JP2008016076A - Information processing device, photodetecting device, and optical pickup device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve such a problem that when a semiconductor laser in which a spread angle and an optical axis are varied by an output is used, the linearity of a front monitor light quantity and an objective lens going-out output is distorted, and an error is caused in the output control of the laser. <P>SOLUTION: Front monitor output S1, S2 from a photodetecting device 14 are corrected by a function of a first order or more in a laser control circuit 6. Also, each of the photodetecting device 14 and the laser control circuit 6 has such a constitution that a differential output for an optical axis varying monitor is provided at the front monitor. Thereby, a highly accurate light source light output monitor can be achieved at a low cost without adding any components. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an information processing device that optically records and reproduces information, an optical pickup device, and a configuration of a light detection device used for them.

  In recent years, information processing apparatuses that optically record and reproduce information, such as compact discs (hereinafter abbreviated as “CD”), Mini-Disk (hereinafter abbreviated as “MD”), Digital Versatile Disc (hereinafter abbreviated as “MD”). Hereinafter, a wide range of apparatuses for recording and reproducing various information (data) such as video, images, and audio on recording media such as “DVD”) and Blu-ray Disc (hereinafter abbreviated as “BD”). It is popular. In these apparatuses, a semiconductor laser is generally used as a light source for recording / reproducing information, and light obtained by emitting the semiconductor laser is condensed on a recording medium by a lens, and the optical output of the laser is increased on the recording medium. By increasing the light intensity of the light condensing spot, the physical properties of the recording medium are changed to record information such as marks, pits and magnetic information on the recording medium. During reproduction, information is reproduced by irradiating a light output lower than that and detecting a difference in physical properties (reflectance and magnetism) of the recording medium. In such an apparatus, the light source needs to emit light from low output to high output, and the optimum light intensity of the focused spot on the recording medium for stably recording information is determined by the scanning speed of the recording medium, Since the recording medium differs depending on the type and the solid, it is necessary to control the light output of the light source so that the optimum recording condition is always obtained during recording.

  In recent years, there has been a growing need for high-speed recording of information, and it is necessary to irradiate a recording medium with a high light intensity necessary for high-speed recording in order to meet the needs. This is because a method of increasing the scanning speed of the recording medium is generally used to perform high-speed recording on the same type of recording medium. However, when the scanning speed is increased, the recording medium is supplied with irradiated light. This is because the energy per unit area is reduced, and in order to ensure the light intensity necessary for recording, it is necessary to cause the light source to emit light with a higher light output.

  On the other hand, high-density recording of information (for example, CD → DVD → BD) is also progressing, and the physical size of marks to be recorded on a recording medium is decreasing. In order to stably form (record) a small mark on a recording medium, it is necessary to control the irradiation light intensity with high accuracy along with the time for irradiating the recording medium with light.

  For this reason, in general, the light output is controlled by receiving a part of light emitted from the light source with a photodetector and monitoring the light output of the light source (see, for example, Patent Document 1). . An outline of this prior art will be described with reference to FIGS.

  In FIG. 15, light 222 emitted from a semiconductor laser 221 as a light source is converted into parallel light by a collimator lens 223, and part of the parallel light passes through a reflection mirror 224 and enters a light output monitoring photodetector 225. To do. The output of the photodetector 225 is input to the laser control circuit 226, and the output of the semiconductor laser 221 is controlled to a required value. On the other hand, the light reflected by the reflection mirror 224 passes through the condenser lens 227 and is condensed on the recording medium 228. The light reflected from the recording medium 228 travels backward along the original path, is diffracted by the detection diffraction element 229, passes through the collimator lens 223, and detects signal detectors 2210 and 2211 in the vicinity of the semiconductor laser 221. Is incident on. Various signals such as focus, tracking, and RF are detected by the light incident on the photodetectors 2210 and 2211. The configurations of the photodetectors 2210 and 2211 and the detection methods of various signals are not essential components of the present invention, and various configurations are already known, and thus description thereof is omitted.

  FIG. 16 shows a far-field image of light emitted from the semiconductor laser 221 at this time. The centers of the aperture region 232 (region A) of the condensing lens 227 projected onto the far-field image 231 in FIG. 16 and the light-receiving region 233 (region B) of the light output monitoring photodetector 225 are the centers of the far-field image 231. It almost coincides with the center. Since the cross section of the intensity distribution of the far-field image 231 has a substantially normal distribution as shown in FIG. 17, the center of the aperture of the condenser lens 227 and the center of the light-receiving area of the photodetector 225 for light output monitoring are the far-field image. Since the use efficiency of the light from the light source is the highest when it is arranged so as to coincide with the center of the light, it is generally arranged in this way.

  Incidentally, in recent years, an actual refractive index guided laser that reduces the operating current of a semiconductor laser has been put to practical use in order to increase the output of the semiconductor laser and improve the high-temperature operating performance. In addition, the light emission angle varies in the horizontal direction depending on the light output. Here, the horizontal direction is defined as a direction along the active layer when the semiconductor laser is viewed from the light emitting surface side. Therefore, when monitoring the light output of the light source using an actual refractive index guided laser with such characteristics, the amount of light that passes through the condenser lens and is applied to the recording medium (hereinafter abbreviated as “Po”). ) And the amount of light incident on the light output monitoring photodetector (hereinafter abbreviated as “Pm”) is changed by the light output, and the linearity of Pm / Po can be secured. Therefore, it becomes difficult to perform accurate light output control.

  When a specific example is shown in FIG. 18, Pm / Po characteristics such as 252 and 253 are obtained with respect to the state 251 in which the linearity of Pm / Po is ensured. This is because the size and shape of the aperture region (referred to as region A) of the condenser lens and the light receiving region (referred to as region B) of the light output monitor photodetector are different in a general apparatus. This is because the efficiency (assumed to be ηA and ηB) combined by each of the regions A and B changes at different rates when the radiation angle of the semiconductor laser changes depending on the output. That is, assuming that the coupling efficiency when the optical output of the semiconductor laser is P1 is ηA1 and ηB1, respectively, and the coupling efficiency when the optical output is P2 (P1> P2) is ηA2 and ηB2, respectively, ηB1 / ηA1 ≠ ηB2 / ηA2 Therefore, the linearity of Pm / Po (= ηB / ηA) is broken.

The above-described semiconductor laser also has a feature that the peak position of the light intensity (hereinafter abbreviated as the optical axis) in the far-field image of the emitted light varies depending on the light output. Also in this case, due to the size and shape difference between the opening area A and the light receiving area B, ηB1 / ηA1 ≠ ηB2 / ηA2, and the problem that the linearity of Pm / Po (= ηB / ηA) is lost occurs.
Japanese Patent No. 2907759

  The problem to be solved is that, when the light emission angle and the optical axis of the light source are changed by the light output, the light amount Po that passes through the condenser lens and enters the recording medium, and the light detector for the light output monitor. Since the ratio of the incident light quantity Pm changes depending on the light output, the linearity of Pm / Po is lost and it becomes impossible to monitor the light output accurately, and an error occurs in the output control of the light source performed by monitoring Pm. The recording / reproducing performance of the apparatus is impaired.

  The present invention is an information processing apparatus that irradiates a recording medium with light from a light source and records and reproduces information on the recording medium, and a condenser lens that condenses the light from the light source on the recording medium; A light detection device that receives a part of the light from the light source; and a control circuit that controls an output of the light source using a signal from the light detection device; and a far-field image of the light from the light source. The aperture area A of the condenser lens projected onto the light intensity distribution and the light receiving area B of the light detection device projected onto the light intensity distribution of the far-field image of the light from the light source are different in size. The first main feature is that the output of the light source is controlled using a signal S ′ obtained by adding a first-order or higher-order function related to the signal S to the signal S with respect to the signal S obtained from the light detection device. .

  In addition, the photodetector has a plurality of axisymmetric photodetectors and outputs a sum signal and a difference signal of signals obtained from the plurality of photodetectors as a second main feature. .

  The photodetector includes a plurality of axisymmetric photodetectors and a single photodetector, a difference signal between signals obtained from the plurality of photodetectors, and the single photodetector. The third main feature is to output a signal obtained from the above.

  In the present invention, even when the light emission angle and the optical axis of the light source change depending on the light output, the light amount Po that passes through the condenser lens and enters the recording medium, and the light amount that enters the photodetector for light output monitoring. By suppressing the change due to the light output of the ratio to Pm and ensuring the linearity of Pm / Po, it is possible to realize an apparatus having accurate light output monitoring performance.

  Even when the light emission angle in the horizontal direction of the light source varies depending on the light output, a configuration that achieves high linearity and high-precision light output monitoring performance has been realized.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same reference numerals denote the same or equivalent components.

(Embodiment 1)
FIG. 1 is a configuration diagram of an information processing device including the photodetector and the optical pickup device according to the first embodiment of the present invention.

  In FIG. 1, light 2 emitted from a semiconductor laser 1 as a light source is reflected by a bending mirror 13, then converted into parallel light by a collimating lens 3, reflected by a reflecting mirror 4, transmitted through a diffraction element 9, and condensed. The light is condensed on the recording medium 8 by the lens 7. On the other hand, the light transmitted through the bending mirror 13 enters the photodetector 5 for monitoring the optical output, but the size of the light receiving portion of the photodetector 5 is smaller than the light beam 12 incident on the condenser lens 7, and the photodetector The center of the light receiving part 5 substantially coincides with the center of the light beam 12. The light reflected from the recording medium 8 follows the original path in reverse, but is diffracted by the diffraction element 9 and is incident on the signal detection photodetectors 10 and 11 in the vicinity of the semiconductor laser 1. Various signals such as focus, tracking, and RF are detected by the light incident on the photodetectors 10 and 11. The configuration of the photodetectors 10 and 11 and the detection method of various signals are not essential components of the present invention, and various configurations are already known, and thus description thereof is omitted.

  FIG. 2 shows the relationship between the aperture region 112 (region A) of the condenser lens 7 and the light receiving region 113 (region B) of the photodetector 5 projected onto the far-field image of the emitted light from the semiconductor laser 1. The horizontal radiation angle of the semiconductor laser 1 varies depending on the output. The horizontal radiation angle (full width at half maximum) θh1 at the output P1 is 7 °, and the horizontal radiation angle (full width at half maximum) θh2 at P2 is 9. °, vertical radiation angle (full width at half maximum) θv is 14 °, constant regardless of output, region A is circular, and the radiation angle (full angle) viewed from the light source is 12.4 ° in both horizontal and vertical directions. FIGS. 3 and 4 are graphs showing changes in ηA and ηB with respect to changes in θh, respectively, where B is also circular, and the radiation angle (full angle) viewed from the light source is 2 ° in both the horizontal and vertical directions. When θh increases from 7 ° to 9 °, ηA decreases by 10% and ηB decreases by 22%. This is because the region B is smaller than the region A, and thus the degree of influence on the change in coupling efficiency due to the change in θh is large. Since the output control of the light source is generally performed by monitoring the output S from the photodetector 5, it is desirable that the ratio between the output S and the light output Pol emitted from the condenser lens 7 is constant. That is, it is desirable that ηB / ηA is constant. In this example, as shown in FIG. 5, ηB / ηA decreases by 13% when θh increases from 7 ° to 9 °.

  Consider the effect of this phenomenon on the output control of the light source. When the value when θh = 7 ° is used as a coefficient representing the relationship between the output S and Pol, when the output S is plotted on the horizontal axis and Pol is plotted on the vertical axis, the relationship is graphed as shown in FIG. Become. In general, the output control of the light source is performed assuming the characteristic of the broken line in FIG. 6, whereas the actual relationship between the output S and Pol is a characteristic of the solid line, and the control error is about 15% at the point of θh = 9 °. Will occur.

  In this example, θh is expanded by 2 ° from 7 ° to 9 ° due to the light output. If the difference of θh is defined as Δθh, generally Δθh is generally proportional to the light output in many cases. . FIG. 7 shows the relationship between the optical output of a semiconductor laser and Δθh. In the case of this semiconductor laser, Δθh changes by about 2 ° at an optical output of 1 to 300 mW, but changes almost linearly. Therefore, the characteristics shown in FIG. 6 are almost the same when a semiconductor laser of the same kind is used. Here, when the difference between the characteristic of the solid line in FIG. 6 and the characteristic of the broken line is expressed as a function f (S) of the output S, it can be expressed by a quadratic or linear function as shown in FIG. Here, S is normalized by the value at the maximum output. If the control target value of Pol is Pol ′, the control error can be suppressed by controlling as Pol ′ = S−f (S).

  In this embodiment mode, the configuration example of the area A (area)> the area B (SB) has been described. However, the present invention can be applied even when the area A is smaller than the area B due to the configuration of the apparatus. It is clear that it can be applied.

  In this embodiment, the example in which the emission angle of the semiconductor laser as the light source changes in the horizontal direction according to the light output has been described. .

(Embodiment 2)
FIG. 9 is a configuration diagram of an information processing apparatus including the light detection device and the optical pickup device according to the second embodiment of the present invention. Since the operation of light from the light source is the same as that in Embodiment 1, the description thereof is omitted.

  In the present embodiment, the light receiving area of the light detection device 14 for monitoring light output is divided into two light detectors 15 and 16 that are symmetrical in the horizontal direction, as shown in FIG. Outputs from the photodetectors 15 and 16 are generated by a summing circuit 17 as a sum signal S1 and a subtraction circuit 18 as a difference signal S2 and output from the light detection device 14 and input to the laser control circuit 6.

  The relationship and shape of the aperture region 112 (region A) of the condenser lens 7 and the light receiving region 113 (region B) of the light detection device 14 projected onto the far-field image of the light emitted from the semiconductor laser 1 and the light source The radiation angle of each region is the same as that of the first embodiment and is as shown in FIG. Here, the horizontal radiation angle of the semiconductor laser 1 varies depending on the output, the horizontal radiation angle (full width at half maximum) θh1 at the output P1 is 7 °, and the horizontal radiation angle (full width at half maximum) at P2. θh2 is 9 °, and the vertical radiation angle (full width at half maximum) θv is constant regardless of the output, and θv = 14 °. FIG. 11 shows the characteristics of ηB and ηA with respect to changes in θh when the horizontal optical axis φh of the semiconductor laser 1 is 0 ° and 1 °. Note that ηB and ηA are normalized with values of θh = 7 ° and φh = 0 °. A curve 22 in the graph is obtained when φh = 0 °, which is the same as the characteristic described in the first embodiment. By the invention described in the first embodiment, ηB / ηA = It can be corrected to be 1. The curve 23 is obtained when φh = 1 °. However, at the point of θh = 9 °, ηB / ηA = 0.98, which is 13 compared to the value (0.87) of the curve 22 at θh = 9 °. % Deviation occurs. In this example, the signal corresponding to ηB is obtained by the sum signal S1. On the other hand, a signal corresponding to the change in the optical axis can be obtained from the difference signal S2. Since the rate at which ηB / ηA changes is the same regardless of whether the optical axis changes in the horizontal direction, the difference signal S2 does not require polarity. Therefore, in FIG. 10, the difference signal S2 is converted into an absolute value by the absolute value conversion circuit 19 in the laser control circuit 6, and the signal S2 ′ subjected to gain conversion by the gain variable amplifier (VGA) 20 is converted from the sum signal S1 to the differential amplifier 21. Thus, the curve 23 in FIG. 11 can be improved to the curve 23 ′. Thereby, the deviation with respect to the curve 22 can be suppressed to ± 9% or less. At this time, the gain of the adding circuit 17, the subtracting circuit 18 and the absolute value converting circuit 19 is 1, and the gain of the variable gain amplifier 20 is 1.3.

  In recent years, semiconductor lasers that are put into practical use include those in which the optical axis changes as well as the variation in θh due to the light output. As described above, many changes in θh due to light output are almost proportional to light output. However, the change in the optical axis has a low correlation with the light output, and the direction and amount of change are not uniform. Although the correction as in the first aspect of the invention is impossible, if the invention of the present embodiment is used, the amount corresponding to the change in the optical axis can be monitored in real time. Errors can be suppressed.

  In this embodiment mode, the configuration example of the area A (area)> the area B (SB) has been described. However, the present invention can be applied even when the area A is smaller than the area B due to the configuration of the apparatus. It is clear that it can be applied.

  In this embodiment, the example in which the emission angle of the semiconductor laser as the light source changes in the horizontal direction according to the light output has been described. .

(Embodiment 3)
FIG. 12 is a configuration diagram of an information processing apparatus including the photodetector and the optical pickup device according to the third embodiment of the present invention. Since the operation of light from the light source is the same as that in Embodiment 1, the description thereof is omitted.

  In the present embodiment, as shown in FIG. 13, a single photodetector 25 and photodetectors 26 and 27 symmetrical in the horizontal direction are arranged in the light receiving region of the light output monitoring photodetector 24. The output from the light detector 25 is the signal S1, and the outputs from the light detectors 26 and 27 are the difference signal S2 generated by the subtraction circuit 18 from the light detection device 24 and input to the laser control circuit 6.

  The relationship and shape of the aperture region 112 (region A) of the condenser lens 7 and the light receiving region 113 (region B) of the light detection device 24 projected onto the far-field image of the light emitted from the semiconductor laser 1 and the light source The radiation angle of each region is the same as that of the first embodiment and is as shown in FIG. Here, the horizontal radiation angle of the semiconductor laser 1 varies depending on the output, the horizontal radiation angle (full width at half maximum) θh1 at the output P1 is 7 °, and the horizontal radiation angle (full width at half maximum) at P2. θh2 is 9 °, and the vertical radiation angle (full width at half maximum) θv is constant regardless of the output, and θv = 14 °. FIG. 14 shows the characteristics of ηB and ηA with respect to changes in θh when the horizontal optical axis φh of the semiconductor laser 1 is 0 ° and 1 °. Note that ηB and ηA are normalized with values of θh = 7 ° and φh = 0 °. A curve 28 in the graph is obtained when φh = 0 °, which is almost the same as the characteristic described in the first embodiment, and according to the invention described in the first embodiment, ηB / ηA regardless of θh variation. Can be corrected to be = 1. The curve 29 is obtained when φh = 1 °. However, at the point of θh = 9 °, ηB / ηA = 0.98, which is 13 compared to the value (0.87) of the curve 28 at θh = 9 °. % Deviation occurs. In this example, the signal corresponding to ηB is obtained by the signal S1. On the other hand, a signal corresponding to the change in the optical axis can be obtained from the difference signal S2. The difference signal S2 in FIG. 13 is converted into an absolute value by the absolute value conversion circuit 19 in the laser control circuit 6, and the signal S2 ′ subjected to gain conversion by the gain variable amplifier (VGA) 20 is changed by the differential amplifier 21 from the sum signal S1. The curve 29 in FIG. 13 can be improved to the curve 30 by performing dynamic calculation. Thereby, the deviation with respect to the curve 28 can be suppressed to ± 9% or less. At this time, the gain of the adding circuit 17, the subtracting circuit 18 and the absolute value converting circuit 19 is 1, and the gain of the variable gain amplifier 20 is 4.

  In this embodiment mode, the configuration example of the area A (area)> the area B (SB) has been described. However, the present invention can be applied even when the area A is smaller than the area B due to the configuration of the apparatus. It is clear that it can be applied.

  In this embodiment, the example in which the emission angle of the semiconductor laser as the light source changes in the horizontal direction according to the light output has been described. .

  Further, in this example, the photodetectors 25, 26, and 27 are arranged in the region B. However, it is the same even if the photodetectors 26 and 27 are arranged symmetrically outside the region as the region B = the photodetector 25. Effects can be obtained. In this case, the gain of the variable gain amplifier 20 may be adjusted to an optimum value in each configuration.

  It is also possible to apply the difference signal S2 to other than the light output control of the light source. For example, since the tracking error signal and the wobble signal detection from the recording medium are easily affected by the fluctuation of the optical axis, the differential signal S2 may be used as a correction signal for detecting these signals.

  Needless to say, the pickup apparatus according to each embodiment can be used as a component of an information processing apparatus that performs recording and reproduction by irradiating a recording medium with light from a light source.

  The light detection device, the optical pickup device, and the information processing device according to the present invention can realize a device having high-precision light source light output monitoring performance at low cost without adding any components, and can be used as a light source. Since the required performance range can be widened, it has the effect of facilitating the procurement of the light source, which is the main component, and is useful as various devices and devices such as optical disk drives, players, recorders, etc. for optical recording and reproduction.

Schematic diagram illustrating the configuration of the information processing apparatus according to the first embodiment of the present invention. Conceptual diagram for explaining a far-field image in the information processing apparatus Characteristic diagram showing coupling efficiency ηA in the information processing apparatus Characteristic diagram showing coupling efficiency ηB in the information processing apparatus Characteristic diagram showing coupling efficiency ηB / ηA in the information processing apparatus Pol characteristic chart for output S in the information processing apparatus Characteristic diagram of Δθh with respect to optical output in the information processing apparatus Characteristic diagram of F (S) with respect to output S in the information processing apparatus Schematic diagram illustrating the configuration of the information processing apparatus according to the second embodiment of the present invention. Schematic diagram showing the configuration of the photodetector and laser control circuit in the information processing apparatus Characteristic diagram showing coupling efficiency ηB / ηA in the information processing apparatus Schematic diagram illustrating the configuration of the information processing apparatus according to the third embodiment of the present invention. Schematic diagram showing the configuration of the photodetector and laser control circuit in the information processing apparatus Characteristic diagram showing coupling efficiency ηB / ηA in the information processing apparatus Schematic diagram showing the configuration of a conventional information processing apparatus Conceptual diagram for explaining a far-field image in a conventional information processing apparatus Characteristic diagram showing the intensity distribution of a far-field image in a conventional information processing apparatus Characteristic diagram showing the relationship between Po and Pm in a conventional information processing apparatus

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor laser 2 Light emitted from semiconductor laser 3 Collimating lens 4 Reflecting mirror 5 Photo detector 6 Laser control circuit 7 Condensing lens 8 Recording medium 9 Diffraction element 12 Light flux on reflecting mirror 13 Bending mirror 14 Photodetector

Claims (12)

An information processing apparatus for irradiating a recording medium with light from a light source and recording / reproducing information on the recording medium, the condenser lens for condensing the light from the light source onto the recording medium, and from the light source A light detection device that receives a part of the light, and a control circuit that controls an output of the light source using a signal from the light detection device, on a light intensity distribution of a far-field image of the light from the light source The aperture area A of the condensing lens projected onto the light-receiving area B of the photodetection device projected onto the light intensity distribution of the far-field image of the light from the light source is different in size from the photodetection device An information processing apparatus that controls an output of the light source using a signal S ′ obtained by adding a first-order or higher function related to the signal S to the signal S with respect to the obtained signal S. The information processing apparatus according to claim 1, wherein an area SA of the opening region A and an area SB of the light receiving region B have a relationship of SA> SB. The light source is a semiconductor laser, and when the thickness direction of the active layer of the semiconductor laser is defined as the vertical direction, the center of the far-field image of the light from the semiconductor laser and the center of the opening region A are substantially coincident. The information processing apparatus according to claim 1, wherein the center of the opening region B substantially coincides with the center of the far-field image in at least one of a horizontal direction and a vertical direction. A light detection device for use in an information processing apparatus that irradiates light from a light source onto a recording medium and records / reproduces information on the recording medium, wherein the information processing apparatus collects light from the light source on the recording medium. A light collecting lens, and the light detection device is disposed at a position for receiving a part of the light from the light source, and is on a light intensity distribution of a far-field image of the light from the light source. The projected aperture area A of the condensing lens and the light receiving area B of the light detection device projected onto the light intensity distribution of the far-field image of the light from the light source have different sizes, and the light detection device has an axis An optical detection apparatus comprising a plurality of symmetrical photodetectors and outputting a sum signal and a difference signal of signals obtained from the plurality of photodetectors. A light detection device for use in an information processing apparatus that irradiates light from a light source onto a recording medium and records / reproduces information on the recording medium, wherein the information processing apparatus collects light from the light source on the recording medium. A light collecting lens, and the light detection device is disposed at a position for receiving a part of the light from the light source, and is on a light intensity distribution of a far-field image of the light from the light source. The projected aperture area A of the condensing lens and the light receiving area B of the light detection device projected onto the light intensity distribution of the far-field image of the light from the light source have different sizes, and the light detection device has an axis A plurality of symmetrical photodetectors and a single photodetector, which outputs a difference signal of signals obtained from the plurality of photodetectors and a signal obtained from the single photodetector; An optical detection device characterized by that. An optical pickup device that irradiates a recording medium with light from a light source and records and reproduces information on the recording medium, the optical pickup device including a condensing lens that condenses the light from the light source on the recording medium; A light detection device that receives a part of the light from the light source, the aperture region A of the condenser lens projected onto the light intensity distribution of the far-field image of the light from the light source, and the light source The light detection area B of the light detection device projected on the light intensity distribution of the far-field image of the light of the light has a size different from that of the light detection region B, and the light detection device has a plurality of axisymmetric light detectors, An optical pickup device that outputs a sum signal and a difference signal of signals obtained from a detector. An optical pickup device that irradiates a recording medium with light from a light source and records and reproduces information on the recording medium, the optical pickup device including a condensing lens that condenses the light from the light source on the recording medium; A light detection device that receives a part of the light from the light source, the aperture region A of the condenser lens projected onto the light intensity distribution of the far-field image of the light from the light source, and the light source The light detection area B of the light detection device projected onto the light intensity distribution of the far-field image of the light of the light has a size different from that of the light detection region B, and the light detection device includes a plurality of axisymmetric light detectors and a single light detector. And an optical pickup device that outputs a difference signal between signals obtained from the plurality of photodetectors and a signal obtained from the single photodetector. 8. The optical pickup device according to claim 6, wherein the area SA of the opening region A and the area SB of the light receiving region B have a relationship of SA> SB. The light source is a semiconductor laser, and when the thickness direction of the active layer of the semiconductor laser is defined as the vertical direction, the center of the far-field image of the light from the semiconductor laser and the center of the opening region A are substantially coincident. 9. The optical pickup device according to claim 6, wherein the center of the aperture region B substantially coincides with the center of the far-field image in at least one of a horizontal direction and a vertical direction. . An information processing apparatus that irradiates a recording medium with light from a light source and records and reproduces information on the recording medium, the information processing apparatus including a condenser lens that condenses the light from the light source on the recording medium; A light detection device that receives a part of the light from the light source, the aperture region A of the condenser lens projected onto the light intensity distribution of the far-field image of the light from the light source, and the light source The light detection area B of the light detection device projected on the light intensity distribution of the far-field image of the light of the light has a size different from that of the light detection region B, and the light detection device has a plurality of axisymmetric light detectors, An information processing apparatus that outputs a sum signal and a difference signal of signals obtained from a detector, and performs light output control of the light source using a signal obtained by performing arithmetic processing on the sum signal and the difference signal . An optical information processing apparatus for irradiating a recording medium with light from a light source and recording / reproducing information on the recording medium, wherein the information processing apparatus condenses light from the light source on the recording medium And a light detecting device that receives a part of the light from the light source, the aperture area A of the condenser lens projected onto the light intensity distribution of the far-field image of the light from the light source, and the light source The light detecting device projected on the light intensity distribution of the far-field image of the light from the light receiving region B of the light detecting device is different in size, and the light detecting device has a plurality of axisymmetric light detectors and a single light detecting device. A signal obtained by calculating the difference signal of the signals obtained from the plurality of photodetectors and the signal obtained from the single photodetector, and processing the sum signal and the difference signal An information processing apparatus that performs light output control of the light source using a light source. 12. The information processing apparatus according to claim 10, wherein a correction is applied to at least one of an information signal obtained from the recording medium and a control error signal using the difference signal.

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