JP2002190125A - Optical head device, optical information recording/ reproducing apparatus, method for detecting aberration, and method of adjusting optical head device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical head device in which a spherical aberration detection signal is stably obtained for a high-density optical disk. SOLUTION: Returned light from an optical disk is split into two of transmitted light and diffracted light by a hologram element 108 and so forth. Information is reproduced by the transmitted light, which has a large amount thereof. The diffracted light, which has a small amount thereof, is split into two of a region near the optical axis and a region far from the optical axis, in which respective out-focus amounts are obtained as focus error signals. The differential signal thereof is defined as a spherical aberration error signal. Accordingly, an amount of spherical aberration may be detected, in which a high SN (signal to noise) ratio is maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head device for obtaining a spherical aberration error signal for controlling a spherical aberration correcting means used when recording or reproducing information on an information storage medium such as an optical disk or an optical card. And an information recording / reproducing apparatus for recording / reproducing information on / from an information storage medium, an aberration detecting method, and a method for adjusting an optical head device.

[0002]

2. Description of the Related Art FIG. 28 is a configuration diagram of an optical head device in a conventional information recording / reproducing apparatus. Light emitted from a semiconductor laser 101 as a light source becomes parallel light by a collimator lens 102 and passes through a beam splitter 103. The beam transmitted through the beam splitter 103 is condensed by an objective lens 105 on an optical disk 107 as an information storage medium. The focused beam is reflected and diffracted by a track on the optical disk 107. The reflected and diffracted beam passes through the objective lens 105 again, is reflected by the beam splitter 103, and is detected by the detection lens 109.
The light is focused. The focused beam is applied to the cylindrical lens 110
As a result, the track is given astigmatism in the 45-degree direction, and enters the photodetector 901.

FIG. 29 is a front view of the photodetector 901 shown in FIG. The light detector 901 includes detection areas 911 to 91
4 are arranged vertically and horizontally, and the beam 951 given astigmatism is adjusted so as to come to the center of the detection area. The focus error signal is obtained by subtracting the sum signal of the two detection areas arranged diagonally from the sum signal of the two detection areas arranged opposite diagonally. The track error signal is obtained by comparing the phase of the sum signal of two detection areas arranged diagonally and the sum signal of the two detection areas arranged opposite diagonally.

The objective lens 105 shown in FIG. 28 is moved by an actuator 106 in a direction perpendicular to a track and in a focus direction. The movement in the track orthogonal direction is performed by the tracking control system based on the track error signal,
The movement in the focus direction is performed by a focusing control system based on the focus error signal. Here, it is assumed that an astigmatism method is used as a means for generating a focus error signal. Also, it is assumed that the means for generating the track error signal uses a phase difference method.

[0005]

Here, in order to increase the density of information recorded on the optical disk 107 as an information storage medium, a system has been proposed in which the numerical aperture NA of the condensing optical system is increased and the wavelength is shortened. Have been. However, as the numerical aperture NA increases, the spherical aberration generated due to a thickness error of the base material serving as the protective layer of the optical disc 107 increases. As means for correcting this, there are known a method of generating a spherical wave by an objective lens by generating a spherical wave by a set of lenses, and a method of generating a reverse spherical aberration by a liquid crystal. However, there was no suitable method for detecting spherical aberration.

For this reason, as the density of information recorded on the information storage medium increases, the requirements for optical conditions become stricter, and the beam cannot be narrowed down sufficiently on the information storage medium due to spherical aberration and the like. I ca n’t record stably,
There is a problem that information cannot be reproduced stably.

The present invention has been made in view of the above problems, and has as its object to provide an optical head device capable of stably obtaining a spherical aberration detection signal even for a high-density optical disk.
An information recording / reproducing device capable of stably recording and reproducing information,
An object of the present invention is to provide an aberration detection method and an adjustment method for an optical head device.

[0008]

In order to achieve the above-mentioned object, a first optical head device according to the present invention comprises a light source for emitting light and a light emitted from the light source condensed on an information storage medium. And a return light reflected by the information storage medium into a first light having a large light amount and a second light having a small light amount as compared with the first light. Branching means;
First light detecting means for receiving the first light and outputting a signal for reproducing information recorded on the information storage medium;
And a second light detection unit that outputs a signal for detecting the aberration of the light collected on the information storage medium.

In the first optical head device, the branching means divides the second light into light in a first area near the optical axis and light in a second area far from the optical axis, and the first optical head The apparatus detects a spherical aberration amount of light condensed on an information storage medium using at least one of a defocus amount of light in a first area and a defocus amount of light in the second area. It is preferable to include an aberration detecting unit.

In this case, it is preferable that the spherical aberration detecting means determines the difference between the defocus amount of light in the first area and the defocus amount of light in the second area as the amount of spherical aberration.

The cross section of the light used in the condensing optical system is a substantially circular shape having a first radius, and a circular region having a second radius smaller than the first radius and concentric with the substantially circular shape. Is a first region, and a region outside the first region and inside a substantially circle having a first radius is preferably a second region.

It is preferable that the amount of defocus of light in the first area and the amount of change of defocus of light in the second area when the relative distance between the information storage medium and the light condensing means change.

The second light detecting means has a first light detecting area for detecting light in the first area, and a second light detecting area for detecting light in the second area. The light detection area of 1 is
It is preferable that the first light beam branched by the branching unit is located closer to the optical axis of the first light beam than the second light detection region.

Alternatively, the second light detecting means has a first light detecting area for detecting light in the first area, and a second light detecting area for detecting light in the second area. It is preferable that the first light detection area and the second light detection area share a part thereof.

Further, the condensing optical system includes a spherical aberration correcting means for changing a spherical aberration of light condensed on the information storage medium, and the spherical aberration correcting means receives a signal from the spherical aberration detecting means. It preferably works.

In the first optical head device, the information storage medium has a track of a specific pitch, and the branching means sets an area where the + 1st order light and the 0th order light diffracted by the track overlap with an inner area + 1A. And the outer area + 1B surrounding the area + 1A
And a region where the -1st-order light and the 0th-order light diffracted by the track overlap each other, is branched into four regions: an inner region -1A and an outer region -1B surrounding the region -1A, and the light amount of the region + 1A When the sum signal of the proportional signal and the signal proportional to the light amount of the area -1B is RT +, and the sum signal of the signal proportional to the light amount of the area + 1B and the signal proportional to the light amount of the area -1A is RT- It is preferable to include a tilt detection unit that detects a tilt amount of the information storage medium and the focusing optical system in the track direction based on a difference signal between the signal RT + and the signal RT−.

In order to achieve the above object, a second optical head device according to the present invention includes a light source for emitting light, and a light condensing means for condensing light emitted from the light source onto an information storage medium. A condensing optical system, branching means for branching the return light reflected by the information storage medium into light in a first area near the optical axis and light in a second area far from the optical axis, A light detecting means for receiving light, wherein light condensed on the information storage medium by using a difference between a defocus amount of light in the first region and a defocus amount of light in the second region. When detecting the amount of spherical aberration of
When the relative distance between the information storage medium and the light collecting means changes,
It is characterized in that the defocus amount of light in the first area and the change amount of defocus amount of light in the second area are equal.

In the second optical head device, the cross section of the light used in the condensing optical system is a substantially circular shape having a first radius Rb, and is concentric with the substantially circular shape and smaller than the first radius Rb. A circular area having a radius R1 of 2 is defined as a first area,
A region outside the region and inside a substantially circle of the first radius Rb is defined as a second region. When the relative distance between the information storage medium and the light condensing means changes, the focal point of light in the first region is changed. It is preferable that the ratio between the first radius Rb and the second radius R1 is determined so that the shift amount and the change amount of the defocus amount of light in the second area become equal.

In order to achieve the above object, a third optical head device according to the present invention comprises a light source for emitting light, a sub-beam generating means for generating a sub-beam from light emitted from the light source, a sub-beam and a sub-beam other than the sub-beam. A condensing optical system including a condensing means for condensing the main beam onto the information storage medium; and a first light having a large light amount and the first light having a large amount of light reflected by the information storage medium. Branching means for splitting the second light into a second light having a smaller light amount than that of the second light, and splitting the second light into light in a first area near the optical axis and light in a second area far from the optical axis; A first light detecting means for receiving the first light and outputting a signal for reproducing information recorded on the information storage medium; and a light receiving the second light and condensed on the information storage medium. Second light detecting means for outputting a signal for detecting the aberration of light, and information Third light detecting means for detecting a return sub-beam reflected by the storage medium, wherein the second light detecting means and the third light detecting means are arranged in a direction substantially orthogonal to the first light detecting means. It is characterized by being arranged in.

To achieve the above object, a fourth optical head device according to the present invention includes a light source for emitting light, and a light condensing means for condensing the light emitted from the light source onto an information storage medium. A condensing optical system, branching means for branching the return light reflected by the information storage medium into a first light having a large light quantity and a second light having a small light quantity as compared with the first light, A first light detecting means for receiving a second light and a signal for outputting a signal for reproducing information recorded on the information storage medium;
A second light detecting means for outputting a signal for detecting an aberration of the light condensed on the information storage medium; and a signal from the first light detecting means and a signal from the second light detecting means. Means for judging that the distance between the information storage medium and the light collecting means is within a specific range based on the sum signal.

In order to achieve the above object, a fifth optical head device according to the present invention includes a light source for emitting light and a light condensing means for condensing light emitted from the light source onto an information storage medium. A condensing optical system, branching means for branching the return light reflected by the information storage medium into a first light having a large light quantity and a second light having a small light quantity as compared with the first light, A first light detecting means for receiving a second light and a signal for outputting a signal for reproducing information recorded on the information storage medium;
A second light detecting means for outputting a signal for detecting an aberration of light condensed on the information storage medium, wherein the light amount of the first light is ηm and the light amount of the second light is ηs; The numerical aperture of the optical optical system is NA, the lateral magnification of the return path from the information storage medium of the condensing optical system to the first and second light detecting means is α, the information storage medium has a plurality of reflection surfaces, When the optical distance between the two reflecting surfaces of the storage medium is d and the area of the detection area of the second light detection means is S1, S1 ≦ 4 · π · (d · NA · α) ² · ηs / ηm It is characterized by having the following relationship.

In order to achieve the above object, an information recording / reproducing apparatus according to the present invention comprises a light source for emitting light and a light condensing means for condensing light emitted from the light source onto an information storage medium. The optical system and the return light reflected by the information storage medium
Branching means for branching into a first light having a large light quantity and a second light having a small light quantity as compared with the first light; and receiving the first light;
First light detection means for outputting a signal for reproducing information recorded on the information storage medium, and a second light detection means for receiving the second light and detecting an aberration of the light focused on the information storage medium An optical head device having a second light detecting unit for outputting a signal; a moving unit for relatively moving the optical head device and the information storage medium; and a control unit for controlling the optical head device and the moving unit. It is characterized by the following.

In order to achieve the above object, a method for detecting aberration according to the present invention is directed to a condensing optical system including a light source for emitting light and a condensing means for condensing the light emitted from the light source onto an information storage medium. System, a branching unit for branching the return light reflected by the information storage medium into a first light having a large light amount and a second light having a small light amount as compared with the first light, and receiving the first light And a second light detecting means for receiving the second light, wherein the aberration is recorded on an information storage medium using a signal from the first light detecting means. The reproduced information is reproduced, and the aberration of the light collected on the information storage medium is detected using the light from the second light detecting means.

In order to achieve the above object, a method for adjusting an optical head device according to the present invention includes a light source for emitting light, and a light condensing means for condensing light emitted from the light source onto an information storage medium. A condensing optical system, branching means for branching the return light reflected by the information storage medium into light in a first area close to the optical axis and light in a second area far from the optical axis, And a photodetector having a first photodetection area for detecting light in the first area and a second photodetection area for detecting light in the second area. An adjustment method for an optical head device, wherein a first light detection area and a second detection area are divided by a division line substantially parallel to a straight line passing through the center of the optical axis of each light, and The detection region is divided into a region 1A and a region 1B by a division line, and the second light detection region is divided by a division line. Is divided into a region 2A on the same side as the region 1A and a region 2B on the same side as the region 1B with respect to the dividing line, and the sum signal of the detection signal from the region 1A and the detection signal from the region 2B is S1, and the region 1B S2 is the sum signal of the detection signal by the detection signal from the area 2A and the detection signal by the area 2A.
The branching means is adjusted by using a rotating mechanism so that the difference signal between the sum signal S1 and the sum signal S2 becomes zero.

According to the above arrangement, a spherical aberration detection signal can be stably obtained even on an information recording medium having a high recording density, and information can be stably recorded and reproduced.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to FIGS. In the drawings referred to below, elements denoted by the same reference numerals perform the same operation.

(Embodiment 1) In Embodiment 1, reflected light from an optical disk as an information storage medium is divided into an inner beam and an outer beam by a hologram element. A method for obtaining a spherical aberration error signal and obtaining an information reproduction signal from the zero-order light will be described.

FIG. 1 is a configuration diagram of an optical head device according to Embodiment 1 of the present invention. In FIG. 1, light emitted from a semiconductor laser 101 as a light source is converted into parallel light by a collimator lens 102 and passes through a diffraction grating 112 as a sub-beam generating unit. At this time, the diffraction grating 112
Generates ± first-order diffracted light, and the light is split into three beams. Of the three beams, the beam based on the 0th-order diffracted light at the center is called a main beam, and the beams on both sides by the ± 1st-order diffracted lights are called sub-beams. The three beams pass through the beam splitter 103. The transmitted three beams have their wavefronts converted by a lens set 104 of a concave lens and a convex lens as a spherical aberration correcting means, and an optical disk 1 as an information storage medium by an objective lens 105 as a condensing means.
07. Main beam is optical disk 107
When over a certain track above, the two sub-beams are positioned to be halfway between that track and an adjacent track. The three focused beams are
The light is reflected and diffracted by the track on the reference numeral 07, passes through the objective lens 105 and the lens set 104 again, and is reflected by the beam splitter 103.

The description of FIG. 1 will be continued. The three beams reflected by the beam splitter 103 are split into diffracted light and zero-order light by a hologram element 108 as a splitting unit. The three beams, which are the zero-order light passing through the hologram element 108, are collected by the detection lens 109,
The astigmatism in the direction of 45 degrees is given to the track by the cylindrical lens 110, and the light detector 1 as the light detecting means is provided.
Enter 11. The signal output from the photodetector 111 in response to the light is an RF signal / FE signal / TE signal generation circuit 2
01 is input. The RF signal output from the RF signal / FE signal / TE signal generation circuit 201 is
7, the focus error (FE) signal and the track error (TE) signal are
It is input to the control / drive circuit 204. Control / drive circuit 2
04 receives the FE signal and the TE signal,
5 is driven.

On the other hand, the + 1st order light and the -1st order light of the main beam diffracted by the hologram element 108 are also detected by the detection lens 109.
Then, the astigmatism in the direction of 45 degrees is given to the track by the cylindrical lens 110 and the light enters the photodetector 111. A signal output from the photodetector 111 in response to these lights is input to the SAE signal generation circuit 202. S
The AE signal generation circuit 202 outputs a spherical aberration error signal (SAE signal). The SAE signal is supplied to the control / drive circuit 203.
The control is performed such that the distance between the lenses of the lens set 104 as the spherical aberration correcting means is changed, and the spherical aberration of the beam on the optical disk 107 is minimized. The hologram element 108 and the SAE signal generation circuit 202 constitute a spherical aberration detecting unit.

FIG. 2 is a front view of the hologram element 108. Diffraction gratings with different grating intervals are formed in a region 1200 outside the circle with the radius R1 and a region 1201 inside the circle with the radius R1. Optical disk 107
The projection on the hologram element 108 of the beam reflected and diffracted by the optical lens 105 and passed through the objective lens 105 corresponds to a circle having a radius Rb (a circle shown by a broken line in the figure). R1 / Rb is about 0.75. As a result, the area of the beam on the outer region is substantially equal to the area of the beam on the inner region, and the signal intensity is also substantially equal. At this time, the optical disk 107
The detection sensitivity, which is the degree of change of the SAE signal with respect to the spherical aberration due to the thickness error or the like, becomes highest. Therefore, R1
The optimum value of / Rb is around 0.75. FIG. 5 is a diagram in which the fluctuation of the SAE signal value due to defocus is plotted using R1 / Rb as a parameter. From this FIG.
It can be seen that the fluctuation of the SAE signal value due to defocus is small when 1 / Rb is about 0.75. In order to reduce the variation of the SAE signal due to defocus, a change in the defocus amount, which is a change in the relative distance between the optical disk 107 as the information storage medium and the objective lens 105 as the light condensing means, occurs in the first region. The amount of change in the amount of defocus of light included in a certain region 1200 and the amount of change in the
It is only necessary that the amount of change in the amount of defocus of the light included in 1 is equal. When the SAE signal value fluctuates due to defocus, the servo loop of the focus control and the servo loop of the spherical aberration correction control interfere with each other, causing a problem that the control is not stable. If R1 / Rb is around 0.75, this interference is small and stable control is possible. The optimum value of R1 / Rb depends on the light intensity ratio between the center and the end of the beam. When the ratio of the light intensity at the end to the light intensity at the center is small, the smaller R1 / Rb, the smaller the interference.

FIG. 3 shows the arrangement of the detection area of the photodetector 111, the RF signal / TE signal / FE signal generation circuits 201 and S
FIG. 3 is a detailed configuration diagram of an AE signal generation circuit 202 and the like. FIG.
, The photodetector 111 includes a main beam detection region (regions 153a to 153d), a sub beam detection region (regions 152a to 153d, and regions 154a to 154d), S
AE signal detection area (areas 151a to 151f, area 15
5a to 155f) are roughly divided into three detection areas. The 0th-order light transmitted through the hologram element 108 in the main beam is the beam 121, the 0th-order light transmitted through the hologram element 108 in the sub-beams is the beams 124a and 124b, and the hologram element 1 in the main beam.
The beam of the +1 order light diffracted in the region 1200 of 08 is 1
22a, the −1st-order light beam is 122b, the + 1st-order light beam diffracted in the region 1201 is 123a, and the −1st-order light beam is 123b.

The detection areas 153a to 153d correspond to the beam 1
21 and outputs a current signal corresponding to the amount of received light. The current-voltage conversion circuit 211 receives the current signal and outputs a voltage signal. The adder 228 includes detection areas 153a and 153c arranged diagonally among the detection areas of up, down, left, and right.
Are added. The adder 229 adds up the signals output from the detection areas 153b and 153d arranged at different diagonals among the upper, lower, left, and right detection areas. Differential circuit 230 receives the signal output from adder 228 and the signal output from adder 229, and outputs the difference signal. This is the focus error signal (FE). The phase difference TE generation circuit 231 includes an adder 228 and an adder 22.
9, and outputs a phase difference tracking error signal (TE) by comparing the phases.

The adder 232 adds the signals output from the detection areas 153a and 153b arranged on the left side among the upper, lower, left and right detection areas. The adder 233 includes a detection area 153c arranged on the right side among the upper, lower, left, and right detection areas.
And the signal output from 153d. Differential circuit 2
34 is a signal output from the adder 232 and the adder 23
3 and outputs the difference signal.
This is a push-pull TE signal (PP-TE). The adder 235 receives the output signals from the adders 232 and 233 and outputs the sum signal. This is an RF for reproducing information recorded on the optical disc 107.
Signal.

The detection areas 152a to 152b and the detection areas 154a to 154b respectively
4a and 124b, and outputs a current signal corresponding to the amount of light received. Current-voltage conversion circuit 210 receives the current signal and outputs a voltage signal. Differential circuit 236 receives the sum signal of the output signals from detection region 152a and detection region 154a, and the sum signal of the output signals from detection region 152b and detection region 154b, and outputs the difference signal. This is a sub-beam TE signal (SUB-TE). The differential circuit 237 receives output signals from the differential circuits 234 and 236 and outputs the difference signal. This is the differential push-pull (DPP) TE signal (DP
P-TE). Adders 228, 229, 232, 2
33, 235 and differential circuits 230, 234, 236, 2
37 and the phase difference TE generation circuit 231 to generate the RF signal F
An E signal / TE signal generation circuit 201 is configured.

The description of FIG. 3 will be continued. Detection area 151
a to 151f receive the beams 122a and 123a, and output current signals corresponding to the amount of received light. The detection areas 155a to 155f receive the beams 122b and 123b,
A current signal corresponding to the amount of received light is output. Current-voltage conversion circuit 210 receives the current signal and outputs a voltage signal. The adder 221 includes detection areas 151b, 151d, 1
51f and detection areas 155a, 155c, 155e
Are added. The adder 222
Adds the signals output from the detection areas 151a, 151c, 151e and the detection areas 155b, 155d, 155f. Differential circuit 223 receives the signal output from adder 221 and the signal output from adder 222, and outputs the difference signal. This is a spherical aberration error signal (SAE signal). Two adders 221, 222
And the differential circuit 223 constitute the SAE signal generation circuit 202.

On the other hand, the adder 224 outputs the detection area 151.
a, 151b, 151c, and the detection areas 155d, 1
The signals output from 55e and 155f are added. Further, the adder 225 outputs the detection areas 151d, 151e, 1
51f and detection areas 155a, 155b, 155c
Are added. Differential circuit 226 receives the signal output from adder 224 and the signal output from adder 225, and outputs the difference signal. This is because beams 122a, 122b and beams 123a, 12
3b, and a rotation error signal (ROT) representing a rotation shift between the detection regions 151a to 151f and the detection regions 155a to 155f, respectively. The ROT signal is used to adjust the angle in the rotation direction between the hologram element 108 that generates a beam for spherical aberration and the photodetector 111 during head adjustment. The hologram element 108 includes a rotation adjusting mechanism 212
(FIG. 1). Rotation adjustment mechanism 212
R is an output signal from the ROT signal generation circuit 251.
Upon receiving the OT signal, the hologram element 108 is rotated and adjusted so that the value of the ROT signal becomes zero. Thereby, the hologram element 108 is set at a correct position with respect to the photodetector 111.

FIG. 4A is a configuration diagram of the current-voltage conversion circuit 210. Each of the light detection areas 151a to 151f, 152
a, 152b, 154a, 154b, 155a-155
A reverse bias voltage Vc is applied to f. The current signal Ip1 output from each of the light detection areas flows to the conversion resistor 242 having the resistance value R1. Conversion resistor 242
Causes a voltage drop of Ip1 × R1. This voltage drop is output to the subsequent circuit by the voltage follower constituted by the operational amplifier 243. Since this configuration does not amplify the low-frequency 1 / f noise generated by the operational amplifier, it is suitable for a low-frequency signal current-voltage conversion circuit.

FIG. 4B is a configuration diagram of another current / voltage conversion circuit 211. In each of the light detection areas 153a to 153d,
Reverse bias voltage Vc is applied. The current signal Ip2 output from each of these light detection regions flows into the conversion resistor 244 having the resistance value R2. The conversion resistor 244 also serves as a feedback resistor of the operational amplifier 246. Operational amplifier 246
Is a reference voltage via the resistor 245, a voltage of −Ip2 × R2 with respect to the reference voltage is output to the subsequent circuit as an output signal of the operational amplifier 246. This configuration is suitable for a high-frequency signal current-voltage conversion circuit even if a large conversion resistor is used because it is separated from a stray capacitance such as a photodetection region.

Next, the distribution ratio of the light quantity of each beam will be described. In the configuration of the present embodiment, the high frequency (Equation 10)
MHz) is applied to the central detection area 1
Only signals output from 53a to 153d. Detection areas 151a to 151f, detection areas 155a to 155f
Is output from the optical disc at a rotational speed of 10 to detect the spherical aberration and drive the spherical aberration correcting means.
A frequency of about twice (about several hundred Hz) is used. Therefore, the beam 121 of the 0th-order diffracted light of the hologram 108
In comparison with the above, the light amounts of the ± 1st-order diffracted light beams 122a and 122b and the beams 123a and 123b can be reduced, and the light amount of the 0th-order light can be increased accordingly. In a recordable optical disk, the reflectance of the recording layer is lower than that of a read-only optical disk, and in a multilayered optical disk for increasing the recording capacity, the substantial reflectance is further reduced. On the other hand, in order to reproduce a small amount of light with a high signal-to-noise ratio (SN ratio), the conversion resistance of the current-voltage conversion circuit may be increased, but if the conversion resistance is increased, the conversion resistance and the light detection area There is a problem that a high-frequency signal cannot be obtained due to the low-pass filter formed between the floating capacitor and the stray capacitance. In addition, when several signals are added to obtain an RF signal, noise generated in the current-voltage conversion circuit is added together, which causes a reduction in the SN ratio. Considering these, in order to reproduce the RF signal, it is necessary to allocate as much light as possible and reduce the number of current-voltage conversion circuits, and this embodiment satisfies this requirement.

As a method for detecting spherical aberration caused by an error in the thickness of the base material of the protective layer, for example, Japanese Patent Laid-Open No. 2000-18
Japanese Patent Application Laid-Open No. 2254 discloses a method (spot size method) in which light in a region near the optical axis is separated by a hologram element, and defocus is detected from the size of a spot. Japanese Patent Application Laid-Open No. 2000-171346 discloses that a semi-circular region near the optical axis and a semi-circular region far from the optical axis by a hologram element are separated, and defocusing is performed using the fact that the directions of the semicircles are switched before and after the focal point. (Knife edge method) is described.

However, in each method, since the entire light beam is divided into several parts, it is necessary to add signals obtained from these separate detection areas to the information reproduction signal. For this reason, the number of operational amplifiers in the current-voltage conversion circuit increases, and the SN ratio of the reproduced signal decreases. That is,
In Japanese Patent Application Laid-Open No. 2000-182254, the number of operational amplifiers doubles, so that the SN ratio deteriorates about 0.71 times. In Japanese Patent Application Laid-Open No. 2000-171346, the number of operational amplifiers increases from three to five. Therefore, the SN ratio deteriorates 0.77 times. Therefore, the error rate of information reproduction increases. In the present embodiment, the diffraction grating of the hologram element can be freely designed, and the distribution ratio of the zero-order light can be set to 80% or more. For this reason, it is possible to detect spherical aberration while keeping the S / N ratio from decreasing 0.8 times or more.

In the example of this embodiment, due to spherical aberration,
The beams 123a and 123b, which are light on the inner circumference, and the beams 122a, 122b, which are light on the outer circumference, are distorted in directions different by 90 degrees. This distortion is caused by the cylindrical lens 110
The principle that the direction in which the beam is distorted differs depending on the relationship between the photodetector and the position of the focal point is also used as the focus error detection in the astigmatism method. Based on this principle and the arrangement of the beams, the output signals from the detection regions arranged in a zigzag manner are added to the detection regions 151a to 151f and 155a to 155f, and the difference signal is obtained, thereby obtaining the beam 12.
3a and 123b and the beams 122a and 122
The difference between the defocus amounts b is obtained, and a spherical aberration error signal can be obtained. By controlling the lens interval of the lens set 104 as the spherical aberration correcting means by this signal,
The spherical aberration of the spot is kept small, information can be recorded and reproduced stably, and the error rate can be kept low.

Here, the beams 123a, 123
The amount of spherical aberration was determined from the difference between the defocus amount of b and the defocus amounts of the beams 122a and 122b.
123b alone or the beams 122a,
Even if only the defocus amount of 22b is used, the spherical aberration amount can be detected if the defocus is zero.

In the configuration of the present embodiment, light in the inner peripheral area is directed to the side closer to the optical axis center of the zero-order light, and light in the outer peripheral area is directed to the side farther from the optical axis center. This is because the light in the inner peripheral area has a small spread on the photodetector, and the light in the outer peripheral area has a large spread on the photodetector. The light in the outer peripheral area is located far from the center of the optical axis, which greatly affects the light position fluctuation due to the wavelength fluctuation of the light source and the focal length fluctuation of the detection lens. The light in the inner peripheral region is arranged at a position near the optical axis center where the influence is small. This makes it possible to suppress the deterioration of the characteristics of the spherical aberration signal even if the wavelength of the light source fluctuates or the focal length of the detection lens fluctuates.

When the differential push-pull method (DPP method) and the spherical aberration detection are performed as in this configuration, as shown in FIG. 3, the sub-beam and the spherical surface to which the DPP method is applied are arranged on the photodetector. The light beam for detecting aberration is
It is arranged in a direction substantially orthogonal to the zero-order light of the main beam. Thus, interference between the sub-beam to which the DPP method is applied and the light beam for detecting spherical aberration can be minimized. Here, an example is shown in which the sub-beams are used for the DPP method. However, even if the sub-beams are used for tracking in the three-beam method, an effect of minimizing interference can be obtained by using this arrangement.

Further, when the light in the inner peripheral area and the light in the outer peripheral area are detected side by side as in this configuration, two lights outside the detection area for detecting the light in the inner peripheral area and the light in the outer peripheral area are detected. The two inside the detection area can be shared.
Thus, the detection area can be reduced, and the detection area can be simplified and downsized. As a result, the size of the optical head device can be reduced.

Next, instead of the hologram element 108,
A method of using the hologram element 301 shown in FIG. 6 to also perform radial tilt detection will be described.
In the hologram element 301, regions 1202 to 1205 are provided in accordance with two regions of the main beam where ± 1st-order diffracted light diffracted by the track of the optical disk 107 overlaps the original 0th-order light beam, and passes therethrough. Part of the light is diffracted to different places. The region 1202 is located inside the region 1203, and the region 1204 is located inside the region 1205.

FIG. 7 shows the positions of the light diffracted in these regions on the detector. The diffracted light in the region 1202 is light beams 126a and 126b, the diffracted light in the region 1203 is light beams 127a and 127b, the diffracted light in the region 1204 is light beams 128a and 128b, and the diffracted light in the region 1205 is light beams 125a and 125b. By the signal operation, the sum signal RT1 of the output signals from the four detection areas = signal (151a) + signal (151f) + signal (155c)
+ Signal (155d) and the sum signal RT2 of the output signals from the other four detection areas = signal (151b) + signal (151)
e) + signal (155b) + signal (155e). Then, the radial tilt error signal RTE is RT1
And RT2.

If there is a radial tilt, the wavefront becomes N-shaped. ± 1 diffracted by the track of the optical disc 107
When the next-order light overlaps and interferes with the 0th-order light, in the interference region between the + 1st-order light and the 0th-order light, for example, if there is a positive radial tilt,
The light intensity near the center increases and the light intensity near the periphery decreases. Conversely, if there is a negative radial tilt, the light intensity near the center decreases and the light intensity near the periphery increases. On the other hand, -1
In the interference region between the next-order light and the zero-order light, for example, if there is a positive radial tilt, the light intensity near the center decreases and the light intensity near the periphery increases. Conversely, if there is a negative radial tilt,
The light intensity near the center increases and the light intensity near the periphery decreases. Therefore, the sum signal of the output signal from the vicinity of the center of the + 1st-order interference area and the output signal from the periphery of the −1st-order interference area, and the output signal from the periphery of the + 1st-order interference area The radial tilt including the polarity can be detected by calculating the difference between the sum and the output signal from the vicinity of the center of the interference area on the −1st side. By performing tilt correction based on this radial tilt error signal, the coma of the spot is kept small, information can be recorded and reproduced stably, and the error rate can be suppressed low.

In this embodiment, the detection area 1
51a to 151f and detection areas 155a to 155f
And the output signals from the detection areas 153a to 153d, and thereby the optical disc 107 and the objective lens 105 are added.
Can be obtained, which detects that the distance of the target has approached a specific distance near the just focus. The approach detection can be performed only from the sum signal of the output signals from the detection areas 153a to 153d (main PD). However, when the vertical magnification of the detection system is high, the rate of change of the signal is fast, and reliable detection is possible. Can not. Therefore, the sum signal from the main PD and the detection areas 151a to 151 for detecting spherical aberration are used.
f, 155a to 155f (PD for SAE = SAE_P
By adding the output signal from D) with the sum signal,
The ratio of the signal change to the defocus is reduced, and the detection can be reliably performed. Although not shown, the approach detection judging means compares the sum signal with a predetermined detection level, and judges the approach based on the polarity of the difference. This is usually performed in a controller such as a control microcomputer.

FIG. 8 shows how signals change due to defocusing in the above two cases. As shown in FIG. 8, when the sum with the PD for SAE is obtained, the range of the signal is about three times that in the case of only the main PD. Therefore, the approach detection can be reliably performed. Optical disk 1
Even when the objective lens 105 is brought close to the optical disc 107 when focusing on 07, it is possible to reliably detect that the objective lens 105 has come close to the optical disc 107. Therefore, the objective lens 105 collides with the optical disc 107, The possibility of damaging the optical disc 107 is reduced.

When a two-layer disc having two layers on which information is recorded is considered as the optical disc 107, focus control is performed so that light emitted from the objective lens 105 is focused on one of the layers. Sometimes, some light is reflected by the other layer. The light reflected by the other layer is detected as a defocused and spread beam on the detector. The situation at this time is shown in FIG. FIG. 9 shows only a state where the reflected light of the 0th-order light of the main beam on the other layer is defocused. Actually, other light beams corresponding to the sub-beams and the ± first-order light beams of the main beam are detected in a defocused state. However, since the light amount is smaller than that of the 0th-order light beam of the main beam, here, Attention is paid only to the zero-order light.

The spread of the 0th-order light of the main beam on the other layer in the other layer is substantially circular, the radius Rs is the optical distance d between the two layers of the disk, the information storage of the condensing optical system. Assuming that the numerical aperture on the medium side is NA and the flattening rate of the return path from the focusing optical system to the photodetector is α, Rs = 2 · d · NA
Is represented by α. The light reflected by the other layer has uneven light quantity depending on the location, and when this light changes its position on the photodetector due to lens shift, disc tilt, or the like,
An error is given to the spherical aberration error signal. This uneven light amount is about several percent of the total light amount. If the amount of light reflected by the other layer is substantially the same as the amount of light for the original detection, the effect on the spherical aberration error signal is about several percent.
Therefore, when the area of the detection area of the photodetector for obtaining the spherical aberration error signal is S1 (= 2PDxPDy), S1 ≦ π · Rs · Rs · ηs / ηm, ie, S1 ≦ 4 · π · ( d · NA · α) ² · ηs / ηm Here, ηs is the amount of light used for detecting spherical aberration, and ηm is the amount of zero-order light of the main beam. In an optical system in which this relational expression holds, even if there is reflected light from the other layer, the error of the spherical aberration error signal is small,
Information can be read and recorded correctly.

Although two layers are considered here, the same effect can be obtained when three or more layers are used.

In this embodiment, as a method for obtaining the defocus amount of the diffracted beam, the FE by the astigmatism method is used.
Although the signal generation is used, a spot size method or a knife edge method may be used. In that case, the shape of the spot is distorted due to the influence of the cylindrical lens that gives astigmatism, but the shape of the detection area is designed according to the distortion, or the cylindrical lens is made by giving astigmatism to the diffracted light by the hologram element. Cancels astigmatism generated by In addition, if a focus error detection method other than the astigmatism method is used, spherical aberration detection using a spot size method, a single knife edge method, a double knife edge method, or the like is performed without concern for spot shape distortion. be able to.

Although the position where the hologram element 108 is disposed is located in front of the detection lens 109, the position is not limited to this position. It may be between the detection lens 109 and the cylindrical lens 110 or between the cylindrical lens 110 and the photodetector 111. FIG. 10 shows that the hologram element 113 is connected to the cylindrical lens 11.
2 shows a configuration in the case where the photodetector 111 is disposed between the photodetector 111 and the photodetector 111.
The light beam is split by the hologram element 113 into light in an inner peripheral region and light in an outer peripheral region. In this case, as shown in FIG. 11, the divided shape of the hologram element 113 is preferably an elliptical shape. This is because the light beam is distorted into an elliptical shape by the cylindrical lens 110. According to this oval,
The dividing line separating the outer peripheral area 1206 and the inner peripheral area 1207 is also made elliptical. If the major axis radius of the beam on the hologram element 113 is RbL, the minor axis radius is RbS, the major axis radius of the ellipse of the dividing line is R1L, and the minor axis radius is R1S, then R1
The detection sensitivity is highest when L = 0.75 × RbL and R1S = 0.75 × RbS, and no error occurs in spherical aberration detection even if defocus occurs. In this configuration, even if the focal length f of the detection lens 109 varies, the positional relationship between the spot for detecting spherical aberration and the detection area of the photodetector 111 does not shift, so that a spherical aberration signal can be stably obtained.

FIG. 12 is a schematic diagram showing the configuration of an optical disk drive as an optical information recording / reproducing apparatus. The optical disk 107 is fixed and rotated by a clamper 602 to a motor 601 as moving means. The optical head device 604 described in the present embodiment is moved in the radial direction of the disk by a traverse 603 as moving means. The control circuit 605 outputs on / off signals for driving, focus control, and tracking control of laser to the optical head device 604, and receives an RF signal,
Play information. Further, the control circuit 605 includes the motor 6
A control signal is also sent to the traverse 603 and the traverse 603 to control them. Thereby, information can be recorded or reproduced at an arbitrary position on the optical disc 107 as an optical information storage medium.

In the present embodiment, the spherical aberration is corrected by converting the wavefront by the lens set. However, the spherical aberration may be corrected by using a liquid crystal or the like. In this case, the spherical aberration in the forward path may be corrected, but the spherical aberration in the backward path may not be corrected. Even if light having no aberration is collected on the optical disc 107, the spherical aberration error signal does not become zero. . Also in this case, the amount of spherical aberration corrected based on the signal driving the liquid crystal or the like can be known. By subtracting a signal obtained by multiplying the corrected spherical aberration amount by a coefficient from the spherical aberration error signal and performing control so that the difference becomes zero, a spot having no aberration on the information layer of the optical disk 107 can be obtained. .

In this embodiment, the differential push-pull method (DPP method) and the phase difference method are assumed as the tracking control. However, a combination of the ordinary push-pull method and the three-beam method may be used. Although an optical disk is assumed as the information storage medium, the same effect can be obtained with an optical card or the like.

(Embodiment 2) In this embodiment, a case will be described in which a hologram element as a branching means for branching light for detecting spherical aberration is blazed.
FIG. 13 shows the configuration of this optical system. This configuration is almost the same as that of the first embodiment, except that another hologram element 114 is used instead of the hologram element 108, and the photodetector 11
Instead of 1, another photodetector 115 is used.

The signal output from the photodetector 115 is 2
FE signal generation circuits 205 and 209. S
The AE signal generation circuit 202 includes two FE signal generation circuits 2
Receiving the signals output from the signals 05 and 209, the difference signal is calculated and output as a spherical aberration error signal (SAE signal).

FIG. 14 shows a front view of the hologram element 114. A diffraction grating blazed so that light is diffracted in the + Y direction in the figure is produced in a region 1208 outside the circle with the radius R1, and a region 1209 inside the circle with the radius R1 is in the -Y direction in the diagram. A diffraction grating blazed so that light is diffracted is manufactured. The projection of the beam reflected / diffracted by the optical disk 107 and passed through the objective lens 105 onto the hologram element 114 is a circle having a radius Rb (a broken-line circle in the figure). When R1 / Rb is about 0.75, the spherical aberration detection sensitivity is the highest, and no error occurs in the spherical aberration detection even if defocus occurs.

FIG. 15 shows an example of the arrangement of the detection area of the photodetector 115 and a detailed configuration example of the FE signal generation circuit 205 and the like.
In FIG. 15, a photodetector 115 receives a light beam for detecting spherical aberration by two upper, lower, left, and right detection areas.
The zero-order light transmitted through the hologram element 114 is the beam 12
2. The + 1st-order light beam diffracted in the area 1208 of the hologram element 114 is 129a, and the -1st-order light beam diffracted in the area 1209 is 129b. Detection area 1
56a to 156d receive the beam 129a and output a current signal corresponding to the amount of received light. Current-voltage conversion circuit 2
10 receives this current signal and outputs a voltage signal. On the other hand, the detection areas 157a to 157d receive the beam 129b and output a current signal corresponding to the amount of received light. The current-voltage conversion circuit 210 receives this current signal and outputs a voltage signal.

The adder 240 outputs the detection areas 156a and 156a.
6c is added. On the other hand, the adder 241
Add output signals from the detection areas 156b and 156d. Differential circuit 242 receives the output signal from adder 240 and the output signal from adder 241 and outputs the difference signal. This is the FE signal in the outer peripheral area. The adders 240 and 241 and the differential circuit 242 constitute the FE signal generation circuit 205.

Further, the adder 243 detects the detection area 157.
a, 157c are added. On the other hand, the adder 244 adds the output signals from the detection areas 157b and 157d. Differential circuit 245 receives the output signal from adder 243 and the output signal from adder 244, and outputs the difference signal. This is the FE signal in the inner peripheral area.
Another FE signal generation circuit 209 includes the adders 243 and 244 and the differential circuit 245. Differential circuit 2
23 is an output signal from the differential circuit 242 and the differential circuit 24
5 and outputs the difference signal. This is a spherical aberration error signal (SAE signal). The differential circuit 223 forms the SAE signal generation circuit 202.

The adder 224 includes detection areas 156a, 156
6b, the output signals from the detection areas 157c and 157d are added. Further, the adder 225 outputs the detection areas 156c, 1
56d, the output signals from the detection areas 157a and 157b are added. Differential circuit 226 receives the output signal from adder 224 and the output signal from adder 225, and outputs the difference signal. This is because the beam 129a and the detection area 15
6a to 156d, beam 129b and detection area 157a to
A rotation error signal (ROT signal) representing a rotation deviation from 157d. The ROT signal includes a hologram element 114 for generating a beam for spherical aberration during head adjustment and a photodetector 11.
5 is used to adjust the angle in the rotation direction.

In the present embodiment, due to the spherical aberration, the inner beam light 129b and the outer light beam 12b
The beam is distorted in a direction different from that of 9a by 90 degrees. This distortion is due to astigmatism given by the cylindrical lens 110, and the principle that the direction in which the beam is distorted differs depending on the relationship between the photodetector and the focal point position is also used as focus error detection in the astigmatism method. Is what is done. Based on this principle and the arrangement of beams, the spherical aberration error signal can be obtained by adding the detection areas arranged at diagonal positions to the detection areas 156 and 157 and obtaining the difference signal. By controlling the spherical aberration correcting means 104 based on the spherical aberration error signal, the spherical aberration of the spot can be kept small, information can be recorded and reproduced stably, and the error rate can be suppressed low.

Further, according to the configuration of the present embodiment, the range of the detection area of the photodetector can be reduced and simplified, and the optical head device can be reduced in size.

When information is recorded or reproduced on a dual-layer disc or the like, the influence of light reflected on the other information layer different from the target information layer is reduced.

In the present embodiment, the output signal from the differential circuit 242 and the differential circuit 245 are output by the differential circuit 223.
Although the subtraction is performed directly when subtracting the output signal from the control unit, the amplitude balance of one of the output signals may be adjusted through a variable gain amplifier. In this case, since the balance of the spherical aberration error signal can be adjusted, the spherical aberration correction control operates stably.

Further, in the present embodiment, after the FE signal is separately generated in the inner peripheral area and the outer peripheral area, S
The AE signal was obtained, and the sum signal (156a + 156c) of the output signals from the diagonal positions of the detection area 156 and the detection area 1
57 (157b)
+ 157d) and the sum signal (157a +) of the output signal from the diagonal position of the detection area 157.
157c) and the sum signal (156b + 156d) of the output signal from the opposite diagonal position of the detection area 156 are calculated, and the sum signal SAE2 is calculated. From the difference between SAE1 and SAE2,
The spherical aberration error signal SAE may be calculated. According to this configuration, the circuit can be simplified.

In this embodiment, similarly to the first embodiment, the spot by the DPP type sub-beam and the SAE
By arranging the use spots in a direction substantially orthogonal to the zero-order light of the main beam, mutual interference can be reduced. (Embodiment 3) Next, as Embodiment 3, a configuration in which light in an inner peripheral region and light in an outer peripheral region are obliquely directed will be described. FIG. 16 shows the configuration of this optical system. This configuration is almost the same as that of the first embodiment, except that another hologram element 116 is used instead of the hologram element 108, and the photodetector 111
Is replaced by another photodetector 117.

FIG. 17 shows a front view of the hologram element 116. Light incident on the outer region 1210 of the circle having the radius R1 is diffracted in the + Yo direction and the -Yo direction. On the other hand, the light incident on the inner area 1211 of the circle having the radius R1 is + Yi
Diffracted in the −Yi and −Yi directions. The projection of the beam reflected and diffracted by the optical disc 107 and passed through the objective lens 105 onto the hologram element 116 is a circle having a radius Rb (a circle indicated by a broken line in the figure). When R1 / Rb is about 0.75, the spherical aberration detection sensitivity is the highest, and no error occurs in the spherical aberration detection even if defocus occurs.

FIG. 18 shows the arrangement of the detection areas of the photodetector when the hologram element 116 is used. Note that DPP
The sub-beam detection area is omitted. In FIG. 18, the beam 121 of the zero-order light that is not diffracted by the hologram element 116 is received by the central detection areas 153a to 153d. The signal obtained from this beam is handled in the same manner as in the case of FIG. 3 referred to in the first embodiment. Of the beams diffracted by the outer region 1210 of the hologram element 116, the diffracted light in the + Yo direction becomes the beam 132a, and-
The diffracted light in the Yo direction becomes a beam 132b. These beams 132a and 132b are respectively applied to the detection area 172a.
To 172d and 173a to 173d. Here, the four detection areas 172a, 172c, 173a, 1
A signal obtained by adding a signal corresponding to the light received at 73c,
The other four detection areas 172b, 172d, 173b, 1
The difference signal from the signal obtained by adding the signal corresponding to the light received at 73d is defined as SAEo.

On the other hand, the inner region 1 of the hologram element 116
Of the beams diffracted at 211, the diffracted light in the + Yi direction becomes beam 131a, and the diffracted light in the -Yi direction becomes beam 131b. These beams 131a, 131b
Are the detection areas 171a to 171d and 174a to 171d, respectively.
The light is received at 174d. Here, the four detection areas 171
a, 171c, 174a, and a signal obtained by adding signals according to the light received by 174c and the other four detection areas 171
b, 171d, 174b, and a difference signal from a signal obtained by adding signals according to the lights received at 174d are referred to as SAEi.

As a result, the spherical aberration error signal SAE is
It is obtained by subtracting AEo and SAEi.

In this configuration, since the hologram element 116 may have a symmetrical cross-sectional shape, there is an advantage that the hologram element can be easily manufactured as compared with the blazed hologram element 114 of the second embodiment.

The inner region 1 of the hologram element 116
Since the diffraction angles of 211 and the outer region 1210 are almost equal,
The pitch of the hologram element becomes substantially constant, and the production of the hologram element becomes easy.

(Embodiment 4) In Embodiment 4, reflected light from an optical disk as an information storage medium is divided into an inner beam and an outer beam by a hologram element, and a spherical aberration error is obtained from the diffracted light. A method for obtaining a signal and obtaining an information reproduction signal from the 0th-order light will be described in a case where the method is combined with a spot size method.

FIG. 19 shows a configuration of an optical head device according to Embodiment 4 of the present invention. The description of the same parts as in the first embodiment is omitted. In the configuration of the present embodiment, the hologram element 303 that moves integrally with the objective lens 105 and the actuator 106 is provided. Hologram element 303
Consists of a quarter-wave plate and a polarization hologram, and the light going to the optical disk 107 is not diffracted.
Some of the light returning from 7 is diffracted.

A part of the beam condensed by the detection lens 109 is diffracted by the hologram element 304 and enters the photodetector 305. Upon receiving this light, the photodetector 30
5 are output from the RF signal generation circuit 401 and F
The signal is input to the E signal / TE signal generation circuit 402. The signal output from the RF signal generation circuit 401 is
07 is used to reproduce the information recorded. F
The E signal / TE signal generation circuit 402 generates a focus error (FE) signal and a track error (TE) signal,
It is input to the control / drive circuit 207. Control / drive circuit 2
07 receives the FE signal and the TE signal,
5 is driven.

On the other hand, the + 1st-order light and the -1st-order light diffracted by the hologram element 304 enter the photodetector 305, become electric signals, and are input to arithmetic circuits 403 and 404, respectively. The signals output from the arithmetic circuits 403 and 404 are both input to the differential circuit 405, and the difference signal is generated. This becomes a spherical aberration error (SAE) signal. SA
The E signal is input to the control / drive circuit 206, whereby the distance between the concave lens and the convex lens of the lens set 104 as the spherical aberration correcting means is changed so that the spherical aberration of the beam on the optical disk 107 is minimized. Controlled.

FIG. 20 shows a front view of the hologram element 304. Light incident on the outer region 1212 of the circle having the radius R1 is diffracted in the + Yo direction and the -Yo direction. On the other hand, the light incident on the inner area 1213 of the circle having the radius R1 is + Yi
Diffracted in the −Yi and −Yi directions. The projection of the beam reflected and diffracted by the optical disc 107 and passed through the objective lens 105 onto the hologram element 304 is a circle having a radius Rb (a circle shown by a broken line in the figure). R1 / Rb is about 0.75. At this time, the spherical aberration detection sensitivity is the highest, and no error occurs in the spherical aberration detection even if defocus occurs.

FIG. 21 shows a front view of the photodetector 305 and the arrangement of beams. The beam is divided into four by the hologram element 303, and a beam focused on the front side of the detection surface of the photodetector 305 and a beam focused on the rear side are generated from the respective areas. Hologram element 303,
A beam 351 transmitted through both of them as the zero-order light becomes 351. This beam 351 is detected in the detection area 501,
The output signal therefrom is input to the RF signal generation circuit 401.

The +1 order light diffracted by the hologram element 303 becomes eight beams 352. These beams 35
2 is detected in a detection area 502 composed of eight strip-shaped portions, and an output signal from the detection area 502 is input to an FE signal / TE signal generation circuit 402 to generate a focus error (FE) signal. The focus error signal is obtained by the spot size method.

On the other hand, the minus first-order light diffracted by the hologram element 303 becomes eight beams 353. These beams 353 are detected in a detection area 503 composed of four parts, and an output signal therefrom is input to an FE signal / TE signal generation circuit 405 to generate a track error (TE) signal. The track error signal is obtained by a push-pull method and a phase difference method.

Also, the 0 transmitted through the hologram element 303
Part of the next light is diffracted by the hologram element 304,
The beams become 354, 355, 356, and 357. The beam 354 is a beam diffracted by the outer region 1212 of the hologram element 304 and focuses on the front side of the detection surface of the photodetector 305. The beam 355 is transmitted to the hologram element 3
The light is a beam diffracted in the inner region 1213 of the light source 04 and focuses on the rear side of the detection surface of the photodetector 305. Beam 3
Reference numeral 56 denotes a beam diffracted by the outer region 1212 of the hologram element 304, which focuses on the rear side of the detection surface of the photodetector 305. The beam 357 is applied to the hologram element 30
4 is a beam diffracted by the inner area 1213 and is focused on the front side of the detection surface of the photodetector 305.

The beams 354 and 355 are applied to the detection area 50.
4, 505 and 506, the beams 356 and 357
Are received in the detection areas 507, 508, 509. The output signals from the detection areas 504 to 506 are
3 is calculated, (signal of area 504) + (signal of area 506) − (signal of area 505) is calculated and output. Output signals from the detection areas 507 to 509 are input to the arithmetic circuit 404, and (signal of the area 507) + (area 5)
09) − (signal of area 508) is calculated and output. The differential circuit 405 receives the output signals from the arithmetic circuits 403 and 404 and outputs the difference signal. This difference signal becomes a spherical aberration signal (SAE signal).

In this embodiment, the beam for the focus error signal and the beam for the track error signal are separated from the beam for the RF signal by the hologram element 303 driven integrally with the objective lens 105, and the detection lens 109 and the light detection Vessel 3
05 by the hologram element 304 disposed between
A beam for detecting spherical aberration is generated from the beam for the F signal. In this case, since the RF signal can be detected by one detection region and one amplifier, the RF signal has a high S
Spherical aberration can be detected in another detection area while maintaining the N ratio.

In addition, when combined with the spot size method, if the division direction of the detection area of the photodetector 305 and the track direction of the optical disk 107 are the same, the optical disk 1
When the spot on 07 crosses the track, an error occurs in the SAE signal. For this reason, an arrangement in which the track direction is orthogonal to the direction of the dividing line of the detection area is preferable. On the other hand, when the wavelength of the light source changes or the distance between the hologram element and the photodetector changes, each beam moves radially around the beam 351 which is the zero-order light. For this reason, it is preferable to divide the detection region in a substantially radial direction with the beam 351 as a center.

In FIG. 21, in order to solve the above two problems, the division direction of the detection area is kept substantially radially with the beam 351 as the center, and the beams 354 to 357 for detecting spherical aberration are used.
Is provided with astigmatism in the direction of 45 degrees with respect to the track, and on the detection surface, the projection direction of the track of the optical disk and the division direction of the detection area are arranged so as to be orthogonal to each other. The astigmatism in the 45-degree direction is given by the hologram element 304. As a result, even when the spot size method is used, a stable spherical aberration error signal can be obtained even when there is a wavelength fluctuation or crossing a track.

According to the present embodiment, S is used for detecting spherical aberration.
Since the SD (Spot Size Detection) method is used, disturbance at the time of crossing tracks can be reduced, and information can be recorded and reproduced stably.

(Fifth Embodiment) In the fifth embodiment, the reflected light from the optical disk as the information storage medium is divided into an inner beam and an outer beam by a hologram element, and the spherical aberration error signal is obtained from the diffracted light. At the same time, a method for obtaining a track error signal and a focus error signal and obtaining an information reproduction signal from the zero-order light will be described.

FIG. 22 shows a configuration of an optical head device according to Embodiment 5 of the present invention. The description of the same parts as in the first and second embodiments will be omitted. The configuration of the present embodiment includes the hologram element 308 that moves integrally with the objective lens 105 and the actuator 106. Hologram element 30
Numeral 8 includes a quarter-wave plate and a polarization hologram, and the light traveling toward the optical disk 107 is not diffracted.
Some of the light returned from 07 is diffracted. A signal output from the photodetector 309 in response to the light is input to the RF signal generation circuit 401, the TE signal generation circuit 406, the SAE signal generation circuit 407, and the FE signal generation circuit 408.

An output signal from the RF signal generation circuit 401 is used for reproducing information recorded on the optical disk 107. A track error (TE) signal is generated in the TE signal generation circuit 406, a focus error (FE) signal is generated in the FE signal generation circuit 408, and the TE signal and the FE signal are input to the control / drive circuit 207. The control / drive circuit 207 receives the FE signal and the TE signal,
The actuator 106 of the objective lens 105 is driven.

The signal output from the photodetector 309 is also input to the SAE signal generation circuit 407, from which a spherical aberration error (SAE) signal is output. SA
The E signal is input to the control / drive circuit 206, whereby the distance between the concave lens and the convex lens of the assembled lens 104 as the spherical aberration correcting means is changed, and the control is performed so that the spherical aberration of the beam on the optical disk 107 is minimized. Is done.

FIG. 23 shows a front view of the hologram element 308. The light beam has a radius R1 of the hologram element 308.
Circular dividing line 1301 and two cross-shaped dividing lines 13
02 and 1303, the area is divided into eight areas. Although not shown, each region is further divided into two types of regions, from which a front-side focal beam and a rear-side focal beam are generated. The objective lens 10 reflected and diffracted by the optical disc 107
The projection of the beam that has passed through 5 onto the hologram element 308 is a circle having a radius Rb (the circle indicated by the broken line in the figure). R1 /
Rb is set to about 0.75. At this time, the spherical aberration detection sensitivity is the highest, and no error occurs in the spherical aberration detection even if defocus occurs.

FIG. 24 shows a front view of the photodetector 309 and the arrangement of beams. The beam is divided into eight by the hologram element 308, and a beam focused on the front side of the detection surface of the photodetector 309 and a beam focused on the rear side are generated from the respective regions. The beam transmitted through the hologram element 308 as the zero-order light becomes 371. This beam 3
71 is detected in the detection area 501, and an output signal therefrom is input to the RF signal generation circuit 401.

The + 1st order light diffracted by the hologram element 308 becomes 16 beams 372 and 373. The + 1st-order diffracted light generated in the area inside the circular division line 1301 of the hologram element 308 becomes the beam 372, and the + 1st-order diffracted light generated in the area outside the same becomes the beam 373.
The beam 372 is received by the detection area 512, and Fi + and Fi- signals are generated from the alternately arranged areas. The beam 373 is received by the detection areas 511 and 513, and the Fo + signal and the Fo− signal are generated from the alternately arranged areas.

The -1 order light diffracted by the hologram element 308 becomes 16 beams 374 and 375. The -1st-order diffracted light generated in the area inside the circular division line 1301 of the hologram element 308 becomes a beam 374, and the -1st-order diffracted light generated in the area outside the same becomes a beam 375.
Beam 374 is received at detection areas 515 and 516,
Beam 375 is received at detection areas 514 and 517. The signals output from the corresponding detection areas of the detection areas 514 to 517 are added, and T1, T2, T3, T
Four signals are generated.

FIG. 25 shows a TE signal generation circuit 406, SA
E signal generation circuit 407 and FE signal generation circuit 408
Is shown. The Fi +, Fi-, Fo +, and Fo- signals are converted into voltage signals by four current-to-voltage conversion circuits 210. Here, the current-voltage conversion circuit 210 has the configuration shown in FIG. 4A. Differential circuit 411 receives the Fi + signal and the Fi- signal, and outputs the difference signal. The differential circuit 412 receives the Fo + signal and the Fo− signal, and outputs the difference signal. The differential circuit 413 includes the differential circuits 411 and 4
Upon receiving the twelve output signals, the difference signal is output. This is the SAE signal. The adder 414 includes a differential circuit 411
And 412, and outputs the sum signal.
This is the FE signal. The FE signal generation circuit 408 includes differential circuits 411 and 412 and an adder 414. The SAE signal generation circuit 407 includes the differential circuits 411 and 4
12, 413.

The T1, T2, T3, and T4 signals are converted into voltage signals by four current / voltage conversion circuits 211. Here, the current-voltage conversion circuit 211 has the configuration shown in FIG. 4B. Adder 415 receives the T1 signal and the T3 signal, and outputs the sum signal. Adder 416 receives the T2 signal and the T4 signal, and outputs the sum signal. Phase difference T
The E generation circuit 420 receives the output signals of the adders 415 and 416, compares their phases, and outputs a phase difference TE signal (TEd).
pd).

The adder 417 receives the T3 signal and the T2 signal, and outputs the sum signal. The adder 418
It receives the T1 signal and the T4 signal and outputs the sum signal.
Differential circuit 419 receives the output signals of adders 417 and 418 and outputs the difference signal. The output signal of the differential circuit 419 is a push-pull tracking error signal (TEp
p).

Also in the case of the present embodiment, a spherical aberration error signal can be obtained while maintaining the SN ratio of the RF signal. In this configuration, the spherical aberration and the focus error signal are detected using the same beam. Therefore, the number of optical components such as a hologram element can be reduced,
An optical head device can be manufactured at low cost.

The phase difference TE is used as the track error signal.
Although the example in which the signal (TEdpd) and the push-pull tracking error signal (TEpp) are generated has been described, either one of them may be generated.

(Embodiment 6) In Embodiment 6, the reflected light from an optical disk as an information storage medium is received as it is, and divided into an inner circumference and an outer circumference in a detection area of a photodetector to obtain a spherical aberration error signal. The method is described.

FIG. 26 shows a configuration of an optical head device according to Embodiment 6 of the present invention. The description of the same parts as in the first embodiment and the like is omitted. In FIG. 26, the detection lens 109
A cylindrical lens 110 is provided between the photodetector 311 and the astigmatism in the direction of 45 degrees with respect to the track. The signal output from the photodetector 311 includes an RF signal generation circuit 431, an FE signal / TE signal generation circuit 43
3, and input to the SAE signal generation circuit 432.

FIG. 27 shows a front view of the photodetector 311, the arrangement of beams, and the configuration of peripheral circuits. Photodetector 3
The eleven detection areas are double upper, lower, left and right areas, and eight areas 521, 522, 523, 524, and 52 are provided.
5, 526, 527, and 528. The current signals output from these detection areas are converted into voltage signals by the current-voltage conversion circuit 211. The adder 441 is
Upon receiving the output signals from the detection areas 521 and 523, it outputs the sum signal. Adder 442 receives the output signals from detection areas 522 and 524 and outputs the sum signal. Adder 443 receives the output signals from detection areas 525 and 527 and outputs the sum signal. Adder 444
Receives output signals from the detection areas 526 and 528,
The sum signal is output.

The differential circuit 445 receives the output signals of the adders 441 and 442 and outputs the difference signal. Differential circuit 446 receives the output signals of adders 443 and 444 and outputs the difference signal. Differential circuit 447
Receives the output signals of the differential circuits 445 and 446 and outputs the difference signal. This is the spherical aberration error (SA
E) It becomes a signal. Adder 448 receives the output signals of differential circuit 445 and differential circuit 446, and outputs the sum signal. This is a focus error (FE) signal.

The adder 449 detects the detection areas 521, 52
5, 523 and 527, and outputs the sum signal. The adder 450 includes detection areas 522, 52
6, 524, and 528, and outputs the sum signal. The phase difference TE generation circuit 451 includes the adder 4
Receiving the output signal of the adder 49 and the output signal of the adder 450, the phase is compared, and a phase difference TE signal is generated. The adder 452
It receives the output signals of adders 449 and 450 and outputs the sum signal. This becomes an RF signal.

An RF signal generating circuit 431 is composed of the three adders 449, 450 and 452. Adders 441-
The SAE signal generation circuit 432 includes the 444 and the differential circuits 445 to 447. Adders 441 to 444;
Differential circuits 445, 446 and adders 448, 449, 4
50 and the phase difference TE generation circuit 451, the FE signal T
The E signal generation circuit 433 is configured.

A beam provided with astigmatism in the 45-degree direction has an elliptical shape like a beam 381, for example. However, spherical aberration occurs, and the inner circumference near the optical axis of the beam and the outer circumference far from the optical axis are generated. In the case where defocus occurs, the beam on the inner circumference has an elliptical shape in the opposite direction to the beam 381, like the beam 382 in FIG. For this reason, the spherical aberration can be detected by the double left, right, upper, and lower light detection areas.

In the case of the present embodiment, the number of amplifiers required for reproducing the RF signal increases because the detection area increases, but the light loss is minimized because the light is not divided by the hologram element or the like. Thus, a high SN ratio can be maintained.

Further, a branching means for branching light is not required, and an optical head device can be manufactured at low cost.

[0116]

As described above, according to the present invention, an advantageous effect that a signal can be recorded and reproduced stably on an information storage medium having a high recording density can be obtained.

Further, an advantageous effect is obtained that an optical information processing apparatus capable of reproducing information from an information storage medium having a high recording density with a low error rate can be realized.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an optical system and a circuit block of an optical head device according to a first embodiment of the present invention.

FIG. 2 is a front view of hologram element 108 according to Embodiment 1 of the present invention.

FIG. 3 is a diagram showing an arrangement of beams, a configuration of a photodetector 111, and a configuration of peripheral circuits thereof according to the first embodiment of the present invention.

FIG. 4 is a configuration diagram of a current-voltage conversion circuit according to the first embodiment of the present invention.

FIG. 5 is a diagram showing a change in an SAE signal due to defocus according to the first embodiment of the present invention;

FIG. 6 is a front view of another hologram element 301 according to the first embodiment of the present invention.

FIG. 7 illustrates a configuration of a photodetector 111 when another hologram element 301 according to Embodiment 1 of the present invention is used.
Diagram showing the arrangement of some beams

FIG. 8 is a diagram showing a signal obtained when the focus is lost according to the first embodiment of the present invention;

FIG. 9 is a configuration diagram showing light reflected by the other information layer and a photodetector according to the first embodiment of the present invention.

FIG. 10 is a configuration diagram of another optical system and a circuit block according to the first embodiment of the present invention.

FIG. 11 is a front view of yet another hologram element 113 according to the first embodiment of the present invention.

FIG. 12 is a configuration diagram of an optical disk drive as an information recording / reproducing device using the optical head device 604 according to Embodiment 1 of the present invention.

FIG. 13 is a configuration diagram of an optical system and circuit blocks of an optical head device according to a second embodiment of the present invention.

FIG. 14 is a front view of the hologram element 114 according to the second embodiment of the present invention.

FIG. 15 is a diagram showing an arrangement of beams, a configuration of a photodetector 115, and a configuration of peripheral circuits thereof according to the second embodiment of the present invention.

FIG. 16 is a configuration diagram of an optical system and circuit blocks of an optical head device according to Embodiment 3 of the present invention.

FIG. 17 is a front view of hologram element 116 according to Embodiment 3 of the present invention.

FIG. 18 is a diagram showing an arrangement of beams, a configuration of a photodetector 117, and a configuration of a peripheral circuit thereof in Embodiment 3 of the present invention.

FIG. 19 is a configuration diagram of an optical system and a circuit block of an optical head device according to Embodiment 4 of the present invention.

FIG. 20 is a front view of a hologram element 304 according to Embodiment 4 of the present invention.

FIG. 21 is a diagram showing an arrangement of beams and a configuration of a photodetector 305 according to Embodiment 4 of the present invention.

FIG. 22 is a configuration diagram of an optical system and circuit blocks of an optical head device according to Embodiment 5 of the present invention.

FIG. 23 is a front view of the hologram element 308 according to the fifth embodiment of the present invention.

FIG. 24 is a diagram showing an arrangement of beams and a configuration of a photodetector 309 according to the fifth embodiment of the present invention.

FIG. 25 is a photodetector 3 according to a fifth embodiment of the present invention.
09 peripheral circuit configuration diagram

FIG. 26 is a configuration diagram of an optical system and circuit blocks of an optical head device according to Embodiment 6 of the present invention.

FIG. 27 is a diagram showing an arrangement of beams, a configuration of a photodetector 311 and a configuration of peripheral circuits thereof in Embodiment 6 of the present invention.

FIG. 28 is a configuration diagram of an optical system of a conventional optical head device.

FIG. 29 is a diagram showing a configuration and a beam arrangement of the photodetector 901 in FIG. 28;

[Explanation of symbols]

Reference Signs List 101 semiconductor laser 102 collimating lens 103 beam splitter 104 lens set 105 objective lens 106 actuator 107 optical disk 108, 113, 114, 116, 301, 303, 3
04,308 Hologram element 109 Detection lens 110 Cylindrical lens 112 Diffraction grating 111,115,117,305,309 Photodetectors 121-124,125-128,129,131-1
32,351-357,361-364,371-37
5,381-382,951 beams 151-155,156-157,171-174,5
01 to 509, 511 to 517, 911 to 914 Detection area 201 RF signal / FE signal / TE signal generation circuit 202, 407, 432 SAE signal generation circuit 203, 204, 206, 207 Control / drive circuit 205, 209, 408 FE Signal generation circuit 212 Rotation adjustment mechanism 251 ROT signal generation circuit 401, 431 RF signal generation circuit 402, 433 FE signal / TE signal generation circuit 403, 404 Arithmetic circuit 405 Differential circuit 406 TE signal generation circuit 601 Motor 602 Clamper 603 Traverse 604 Optical head device 605 Control circuit 1200 to 1213 Area 1301 to 1303 Division line

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshiaki Kanma 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. 72) Inventor Katsuhiko Yasuda 1006 Kadoma Kadoma, Kadoma City, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. CA05 CA23 CC17 CD02 CD04 CD06 CF10 DA33 DA43 DB07 DB15 DB16 5D119 BA01 BB13 EA03 EA10 EC01 JA09 JA24 KA08 KA22 LB06 LB13

Claims (17)

[Claims] A light source that emits light; a light-collecting optical system that includes light-collecting means that collects light emitted from the light source onto an information storage medium; and a return light reflected by the information storage medium. Branching means for splitting the light into a first light having a large light amount and a second light having a light amount smaller than the first light; and receiving the first light and recording the first light on the information storage medium. First light detection means for outputting a signal for reproducing information, and a second light receiving means for receiving the second light and outputting a signal for detecting an aberration of light condensed on the information storage medium An optical head device comprising: two light detecting means. 2. The optical head device according to claim 1, wherein the branching unit divides the second light into light in a first area near the optical axis and light in a second area far from the optical axis. A spherical aberration detecting means for detecting a spherical aberration of the light focused on the information storage medium by using at least one of a defocus amount of light in the area and a defocus amount of light in the second area. The optical head device according to claim 1, wherein: 3. The spherical aberration detector according to claim 2, wherein a difference between a defocus amount of light in the first region and a defocus amount of light in the second region is defined as a spherical aberration amount. Item 3. The optical head device according to item 2. 4. A cross section of light used in the condensing optical system is a substantially circular shape having a first radius, and has a second radius concentric with the substantially circular shape and smaller than the first radius. A circular region is defined as the first region, and a region outside the first region and inside a substantially circle having the first radius is defined as the second region.
3. The optical head device according to claim 2, wherein the region is a region defined by the following. 5. The amount of defocus of light in the first area and the amount of change of defocus of light in the second area when the relative distance between the information storage medium and the light condensing means changes. The optical head device according to claim 2, wherein: 6. The second light detection means includes a first light detection area for detecting light in the first area, and a second light detection area for detecting light in the second area. The first light detection area is arranged at a position closer to an optical axis of the first light branched by the branching unit than the second light detection area. The optical head device as described in the above. 7. The second light detecting means has a first light detecting area for detecting light in the first area, and a second light detecting area for detecting light in the second area. 3. The optical head device according to claim 2, wherein the first light detection area and the second light detection area share a part thereof. 8. The light-collecting optical system includes a spherical-aberration correcting unit that changes a spherical aberration of light condensed on the information storage medium, and the spherical-aberration correcting unit receives a signal from the spherical-aberration detecting unit. 3. The optical head device according to claim 2, wherein the optical head device operates upon receiving a signal. 9. The information storage medium has a track of a specific pitch, and the branching unit sets an area where a +1 order light and a 0 order light diffracted by the track overlap with an inner area + 1A
An outer region + 1B surrounding the region + 1A, an inner region -1A where a -1st order light and a 0th order light diffracted by the track overlap, and an outer region -1 surrounding the region -1A.
B, and a signal proportional to the light amount of the area + 1A and the area -1B
When a sum signal of a signal proportional to the light amount of the area + 1B is RT + and a sum signal of a signal proportional to the light amount of the area + 1B and the signal proportional to the light quantity of the area -1A is RT-, the signal RT + and the signal 2. The optical head according to claim 1, further comprising a tilt detecting unit configured to detect a tilt amount of the focusing optical system in a track direction on the information storage medium based on a difference signal from the signal RT-. apparatus. 10. A light source that emits light, a condensing optical system including a condensing unit that condenses the light emitted from the light source onto an information storage medium, and a return light reflected by the information storage medium. A branching unit that branches the light into a first region near the optical axis and a light in a second region far from the optical axis, and one light detecting unit that receives the branched light. When detecting the amount of spherical aberration of light condensed on the information storage medium using the difference between the defocus amount of light in the first area and the defocus amount of light in the second area, When the relative distance between the medium and the light condensing means changes, the first
An optical head device, wherein the amount of defocus of light in the region (b) is equal to the amount of defocus of light in the second region. 11. A cross section of light used in the condensing optical system is substantially circular, and the radius of the substantially circular is a first radius Rb, which is concentric with the substantially circular and is larger than the first radius Rb. A circular area having a small second radius R1 is defined as the first area, and the first area is outside the first area and the first radius Rb.
Is defined as the second area, and when the relative distance between the information storage medium and the condensing means changes, the defocus amount of light in the first area and the second area 11. The optical head device according to claim 10, wherein the ratio between the first radius Rb and the second radius R1 is determined so that the amount of change in the defocus amount of the light becomes equal. 12. A light source for emitting light, a sub-beam generating unit for generating a sub-beam from the light emitted from the light source, and a condensing unit for condensing the sub-beam and a main beam other than the sub-beam on an information storage medium. A light collecting optical system including: a first light having a large light amount and a second light having a small light amount as compared with the first light. Branching means for splitting the second light into light in a first area near the optical axis and light in a second area far from the optical axis; and receiving the first light, the information storage medium First light detection means for outputting a signal for reproducing information recorded on the information storage medium, and a signal for receiving the second light and detecting an aberration of the light collected on the information storage medium A second light detecting means for outputting a signal; And a third light detecting means for detecting the sub-beam emitted on the return path, wherein the second light detecting means and the third light detecting means are substantially orthogonal to the first light detecting means. An optical head device arranged in a direction. 13. A light source that emits light, a condensing optical system including a condensing unit that condenses the light emitted from the light source onto an information storage medium, and a return light reflected by the information storage medium. Branching means for splitting the light into a first light having a large light amount and a second light having a light amount smaller than the first light; and receiving the first light and recording the first light on the information storage medium. First light detection means for outputting a signal for reproducing information, and a second light receiving means for receiving the second light and outputting a signal for detecting an aberration of light condensed on the information storage medium A distance between the information storage medium and the light condensing means based on a sum signal of a signal from the first light detecting means and a signal from the second light detecting means; An optical head device comprising: means for determining that the distance is within the range. 14. A light source that emits light, a light-collecting optical system including light-collecting means that collects light emitted from the light source onto an information storage medium, and return light reflected by the information storage medium. Branching means for splitting the light into a first light having a large light amount and a second light having a light amount smaller than the first light; and receiving the first light and recording the first light on the information storage medium. First light detection means for outputting a signal for reproducing information, and a second light receiving means for receiving the second light and outputting a signal for detecting an aberration of light condensed on the information storage medium 2 light detecting means, the light amount of the first light is ηm, and the light amount of the second light is η
s, the numerical aperture of the light-collecting optical system is NA, the lateral magnification of the return path from the information storage medium of the light-collecting optical system to the first and second light detecting means is α, Where the optical spacing between the two reflecting surfaces of the information storage medium is d and the area of the detection region of the second light detecting means is S1, S1 ≦ 4 · π · (d · NA · α) ² · ηs / ηm 15. A light source for emitting light, a condensing optical system including a condensing means for condensing light emitted from the light source onto an information storage medium, and return light reflected on the information storage medium. Branching means into a first light having a large light amount and a second light having a small light amount as compared with the first light; and a branching means for receiving the first light and recording the first light on the information storage medium. First light detection means for outputting a signal for reproducing information, and a second light receiving means for receiving the second light and outputting a signal for detecting an aberration of light condensed on the information storage medium An optical head device having two light detecting units, a moving unit that relatively moves the optical head device and the information storage medium, and a control unit that controls the optical head device and the moving unit. An optical information recording / reproducing apparatus characterized by the above-mentioned. 16. A light source for emitting light, a condensing optical system including condensing means for condensing light emitted from the light source onto an information storage medium, and return light reflected by the information storage medium. Branching means for branching the light into a first light having a large light amount and a second light having a light amount smaller than the first light; a first light detecting means for receiving the first light; A second light detecting means for receiving the second light, the second light detecting means reproducing information recorded on an information storage medium using a signal from the first light detecting means; 2. An aberration detecting method, comprising detecting an aberration of light converged on the information storage medium using light from the second light detecting means. 17. A light source for emitting light, a condensing optical system including a condensing means for condensing light emitted from the light source onto an information storage medium, and a return light reflected by the information storage medium. Branching means for splitting light into a first area near the optical axis and light in a second area far from the optical axis; a rotating mechanism for rotating the splitting means with respect to the optical axis; An adjustment method for an optical head device, comprising: a first light detection area for detecting light, and light detection means having a second light detection area for detecting light in the second area, wherein the first Are divided by a dividing line substantially parallel to a straight line passing through the center of the optical axis of each light, and the first light detecting region is divided by the dividing line. 1A and a region 1B, and the second light detection region is divided into the division line by the division line. The area 1A is divided into an area 2A on the same side as the area 1A and an area 2B on the same side as the area 1B. The sum signal of the detection signal from the area 1A and the detection signal from the area 2B is S1, When the sum signal of the detection signal by the first signal 1B and the detection signal by the area 2A is S2, the branching means is used by using the rotating mechanism so that the difference signal between the sum signal S1 and the sum signal S2 becomes zero. And adjusting the optical head device.