits laser light with an emission width of about 50 μm to 100 μm. The laser diode LD as a light source is a surface light source. This embodiment includes a laser diode LD, a lens L, and a fiber F.

The laser light emitted from the surface light source 11 is converted into parallel laser light by the collimator lens 1, passes through the half mirror 2, is reflected by the reflection mirror 3, and is reflected on the disk D via the objective lens 4. A light spot s is formed on a plurality of tracks. The light spot s is irradiated so as to straddle the twelve tracks Tr1 to Tr12 in the radial direction. Incidentally, when the track width is about 0.3 μm and the track pitch is about 0.74 μm, the light spot s is formed with a width of at least about 9 μm in the radial direction.

The reflected light beams simultaneously reflected from the pit rows on the 12 tracks and between the tracks by the irradiation of the light spot s are reflected again by the reflecting mirror 3 and the half mirror 2 via the objective lens 4. After that, the light is branched into two by the half mirror 5. One reflected light beam split here is emitted to the focus error detection system A1, and the other reflected light beam is emitted to the information signal detection system A2.

In the optical disk device having the above-described optical configuration, it is necessary to increase the magnification from the disk to the sensor mainly due to the limitation of the size of the light detection cell of the sensor. For example, assuming that the cell size is 10 μm and a resolution for forming an image of a 0.2 μm area on the disk is considered, this magnification is 50 times. On the other hand, the magnification from the disc to the light source depends on the size of the light source, the spread angle, and the like, but is in the category of several times.

The above is summarized as follows. Lateral magnification m1 of the illumination optical system A3 in the optical disk device
If the focal length of the collimator lens 1 is fc and the focal length of the objective lens 4 is fo, then m1 = fc / fo, while the lateral magnification m2 of the information signal detection system A2 is When the distance is fi, m2 = fi / fo. Generally speaking, the lateral magnification m1 of the illumination optical system A3
Is about 2 to 7 times, and the lateral magnification m2 of the information signal detection system A2 is several tens of times (about 30 to 100 times).

Here, as a prelude to the description of the focus offset, a change in the length of each part due to a change in temperature will be considered.
The linear expansion coefficient of the member supporting the illumination optical system A3 is α1, and the linear expansion coefficient of the member supporting the information signal detection system A2 is α2. The change in length when the temperature rises by T is represented by a change ΔC in the illumination optical system A3, which is ΔC = {T · α1 · fc, and a change in the information signal detection system A2}. i becomes Δi = ΔT · α2 · fi.

As described above, when the environmental temperature changes, the length of each part of the pickup constituting the optical disk reproducing device changes linearly with respect to the environmental temperature. In addition, the focal length of each constituent lens also changes due to this temperature change. Naturally, this change also affects the focus detection. As described above, in a system in which the length of the focal length fc of the collimator lens 1 and the length of the focal length fi of the condenser lens 6 are greatly different from each other, the difference in magnification caused by the difference is considered. The resulting impact is dominant in impact. Therefore, in the following description, for simplicity of discussion, the focal length is treated as being constant regardless of the temperature.

Based on the above, the influence of the above-described change in the length on the focus detection is determined by the surface light source 11 → collimator lens 1 → objective lens 4 → disk D → objective lens 4 →
The state of the optical image on the multi-divided photodetector 7A of the condensing lens 6 → information signal detection system A2 will be described with reference to FIG. In FIG. 2, (a) is a reference state where there is no temperature change, (b) is a state after temperature change, and (c)
Is for explaining the principle of the present invention.

Here, the position of the image of the multi-split photodetector 7A by the objective lens 4 when the multi-split photodetector 7A is an object after a temperature change and the objective lens when the surface light source 11 is an object. If the position of the image of the surface light source 11 according to No. 4 matches, the focus offset does not occur.

Here, in FIG. 2B, the differences Δd1 and Δd2 between the original focus position and the image point position of the objective lens 4 after the temperature change are expressed by the following equations. Note that this equation can be immediately obtained from the formula for the longitudinal magnification of the lens. Δd1 = Δc · fo · fo / fc / fc Δd2 = Δi · fo · fo / fi / fi

The generated focus offset ΔZ
Is obtained as follows with reference to FIG. ΔZ = (Δd1 + Δd2) / 2−Δd2 = (Δd1−Δd2) / 2

As shown here, the change in length due to the temperature change is proportional to the focal length, while the change in the focal position is proportional to its square. For this reason, the optimal focus state for forming the best image of the pit on the optical disk is shifted from the state before the temperature change. The present invention has been made to prevent such a focus offset from occurring.

As a measure for preventing the occurrence of the focus offset, in the present invention, a length change (distance change) due to a temperature change of the information signal detection system A2 is detected, and based on the detection, a multiple division detection by the objective lens 4 is performed. Position of the image of the device 7A and the objective lens 4 when the surface light source 11 is an object
2 so that the position of the image of the surface light source 11 by
The position of the collimator lens 1 in the illumination optical system as shown in FIG.

That is, a signal corresponding to the distance from the condenser lens 6 in the information signal detection system A2 to the multi-divided photodetector 7A is detected, and based on the detected signal, the signal from the collimator lens 1 in the illumination optical system A3 to the surface light source is detected. The distance to the light source 11 or a substantial light source is changed to prevent the occurrence of a focus offset error.

Here, the following method can be adopted as a specific detection method for detecting a signal corresponding to the distance from the condenser lens 6 to the multi-divided photodetector 7A in the information signal detection system A2. (A) A change in the electrical resistance value of the support member that determines the distance from the condenser lens 6 to the multi-divided photodetector 7A in the information signal detection system A2 is detected. (B) Optically detect a change in the distance of the support member that determines the distance from the condenser lens 6 to the multi-divided photodetector 7A in the information signal detection system A2. (C) Detecting a change in the resistance value of the electrical resistance of the member engaged with the support member that determines the distance from the condenser lens 6 to the multi-divided photodetector 7A in the information signal detection system A2.

As a method for changing the distance from the collimator lens 1 to the surface light source 11 or the substantial light source in the illumination optical system A3 based on the above-described detection signal, a magnetic circuit based on Fleming's left-hand rule is used. Method can be adopted.

FIG. 3 is a block diagram showing a specific configuration of the distance change detecting means according to the above (a). As shown in FIG. 3, the distance change detecting means is an electric resistance change detecting unit 13 provided in parallel with a support member 12 supporting the condenser lens 6 and the multi-divided photodetector 7A in the information signal detection system A2. When the DC voltage E is applied to both ends of the support member 12, the electric resistance change detection unit 13 detects a change in length caused by a change in temperature of the support member 12 and a change in electric current caused by a change in electric resistance value. The change is detected as a value change, and the detection signal is output to a distance change control unit including the control unit 14 and the distance change unit 15.

Assuming that the length of the support member 12 is L, the coefficient of linear expansion of the support member 12 is α1, and the temperature change is ΔT, the length L ′ of the support member 12 after the temperature change is L ′ = L + α1 · Δ
It changes to T. Here, when the support member 12 is a conductive material, or when the support member 12 is non-conductive, but a conductive film is formed on the surface of the support member 12 by a chemical treatment or the like, Since the length of the support member 12 changes, its electrical resistance value also changes.

In the configuration shown in FIG. 3, utilizing this principle, a DC voltage E is applied to both ends of the support member 12, and an electric resistance change detecting section 13 (general ammeter) is provided in parallel with the support member 12. Thus, a change in length caused by a change in temperature of the support member 12 is detected as a change in current value, and the detected change in current value is sent to the control unit 14. The control unit 14 controls the illumination optical system A3 based on the change in the current value.
The signal for controlling the distance changing means 15 is generated for the distance from the collimator lens 1 to the light source LD or the substantial light source.

The distance changing means 15 for changing the distance from the collimator lens 1 to the light source LD or the substantial light source in the illumination optical system A3 is designed to prevent a focus error from being offset based on a signal from the control unit 14. Collimator lens 1 in illumination optical system A3
The light source or the substantial light source.

In the above description, for the sake of simplicity, the method of applying the DC voltage E to both ends of the support member 12 has been described. It is desirable that the length be equal to the length between the condenser lens 6 and the multi-divided photodetector 7A in the signal detection system A2.

Next, FIG. 4 is a block diagram showing a specific configuration of the distance change detecting means according to the above (b). The distance change detecting means 15 shown in FIG.
The objective lens 1 provided at a position equivalent to the length from the condenser lens 6 of the support member 12 supporting the condenser lens 6 and the multi-divided photodetector 7A to the multi-divided photodetector 7A
6 and a mirror 17 and are constituted by optical means 18 for optically detecting a change in length due to a temperature change of the support member 12 by using an astigmatism method, similarly to the focus error detection system A1. The detection signal is output to the distance changing means 15 via the control unit 14.

FIG. 5 is a block diagram showing a specific configuration of the distance change detecting means according to the above (c). The distance change detecting means shown in FIG. 5 includes an electric resistance portion 19 engaged with the support member 12 supporting the condenser lens 6 and the multi-divided photodetector 7A in the information signal detection system A2, The electric resistance change detecting section 13 is provided in parallel with the section 19, and the electric resistance change detecting section 13 is configured such that when a DC voltage E is applied to both ends of the electric resistance section 19,
It is configured to detect a change in length due to a change in temperature of the support member 12 as a change in current value due to a change in electric resistance value, and output a detection signal to the distance changing unit 15 via the control unit 14. ing.

As in the description of the distance change detecting means shown in FIG. 3, when the length of the support member 12 is L, the coefficient of linear expansion of the support member 12 is α1, and the temperature change is ΔT, The length L ′ of the support member 12 is L ′ = L + α1 · Δ
However, if the electric resistance portion 19 is engaged with the support member 12 by bonding, screwing, or the like, the electric resistance portion 19 engaged with the support member 12 changes with the temperature change of the support member 12.
Also changes.

In the configuration shown in FIG. 5, utilizing this principle, a DC voltage E is applied to both ends of the electric resistance portion 19 engaged with the support member 12, and the electric resistance is applied in parallel with the electric resistance portion 19. By providing the dynamic resistance detection unit 13 (a general ammeter), a change in length caused by a change in temperature of the support member 12 is detected as a change in current value, and the change in current value detected here is detected by the control unit. Send to 14. The following operation is the same as the operation in FIG.

FIG. 6 shows the distance from the collimator lens 1 in the illumination optical system A3 to the light source LD or the substantial light source based on the distance change detection signal obtained by the above-described configuration shown in FIGS. FIG. 4 is a block diagram illustrating a configuration of a distance change control unit that performs change control.

The distance change control means shown in FIG. 6 comprises an electromagnetic circuit 22 based on Fleming's left-hand rule composed of a coil 20 and a magnet 21 provided to support the collimator lens 1 in the illumination optical system A3. And moves the collimator lens 1 in the axial direction to control the relative distance from the collimator lens 1 to the light source LD or the substantial light source in the illumination optical system A3. With this configuration, it is possible to prevent the occurrence of an offset in the focus error.

In this way, the position of the collimator lens 1 in the illumination optical system is set so that the position of the image of the sensor by the objective lens and the position of the image of the light source by the objective lens when the light source is an object are the same. Is changed, the astigmatism optical system (focus error detection system) and the information signal detection system can be used even when the environmental temperature changes.
It is possible to prevent a large focus error from occurring between the two sensors, and to maintain a good information signal reproduction state.

[0058]

As described above, according to the optical disk apparatus of the present invention, the distance change due to the temperature change from the condenser lens to the light detecting means in the information signal detecting system is detected.
Since the distance from the collimator lens in the illumination optical system to the light source or the substantial light source is changed based on the detected change in distance, even when the environmental temperature changes, the astigmatism optical system ( It is possible to prevent a large focus error from occurring between the two sensors of the focus error detection system) and the reproduction information signal detection optical system, and to maintain a good information signal reproduction state.

[Brief description of the drawings]

FIG. 1 is a block diagram for explaining a configuration of an optical disc reproducing apparatus according to the present invention.

FIG. 2 is an explanatory diagram for explaining occurrence of a focus offset error due to a temperature change.

FIG. 3 is a block diagram illustrating an example of a distance change detection unit according to the present invention.

FIG. 4 is a block diagram showing another example of the distance change detecting means according to the present invention.

FIG. 5 is a block diagram showing still another example of the distance change detecting means according to the present invention.

FIG. 6 is a block diagram showing an example of a distance change control unit according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Collimator lens 2, 5 Half mirror 3 Reflection mirror 4 Objective lens 6, 8 Condensing lens 7A Multi-segment photodetector (light detection means) 10 4-segment photodetector 12 Supporting member 13 Electric resistance change detecting unit 14 Control unit 15 Distance changing means 16 Objective lens 17 Mirror 18 Optical means for optically detecting using astigmatism method 19 Electrical resistance section 20 Coil 21 Magnet 22 Electromagnetic circuit based on Fleming's left hand rule A1 Focus error detection system A2 Information Signal detection system A3 Illumination optical system LD Laser diode (light source)

Claims (5)

[Claims] 1. An illumination optical system for converting a laser beam emitted from a light source into a parallel laser beam by a collimator lens, and irradiating a light spot on a plurality of tracks of an optical disk via a half mirror and an objective lens; The reflected light reflected from a plurality of tracks on the optical disc by the irradiation and reflected through the objective lens and the half mirror is bifurcated through a branching half mirror, and one of the reflected lights is condensed. An information signal detection system that is condensed via a lens and detected as a reproduced information signal by a light detection unit; and the other reflected light branched via the branching half mirror is incident on the information signal detection system using an astigmatism method. An optical disk device comprising: a focus error detection system that detects a focus error by using the focusing lens in the information signal detection system. A distance change detecting means for detecting a distance change due to a temperature change from the light detecting means to the light detecting means; and from the collimator lens to the light source or a substantial light source in the illumination optical system based on a detection signal from the distance change detecting means. An optical disc device, comprising: distance change control means for controlling the distance of the optical disk. 2. The information processing apparatus according to claim 1, wherein the distance change detection unit includes an electric resistance change detection unit provided in parallel with a support member that supports the condenser lens and the light detection unit in the information signal detection system. The resistance change detection unit, when a DC voltage is applied to both ends of the support member, detects a change in length due to a change in temperature of the support member as a change in current value due to a change in electrical resistance value, 2. The optical disk device according to claim 1, wherein a detection signal is output to said distance change control means. 3. The distance change detecting means is a position equivalent to a length from the light collecting lens to the light detecting means of a support member for supporting the light collecting lens and the light detecting means in the information signal detecting system. And an optical means for optically detecting a change in length caused by a change in temperature of the support member using an astigmatism method, and detecting a detection signal of the distance by the distance. 2. The optical disk device according to claim 1, wherein the signal is output to a change control unit. 4. An electric resistance section engaged with a support member for supporting the condenser lens and the light detection section in the information signal detection system, wherein the distance change detection section is provided in parallel with the resistance section. It is composed of a provided electric resistance change detection unit,
The electric resistance change detecting unit, when a DC voltage is applied to both ends of the electric resistance unit, changes the length due to the temperature change of the support member, the change in the current value accompanying the change in the electric resistance value. 2. The optical disk device according to claim 1, wherein the detection is performed as a detection signal, and a detection signal is output to the distance change control unit. 5. The distance change control means is configured by an electromagnetic circuit based on Fleming's left-hand rule, comprising a coil and a magnet provided to support the collimator lens in the illumination optical system, Moving the collimator lens in the illumination optical system in the axial direction based on a detection signal from the distance change detection means, and controlling a distance from the collimator lens in the illumination optical system to the light source or a substantial light source. 5. The optical disk device according to claim 1, wherein: