JPH087298A - Optical information recording / reproducing device - Google Patents

Abstract

(57) [Abstract] [Purpose] Optical information recording that can prevent the occurrence of AT and AF offsets, does not cause positional deviation of recorded information, and does not deteriorate reproduced signals, and can maintain the quality of recorded information and reproduced signals at a constant level. Realize a playback device. A light splitting element 25 that splits a light beam limited by an aperture 24 into a plurality of light beams, and reflected light when the plurality of light beams are applied to a recording medium 1 is detected by an auto-tracking photodetector and an auto-focusing photodetector. In an optical information recording / reproducing apparatus including an optical head having a detection optical system for guiding to a plurality of divided photodetectors 31 including a light dividing element, the position of the light dividing element 25 is The position adjusting mechanism 101 adjusts and holds the difference signal between the output of the auto-tracking photodetector and the output of the autofocusing photodetector at an extreme value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording / reproducing apparatus for recording and / or reproducing information on an optical information recording medium.

[0002]

2. Description of the Related Art Conventionally, various types of information recording media for recording and reproducing information using light have been known, such as disk, card, tape and the like. Some of these optical information recording media are recordable and reproducible, and only reproducible. Recording of information on a recordable medium is performed by scanning an information track with a light beam that is modulated according to the record information and focused into a minute spot, and the information is recorded as an optically detectable information bit string. .

Information is reproduced from a recording medium by scanning an information bit string of an information track with an optical beam spot having a constant power such that recording is not performed on the medium and reflecting or transmitting light from the medium. Is detected.

The above-mentioned optical head used for recording and reproducing information on the recording medium is movable relative to the recording medium in the information track direction and in the direction transverse to the direction, and by this movement, the optical head is moved. Information track scanning of the beam spot is performed. An objective lens, for example, is used as a lens for narrowing the light beam spot in the optical head. The objective lens can be independently moved in its optical axis direction (focusing direction) and in a direction (tracking direction) orthogonal to both the optical axis direction and the information track direction of the recording medium. Held in. Such holding of the objective lens is generally performed through an elastic member, and the movement of the objective lens in the above two directions is generally driven by an actuator utilizing magnetic interaction.

Among the above-mentioned optical information recording media, a card-shaped optical information recording medium (hereinafter referred to as an optical card) is a small-sized, light-weight, convenient-to-carry, relatively large-capacity information recording medium, which will be large in the future. Demand is expected.

FIG. 7 is a schematic plan view of a write-once optical card, and FIG. 8 is a partially enlarged view thereof.

In FIG. 7, a large number of information tracks 2 are arranged on the information recording surface of the optical card 1 in parallel with the LF direction. The information recording surface of the optical card 1 is provided with a home position 3 which serves as a reference position for accessing the information track 2. The information track 2 is in the order of 2-1, 2-2, 2-3, ...
As shown in FIG. 8, tracking tracks 4 are provided adjacent to these information tracks 4-1 and 4-.
2, 4, 3, ... are sequentially provided. These tracking tracks 4 are used as guides for auto-tracking (hereinafter, referred to as AT) that controls the beam spot so that the beam spot does not deviate from a predetermined information track at the time of scanning the light beam spot during information recording / reproduction. .

This AT servo detects the deviation (AT error) of the light beam spot from the information track in the optical head, negatively feeds back the detection signal to the tracking actuator, and the objective lens is attached to the optical head main body. This is performed by moving in the tracking direction (D direction) and causing the light beam spot to follow a desired information track.

Further, during information recording / reproduction, when scanning an information track with a light beam spot, in order to make the light beam into a spot shape (focus) of an appropriate size on the optical card surface, Focusing (hereinafter referred to as AF) servo is performed. This AF servo detects a deviation (AF error) from the focused state of the light beam spot in the optical head, negatively feeds back the detection signal to the focusing actuator, and moves the objective lens to the optical head main body in the focusing direction. By moving the light beam spot to the optical card surface to focus the light beam spot on the optical card surface.

In FIG. 8, S₁, S₂, S₃Is
Shows the light beam spot, S₁And S ₃Use the light spot of
And use AT to do S₂AF using the light spot of
And the creation of information bits during recording and
Read out. In each information track, 6-
1, 6-2 and 7-1, 7-2 are preformatted respectively
The left side address part and the right side address part are shown.
The information track can be identified by reading the address section.
Be played. 5 (corresponding to 5-1 and 5-2 in the figure) is the data
This is a data section in which predetermined information is recorded.

Here, an optical information recording method will be described with reference to the schematic view of the optical head optical system shown in FIG.

In FIG. 9, reference numeral 21 denotes a semiconductor laser which is a light source, and in this example, emits light having a wavelength of 830 nm which is polarized in the direction perpendicular to the track. Further, 22 is a collimator lens, 23 is a beam shaping prism, 24 is an aperture, 25 is a diffraction grating for splitting a light beam, 25 'is a diffraction grating portion, and 26 is a polarization beam splitter. Furthermore,
27 is a quarter wavelength plate, 28 is an objective lens, 29 is a spherical lens, 30 is a cylindrical lens, and 31 is a photodetector.

As shown in FIG. 4, the photodetector 31 is composed of two light receiving elements 31a and 31c and four light receiving elements 31b.

The light beam emitted from the semiconductor laser 21 becomes an elliptical divergent light beam and enters the collimator lens 22. Then, a parallel light beam is formed by the lens,
Further, it is shaped into a circular beam by the beam shaping prism 23. The intensity of light emitted from the semiconductor laser 21 has a Gaussian distribution and propagates while maintaining a Gaussian distribution state.

After that, the light beam is restricted by the aperture 24 in order to obtain a predetermined recording / reproducing spot, and the diffraction grating 2
It is incident on 5. By the diffraction grating portion 25 'having a diameter smaller than the incident light beam diameter, it is divided into three effective light beams (0th order diffracted light and ± 1st order diffracted light). The three light beams have different diameters for their respective purposes. In this case, the 0th-order diffracted light is composed of diffracted light and non-diffracted light, and the 0th-order diffracted light beam diameter is dominated by the non-diffracted light beam. Naturally, the diameter of the 0th-order diffracted light flux is larger than the diameter of the ± 1st-order diffracted light flux of only the diffracted light. In a normal configuration, the diffraction grating generates 0th-order diffracted light and ± 1st-order diffracted light having the same light beam diameter to generate a 3-beam A
It is generally used for the T system, but in order to make the AT control more accurate, or to further improve the recording density and the recording speed, as described above, the 0th-order diffracted light and ± A method has been considered in which the light flux diameters of the first-order diffracted lights are made different. The three light beams split by the diffraction grating 25 enter the polarization beam splitter 25 as P-polarized light beams.

Next, the three light beams are converted into a quarter wave plate 2
It is converted into circularly polarized light when passing through 7, and is focused on the optical card 1 by the objective lens 28. The focused light is converted into three minute beam spots S ₁ (+ _{1st order} diffracted light), S ₂
(0th order diffracted light) and S ₃ (−1st order diffracted light). S ₂ is used for recording, reproduction and AF control, and S ₁ and S ₃ are used for AT control. The spot position on the optical card 1 is, as shown in FIG. 8, the light beam spots S ₁ and S ₃
Are located on the adjacent tracking tracks 4, and the light beam spot S ₂ is located on the information track 2 between the tracking tracks. Thus, the reflected light from the light beam spot formed on the optical card 1 passes through the objective lens 28 again to be a parallel light beam, which passes through the quarter-wave plate 27 and has a polarization direction 90 degrees from that at the time of incidence. ° Converted to a rotated light beam. Then, it enters the polarization beam splitter 26 as an S-polarized beam.

A spherical optical lens 29 and a cylindrical lens 30 are combined in the detection optical system, and the AF control by the astigmatism method is performed by this combination. The three light beams reflected from the optical card 1 are respectively collected by the detection optical system and enter the photodetector 31 shown in FIG. 4 to form three light spots. Light receiving elements 31a, 3
1c receives the reflected light from the light spots S ₁ and S ₃ described above,
AT control is performed using the difference between the outputs of these two light receiving elements. The light receiving element 31b of the 4 division receives the reflected light of the light spot S _2, and recorded information is carried out AF control using the output is reproduced.

By moving the entire optical head optical system as described above relative to the recording medium, it is possible to scan the information track with the light beam spot S ₂ .

[0019]

However, in the above-mentioned conventional example, since there is no means for making the center of the light beam limited by the aperture 24 coincide with the center of the diffraction grating portion 25 'of the diffraction grating 25, the diffraction grating 25 is not provided. There is a drawback that the light intensity distributions of the 0th-order diffracted light and the ± 1st-order diffracted lights emitted from are not axisymmetric with respect to the center of the light flux. That is, the intensity distribution of the light flux is no longer a Gaussian distribution.

In this case, as shown in the optical cross section of FIG.
The central axis 53 (marked by Δ in the figure) of the diffraction grating portion 25 ′ of the diffraction grating 25 is set to be deviated from the central axis 52 (marked by x in the figure) of the light beam 51 limited by the aperture 24. In such a state, the light intensity distributions of the three diffracted lights from the diffraction grating 25 become as shown in FIGS. 6A and 6B, respectively. FIG. 6A shows a light intensity distribution of ± first-order diffracted light beams,
FIG. 6B shows the light intensity distribution of the 0th-order diffracted light beam. As can be seen from the light intensity distribution, the light beams are asymmetric with respect to the central axis of each light beam.

When the symmetry of the light intensity distribution of the light flux is lost in this way, two major obstacles occur. One of them is the AT offset. As shown in FIG. 8, but is disposed with respect to the optical spot S _1, S ₃ respectively, AF and reproducing light spot S ₂ for AT to inner tracks (possible outside), S ₁ and S ₃ are Since they are ± first-order diffracted lights, their light intensity distributions are exactly the same as each other.
When the AT control (three-beam AT method) is performed so that the output of the photodetector 31a and the output of 31c are equal to each other, an offset is inevitably generated, which causes positional deviation of recorded information or deterioration of a reproduction signal. The problem arises that it will occur.

Another obstacle is AF offset. The AF control is controlled so that the difference between the sums of the outputs of the four-divided photodetector 31b shown in FIG. 4 in both plow directions becomes 0 (the astigmatism AF method), so that the light intensity distribution naturally changes. When it occurs, it affects each detector output of the photodetector 31b, and an offset occurs. When the offset occurs, there arises a problem that the quality of recorded information and reproduced signal cannot be kept constant.

[Object of the Invention] An object of the present invention is to match the center of a light beam limited by an aperture with the center of a diffraction grating as a light splitting element, so that the light intensity distributions of a plurality of light beams emitted from the diffraction grating are matched. Is made to be axially symmetric with respect to the center of the light flux, thereby eliminating the occurrence of AT and AF offsets, keeping the quality of the recorded information and the reproduced signal constant without causing the positional deviation of the recorded information and the deterioration of the reproduced signal. It is to realize an optical information recording / reproducing device capable of performing the above.

[0024]

[Means and Actions for Solving the Problems]

[Means and Action A] According to the present invention, a light source, an aperture for limiting a light beam emitted from the light source, a light splitting element for splitting a part of the light beam limited by the aperture into a plurality of light beams, and the light A position adjusting mechanism for the splitting element, an objective lens for converging the plurality of light fluxes into a minute spot on an optical information recording medium, and a reflected light from the optical information recording medium transmitted through the objective lens in a direction different from the outward path. An optical head composed of a light splitting means for splitting into a plurality of light splitting means, and a detection optical system for guiding the light flux split by the light splitting means to a plurality of split photodetectors for auto-focusing and auto-focusing. An optical information recording / reproducing apparatus which records and / or reproduces information by moving a light beam emitted from the optical head relative to the optical information recording medium. In the position where the difference signal between the output of the auto-tracking photodetector and the output of the auto-focusing photodetector has an extreme value, the light splitting element such as the diffraction grating is provided with the diffraction grating (light splitting element). ) Adjust the position using the position adjustment mechanism.

As a result, the center of the light beam limited by the aperture and the center of the diffraction grating as the light splitting element are made to coincide with each other, and the light intensity distributions of the plurality of light beams emitted from the diffraction grating are axially symmetrical with respect to the center of the light beam. Can be A
In the T and AF controls, it is possible to achieve an optical information recording / reproducing apparatus that can perform stable control without offset.

[Means and Action B] According to the present invention, the diffraction grating is positioned by the diffraction grating position adjusting mechanism at a position where the outputs of the plurality of divided photodetectors for autofocusing become equal. adjust.

As a result, the center of the light beam limited by the aperture and the center of the diffraction grating as the light splitting element are made to coincide with each other, and the light intensity distributions of the plurality of light beams emitted from the diffraction grating are axially symmetric with respect to the center of the light beam. Can be A
In the T and AF controls, it is possible to achieve an optical information recording / reproducing apparatus that can perform stable control without offset.

[Means and Action C] According to the present invention, a position adjusting mechanism for the light splitting element is provided for the light beam limited by the aperture, and the light splitting element is divided into a plurality of pieces. The position is adjusted so that the output value of one of the photodetectors takes an extreme value.

As a result, the center of the light beam limited by the aperture and the center of the diffraction grating as the light splitting element are made to coincide with each other, and the light intensity distributions of the plurality of light beams emitted from the diffraction grating are axially symmetric with respect to the center of the light beam. Can be A
In the T and AF controls, it is possible to achieve an optical information recording / reproducing apparatus that can perform stable control without offset.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the optical information recording / reproducing apparatus of the present invention will be described in detail below with reference to the drawings.

[Embodiment A] FIG. 1 shows an optical head portion of a first embodiment of an optical information recording / reproducing apparatus according to the present invention.

In FIG. 1, those functionally identical to those of the conventional example shown in FIG. 9 are designated by the same reference numerals. 21
Is a light source such as a semiconductor laser, 22 is a collimator lens, 2
3 is a beam shaping prism, 24 is an aperture for limiting the luminous flux, 25 is a diffraction grating as a light splitting element, 2
5'is a diffraction grating portion deposited on the diffraction grating 25, 101 is a diffraction grating (light splitting element) position adjusting mechanism, 26 is a polarization beam splitter, 27 is a quarter wavelength plate, 28 is an objective lens, 1 is an optical card. , 29 are spherical lenses, 30 is a cylindrical lens, and 31 is equivalent to the photodetector 31 shown in FIG. The process in which the light flux emitted from the light source 21 is transmitted through each optical section, reflected by the optical card 1 and guided to the photodetector 31 is the same as that shown in the conventional example, and therefore is omitted here.

By the way, the photodetector 3 of the optical head shown in FIG.
The position adjustment 1 is performed so that the light spot is arranged in the center of the four-division photodetector 31b of the photodetectors 31 shown in FIG. The diffraction grating 25 is removed in advance so that the positional adjustment of the photodetector 31 is not affected by the positional deviation of the diffraction grating 25.

The diffraction grating 25 is inserted into the optical head whose position of the photodetector 31 has been adjusted in this way, and is connected to the diffraction grating position adjusting mechanism 101. Next, the position of the diffraction grating 25 is adjusted, and during the adjustment, AF control is performed by the position-adjusted photodetector 31 so that the distance between the objective lens 28 and the optical card 1 is always kept constant and focusing is performed. Keep it in a state.

In this state, the diffraction grating position adjusting mechanism 101 moves the diffraction grating 25 with respect to the light beam in the direction of the light beam cross section. The light spot on the photodetector 31 at that time is
There is almost no movement, only the light intensity distribution inside the light spot changes. Utilizing this, each photodetector 31a,
The diffraction grating position adjusting mechanism 101 moves the diffraction grating 25 while observing the output changes of 31b and 31c.

It should be noted that the diffraction grating position adjusting mechanism 101 has a mechanism capable of moving the diffraction grating 25 two-dimensionally within the light beam cutting plane, and may be any mechanism that can move it in the light beam cutting plane XY direction. For example, there is push / pull with a screw as the moving means.

The output waveforms of the photodetectors 31a and 31c when the diffraction grating 25 is moved with respect to the light beam are shown in FIG.
2B shows the output waveform of the photodetector 31b. The horizontal axis of each figure is the diffraction grating portion 2 for the light beam.
The moving distance of 5 ', and the vertical axis represents the magnitude of output. The coincidence point is a point where the center of the light flux coincides with the center of the diffraction grating portion 25 '.

As can be seen from FIGS. 2-a and 2-b, when the diffraction grating portion 25 'does not exist for the light flux, there is no ± 1st-order diffracted light, and therefore the ± 1st-order diffracted light output level of FIG. Is 0, while the 0th-order diffracted light output level in FIG. 2-b is level c. Diffraction grating section 2 for light flux
As the 5 ′ gradually crosses, the ± 1st-order diffracted light output level in FIG. 2-a increases and the 0th-order diffracted light output level in FIG. 2-b decreases. Figure 2-a and Figure 2-b
Both have an extreme value in the output change, the ± 1st-order diffracted light output level in FIG. 2-a is the maximum value level a, and the 0th-order diffracted light output level in FIG. 2-b is the minimum value level b.

Next, the signals used for adjusting the diffraction grating position in this embodiment will be described with reference to FIGS.

First, FIG. 3 is a circuit diagram for producing a signal used for adjustment. In the figure, S1 to S4 are individual photodetectors of the quadrant photodetector 31b, 201 to 204 are input signal adder circuits, and 205 is an input signal differential circuit.

The adder circuits 201 and 202 add the detectors in the stacking direction of the four-division photodetector 31b.
The adder circuit 203 takes the sum of the outputs of the quadrant photodetectors. The output waveform of FIG. 2-b is the output waveform of this sum. Further, the output waveform of FIG. 2-a is the output waveform of the photodetector 31a or 31c.

In the circuit of FIG. 3, the output of the addition signal of the photodetectors 31a and 31c obtained by the addition circuit 204 and the addition circuit 2
The difference between the outputs of the four-division photodetector 31b obtained in step 03 is taken by the differential circuit 205. The signal waveform output from the differential circuit 205 is shown in FIG. That is, the differential circuit 20
When the output from No. 5 is represented by the output levels shown in FIGS. 2A to 2C, the level becomes D = 2a- (bc), which corresponds to 2 of the photodetector 31b.
It is possible to obtain an amplified signal that is four times that of the photodetector 31a or 31c. The position of the diffraction grating should be determined at the extreme value of the amplified signal, that is, the maximum value (minimum value depending on how the differential is taken).

That is, the position of the diffraction grating (light splitting element) is
The diffraction grating (light splitting element) position adjusting mechanism adjusts the position where the difference signal between the outputs of the auto-tracking photo detectors 31a and 31c and the output of the auto-focusing photo detector 31b has an extreme value. By holding it, the occurrence of offset can be eliminated.

In FIGS. 2-a and 2-b,
The absolute scale on the horizontal axis is determined by the diameter of the light beam and the diameter of the diffraction grating, and the absolute scale on the vertical axis is the output power of the light source, the film thickness of the diffraction grating, the transmission / reflectance of optical parts, the reflectance of the optical card, and the light detection. It is determined by the photoelectric conversion rate of the device.

In this embodiment, the integrated type optical head has been described, but it goes without saying that the same effect can be obtained by the same means also in a so-called separated type optical head which is divided into a movable portion and a fixed portion. Yes.

[Embodiment B] Another embodiment of the present invention will now be described in detail with reference to the drawings.

FIG. 1 shows an optical head portion of an embodiment of an optical information recording / reproducing apparatus according to the present invention. In FIG. 1, parts that are functionally the same as those of the conventional example and the above-described example are designated by the same reference numerals, and detailed description thereof is omitted.

The position of the photodetector 31 of the optical head shown in FIG. 1 is adjusted so that a light spot is arranged in the center of the four-divided photodetector 31b of the photodetectors 31 shown in FIG. . Note that the diffraction grating 25 is preliminarily set so that the positional adjustment of the photodetector 31 is not affected by the positional deviation of the diffraction grating 25.
Remove.

With respect to the optical head whose position is adjusted in the photodetector 31 as described above, the diffraction grating 25 as a light splitting element is provided.
And a diffraction grating (light splitting element) position adjusting mechanism 101
Connect to. Next, the position of the diffraction grating 25 is adjusted, and during the adjustment, AF control is performed by the position-adjusted photodetector 31 so that the distance between the objective lens 28 and the optical card 1 is always kept constant and focusing is performed. Keep it in a state.

In this state, the diffraction grating position adjusting mechanism 101 moves the diffraction grating 25 with respect to the light beam in the light beam cross-sectional direction. The light spot on the photodetector 31 at that time is
There is almost no movement, only the light intensity distribution inside the light spot changes. Utilizing this, the diffraction grating position adjusting mechanism 101 moves the diffraction grating 25 so that the respective output changes of the four-division photodetector 31b for autofocusing and information reproduction become equal.

The diffraction grating position adjusting mechanism 101 is a mechanism that allows the diffraction grating 25 to move two-dimensionally within the plane of the light beam, and is any mechanism that can move the light in the plane XY direction within the cross section of the light beam. Well, for example, push and pull with a screw as the moving means.

Further, in the present embodiment, the description has been made on the integrated type optical head, but it is needless to say that the same effect can be obtained by the same means also in a so-called separated type optical head which is divided into a movable portion and a fixed portion. Yes.

[Embodiment C] Another embodiment of the present invention will now be described in detail with reference to the drawings.

FIG. 1 shows an optical head portion of an embodiment of an optical information recording / reproducing apparatus according to the present invention. In FIG. 1, parts that are functionally the same as those of the conventional example and the above-described example are designated by the same reference numerals, and detailed description thereof is omitted.

The position of the photodetector 31 of the optical head shown in FIG. 1 is adjusted so that a light spot is arranged in the center of the four-divided photodetector 31b of the photodetectors 31 shown in FIG. . The diffraction grating 25 is removed in advance so that the positional adjustment of the photodetector 31 is not affected by the positional deviation of the diffraction grating 25 as a light splitting element.

The diffraction grating 25 is inserted into the optical head whose position is adjusted by the photodetector 31 in this way, and is connected to the diffraction grating (light splitting element) position adjusting mechanism 101. Next, the position of the diffraction grating 25 is adjusted, and during the adjustment, AF control is performed by the position-adjusted photodetector 31 so that the distance between the objective lens 28 and the optical card 1 is always kept constant and focusing is performed. Keep it in a state.

In this state, the diffraction grating position adjusting mechanism 101 moves the diffraction grating (light splitting element) 25 in the beam cross section direction. The light spot on the photodetector 31 at that time hardly moves, and only the light intensity distribution inside the light spot changes. Utilizing this, each photodetector 31
The diffraction grating 25 is moved by the diffraction grating position adjusting mechanism 101 while observing the output changes of a, 31b and 31c.

The diffraction grating position adjusting mechanism 101 is a mechanism capable of moving the diffraction grating 25 two-dimensionally within a plane of the light beam, and may be any mechanism that can move the diffraction grating 25 in the plane XY direction in the light beam cross section. For example, there is push / pull with a screw as the moving means.

The output waveforms of the photodetectors 31a and 31c when the diffraction grating 25 is moved with respect to the light beam are shown in FIG.
2B shows the output waveform of the photodetector 31b. The horizontal axis of each figure is the diffraction grating portion 2 for the light beam.
The moving distance of 5 ', and the vertical axis represents the magnitude of output. The coincidence point is a point where the center of the light flux coincides with the center of the diffraction grating portion 25 '.

As can be seen from FIGS. 2-a and 2-b, when the diffraction grating portion 25 'does not exist for the light flux, there is no ± 1st-order diffracted light, so the ± 1st-order diffracted light of FIG. The output level is 0, while the 0th-order diffracted light output level in FIG. 2B is level c. As the diffraction grating portion 25 'gradually crosses the light beam, the ± first-order diffracted light output level in FIG. 2-a increases and the 0th-order diffracted light output level in FIG. 2-b decreases. 2A and 2 at the point of coincidence.
Both -b have an extreme value in the output change, the ± 1st order diffracted light output level in FIG. 2-9 is the maximum value level a, and the 0th order diffracted light output level in FIG. 2b is the minimum value level b.

That is, in the diffraction grating position adjustment in the present embodiment, at the point where the signal output of any of the photodetectors 31a, 31b, 31c shown in FIG. 4 takes an extreme value (maximum value or minimum value). It is sufficient to determine the position of the diffraction grating.

This is, for example, a diffraction grating (light splitting element).
Need only be adjusted and held at a position where the output value of the auto-tracking photodetector takes the maximum value, and for the diffraction grating (light splitting element), the output value of the autofocusing photodetector takes the minimum value. It may be adjusted and held in position.

In FIGS. 2-a and 2-b,
The absolute scale on the horizontal axis is determined by the diameter of the light beam and the diameter of the diffraction grating, and the absolute scale on the vertical axis is the output power of the light source, the film thickness of the diffraction grating, the transmission / reflectance of optical parts, the reflectance of the optical card, and the light detection. It is determined by the photoelectric conversion rate of the device.

In this embodiment, the integrated optical head has been described, but it goes without saying that the same effect can be obtained by the same means also in a so-called separated optical head which is divided into a movable portion and a fixed portion.

[0065]

【The invention's effect】

[Effect A] As described above, according to the present invention, in the optical information recording / reproducing apparatus having the optical head using the diffraction grating having a diameter smaller than the diameter of the light beam incident on the diffraction grating, The difference between the output of the detector and the output of the photodetector for auto-focusing and reproduction takes an extreme value, and the diffraction grating is moved with respect to the luminous flux, and the position is determined, so that the offset of AT and AF control is reduced. Thus, it is possible to provide an optical information recording / reproducing apparatus which can always perform stable control.

[Effect B] Further, according to the present invention, in the optical information recording / reproducing apparatus having the optical head using the diffraction grating having a diameter smaller than the diameter of the light beam incident on the diffraction grating,
By moving and positioning the diffraction grating with respect to the light flux so that the respective outputs of the four-division photodetectors for autofocusing and reproduction become equal, it is possible to achieve stable control without offset in AT and AF control. It is possible to provide an optical information recording / reproducing device that can be performed.

[Effect C] Further, according to the present invention, in the optical information recording / reproducing apparatus having the optical head using the diffraction grating having a diameter smaller than the diameter of the light beam incident on the diffraction grating,
By moving and positioning the diffraction grating with respect to the light flux so that one of the outputs of the photodetector takes an extreme value, optical information that can be always stably controlled without offset in AT and AF control. A recording / reproducing device can be provided.

[Brief description of drawings]

FIG. 1 is a diagram showing an optical arrangement of an optical head portion of an optical information recording / reproducing apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing an output level of each photodetector.

FIG. 3 is a circuit diagram for generating an adjustment signal used in this embodiment.

FIG. 4 is a diagram showing a positional relationship between a configuration of a photodetector and a light spot.

FIG. 5 is a diagram showing a positional relationship between a light beam incident on a diffraction grating and a diffraction grating portion.

FIG. 6 is a diagram showing a light intensity distribution on a cross section of a light beam in a conventional example.

FIG. 7 is a schematic view of an optical card.

FIG. 8 is a partially enlarged view of the optical card, showing a positional relationship with an irradiation spot.

FIG. 9 is an optical layout diagram of a conventional optical head.

[Explanation of Codes] 1 Optical Card 21 Light Source 22 Collimator Lens 23 Beam Shaping Prism 24 Aperture 25 Diffraction Grating 25 'Diffraction Grating Part 26 Polarizing Beam Splitter 27 1/4 Wave Plate 28 Objective Lens 29 Spherical Lens 30 Cylindrical Lens 31 Photo Detector 31a, 31c AT control photodetector 31b AF control and reproduction photodetector 101 Diffraction grating position adjusting mechanism 201-204 Adder circuit 205 Differential circuit

Claims (17)

[Claims] 1. An aperture for limiting a light beam emitted from a light source, a light splitting element for splitting the light beam limited by the aperture into a plurality of light beams, and an optical for converging the plurality of light beams as a minute spot on an optical information recording medium. A system, and a detection optical system for guiding the reflected light from the optical information recording medium to a photodetector for auto-tracking and a plurality of divided photodetectors including a photodetector for autofocusing. An optical information recording / reproducing apparatus including an optical head having the optical dividing element position adjusting means for adjusting the position of the optical dividing element, wherein the position of the optical dividing element is the optical dividing element position adjusting mechanism. By the output of the photodetector for auto-tracking,
An optical information recording / reproducing apparatus, wherein the difference signal from the output of the photodetector for autofocusing is adjusted and held at a position where it takes an extreme value. 2. The optical information recording / reproducing apparatus according to claim 1, wherein the light splitting element is a diffraction grating having an area equal to or smaller than a cross-sectional area of a light beam limited by the aperture. 3. The optical information recording / reproducing apparatus according to claim 2, wherein the diffraction grating has a circular shape. 4. The optical information recording / reproducing apparatus according to claim 1, wherein an output of the photodetector for auto-tracking is a sum of signals from at least one photodetector. 5. The optical information recording / reproducing apparatus according to claim 1, wherein an output of the photodetector for autofocusing is a signal sum from at least one photodetector. 6. The optical information recording / reproducing apparatus according to claim 1, wherein the light splitting element position adjusting mechanism moves the light splitting element within a light beam cross section. 7. An aperture for limiting a light beam emitted from a light source, a light splitting element for splitting the light beam limited by the aperture into a plurality of light beams, and an optical for converging the plurality of light beams as a minute spot on an optical information recording medium. A system, and a detection optical system for guiding the reflected light from the optical information recording medium to a photodetector for auto-tracking and a plurality of divided photodetectors including a photodetector for autofocusing. An optical information recording / reproducing apparatus having an optical head having an optical dividing element position adjusting mechanism for adjusting the position of the optical dividing element, and outputs of each of the plurality of divided photodetectors for autofocusing. An optical information recording / reproducing apparatus characterized in that the light splitting element is adjusted and held by the light splitting element position adjusting mechanism at a position where they are equal to each other. 8. The optical information recording / reproducing apparatus according to claim 7, wherein the light splitting element is a diffraction grating having an area equal to or smaller than a cross-sectional area of the light beam limited by the aperture. 9. The optical information recording / reproducing apparatus according to claim 8, wherein the diffraction grating has a circular shape. 10. The optical information recording / reproducing apparatus according to claim 7, wherein the photodetector for autofocusing is a photodetector divided into four parts. 11. The optical information recording / reproducing apparatus according to claim 7, wherein the light splitting element position adjusting mechanism moves the light splitting element within a light beam cross section. 12. An aperture for limiting a light flux emitted from a light source, a light splitting element for splitting the light flux limited by the aperture into a plurality of light fluxes, and an optical for converging the plurality of light fluxes as a minute spot on an optical information recording medium. A system, and a detection optical system for guiding the reflected light from the optical information recording medium to a photodetector for auto-tracking and a plurality of divided photodetectors including a photodetector for autofocusing. In an optical information recording / reproducing apparatus including an optical head having, a light dividing element position adjusting mechanism for adjusting the position of the light dividing element is provided, wherein the light dividing element is a plurality of divided photodetectors. An optical information recording / reproducing apparatus, characterized in that it is adjusted and held by the light splitting element position adjusting mechanism at a position where any of the output values has an extreme value. 13. The optical information recording / reproducing apparatus according to claim 12, wherein the light splitting element is a diffraction grating having an area equal to or smaller than a cross-sectional area of a light beam limited by the aperture. 14. The optical information recording / reproducing apparatus according to claim 13, wherein the diffraction grating has a circular shape. 15. The optical information recording / reproducing apparatus according to claim 12, wherein the light splitting element is adjusted and held at a position where the output value of the auto-tracking photodetector takes a maximum value. 16. The optical information recording / reproducing apparatus according to claim 12, wherein the light splitting element is adjusted and held at a position where an output value of the autofocusing photodetector has a minimum value. 17. The optical information recording / reproducing apparatus according to claim 12, wherein the light splitting element position adjusting mechanism moves the light splitting element within a light beam cross section.