JP3500158B2 - Light head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] The present invention relates to an optical recording medium.
Optical head for recording and / or reproducing information
About [0002] 2. Description of the Related Art As a conventional optical head, an optical system is simplified.
The use of hologram elements for miniaturization, miniaturization, etc.
Various proposals have been made. For example, JP-A-62-27763
No. 5 proposes an optical head shown in FIG. [0003] In the optical head shown in FIG.
The light from the laser 1 is incident on the grating lens 2 and its 0th order light
Is projected onto the recording medium 4 via the imaging lens 3 and the reflected light
(Return light) is incident on the grating lens 2 through the imaging lens 3.
And the diffracted light is received by the photodetector 5.
You. The grating lens 2 is a line intersecting the optical axis of the semiconductor laser 1.
Pupil with different diffraction directions from 6 and 7
It has four divided lens areas 2a to 2d.
The return light from the recording medium 4 is diffracted in the
I am trying to. The photodetector 5 has six light receiving areas.
It is configured with a six-segment element having regions 5a to 5f,
The light diffracted by the lens area 2a of the secondary lens 2
5a, the light diffracted by the lens area 2b is received by the light receiving area 5b.
The light diffracted by the lens area 2c is received by the light receiving areas 5c and 5c.
d, the light diffracted by the lens region 2d is converted into the light receiving region 5e,
Each light is received at 5f. Note that the grid
The focal length of each lens area 2a to 2d of the lens 2
In the areas 2a and 2b, they are equal, and in the lens areas 2c and 2d,
The focal position of the lens areas 2a, 2b
I have. In such an optical head, the light receiving area 5
c, 5d and the light receiving areas 5e, 5f
When the recording medium 4 is in focus, the incident light intensity
Are arranged so that
Based on the outputs of the areas 5c and 5d and the light receiving areas 5e and 5f
Focus error signal of the imaging lens 3 with respect to the recording medium 4
And track based on the outputs of the light receiving areas 5a and 5b.
To obtain a switching error signal. [0005] However, as described above,
In the conventional optical head, the semiconductor laser 1 and the light detection
Miniaturization because the container 5 is arranged separately
However, there is a problem that it is difficult to achieve. Also, grating lens 2
Is the diffraction angle of each of the four lens regions 2a to 2d.
Because it is necessary to make it different, its production is not easy,
There is a problem that the cost is increased. The present invention addresses such a conventional problem.
It was made with the aim of making it compact, easy and inexpensive.
It is an object of the present invention to provide an optical head that can be manufactured at a low price. [0007] The present invention achieves the above object.
An optical head according to the invention includes a semiconductor substrate and a semiconductor substrate.
Having a concave slope and a semiconductor mounted in the recess
A laser and a laser beam emitted from the semiconductor laser.
Focusing means for focusing the emitted light on an optical recording medium;
Hologram for diffracting return light from an optical recording medium
An element and the hologram formed on the surface of the semiconductor substrate;
Receiving the first order diffracted light of the return light diffracted by the ram element
A track for the optical recording medium of the condensing means.
Photodetector for detecting a switching error signal and the semiconductor
In order to control the output of the laser,
A monitor formed on the semiconductor substrate to receive the emitted light
A photodetector for the optical detector, wherein the photodetector is
Parallel to the above slope in a direction parallel to the recording track direction of the recording medium.
And the photodetector has the recording track.
Dividing by a dividing line parallel to the direction to provide a plurality of light receiving areas,
The monitor photodetector is almost aligned with the recording track direction.
Formed alongside the semiconductor laser in a direction orthogonal to
In the hologram element, the grating direction is almost the same as the recording track direction.
Formed in a direction substantially perpendicular to the hologram element.
The write-back light is diffracted in a direction parallel to the recording track direction.
It is characterized in that it is configured to allow [0008] In this configuration, the light from the semiconductor laser is
Is reflected by the slope of the concave part of the semiconductor substrate on which it is mounted.
And is condensed on the optical recording medium through the condensing means.
The reflected light (return light) on the optical recording medium is a hologram element.
Is diffracted in the direction parallel to the recording track direction by the
The first-order diffracted light is inclined in a direction parallel to the recording track direction.
It is formed on the semiconductor substrate alongside the surface,
With a photodetector having a light receiving area divided by parallel dividing lines
The optical recording medium of the light condensing means is received based on the output.
A tracking error signal for the body is detected. Also,
The light from the semiconductor laser is almost perpendicular to the recording track direction
Formed on a semiconductor substrate alongside the semiconductor laser in the direction
Received by the monitoring photodetector and based on the output
The output of the semiconductor laser is controlled. [0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 and FIG.
FIG. 1 shows a configuration of a first reference example of an optical head according to the present invention.
FIG. 2 shows a sectional view. This optical head uses magneto-optical
Recording and / or reproducing information on the recording medium 25
The laser unit 12 and the hollow
Gram element 13 and objective lens 14
The holder 11 is moved to the magneto-optical recording medium 2 by a known electromagnetic driving means.
5, the focus direction (Z direction) and the
And a track that intersects the track 26 of the magneto-optical recording medium 25.
Drive in two directions, the locking direction (X direction).
You. The laser unit 12 is provided with a silicon substrate 15.
Then, a semiconductor laser 16 is mounted on the silicon substrate 15.
And five photodetectors 17 to 21 are formed on the surface.
To achieve. In addition, on the silicon substrate 15,
A V-shaped groove 15a is formed from the
2 with its end face inclined at 45 ° to the silicon substrate 15
To fix the position. Semiconductor laser with parallel plate 22
A half mirror coat is applied to the surface 22a on the 16 side,
The opposite surface 22b has an X direction (the direction orthogonal to the track).
For polarization separation having a grating in the 45 ° direction as viewed from
A program 23 is formed. The photodetector 17 is located behind the semiconductor laser 16.
The semiconductor laser 1 is configured to receive a part of the lower side of the emitted light.
6 on the X direction (-) side, and based on its output,
The power of the body laser 16 is controlled. Also light
The detectors 18 and 19 are located on the X direction (+) side of the parallel plate 22.
And the photodetector 19 is divided into two parts in the X direction.
It comprises optical regions 19a and 19b. In addition, optical inspection
The output devices 20 and 21 are formed on both sides of the parallel plate 22 in the Y direction.
You. These photodetectors 20 and 21 are respectively in the X direction.
6 light receiving areas 20 divided into 3 and two in the Y direction
a to 20f and 21a to 21f. The hologram element 13 is formed by
The hologram element 13 is arranged in the direction (+)
The objective lens 14 is arranged on the direction (+) side. Hologram element
The element 13 has a lattice substantially parallel to the X direction on its surface 13a.
Separate holograms 24a and 24b in the Y direction
Formed. In FIG. 1, the objective lens 14 is
The silicon substrate 15 and the like are exaggerated and drawn large. Hereinafter, the operation of the optical head will be described. Half
The light emitted to the X direction (−) side of the conductor laser 16 is
A part of the lower side enters the photodetector 17, and this photodetector 17
Control circuit (not shown) based on the output of
The output of the user 16 is controlled. In addition, the semiconductor laser 16
The light emitted in the X direction (+) is polarized parallel to the Y direction.
Incident on the half mirror surface 22a of the parallel plate 22
Part of which is reflected in the Z direction (+),
Magneto-optical recording medium via a system element 13 and an objective lens 14
25 as a light spot on 25 recording tracks 26
You. In this optical head, a light spot is formed.
The tangential direction of the recording track 26 at the portion to be
The row is parallel to the polarization direction of the irradiation light. The reflected light (return light) from the recording medium 25 is
And enters the hologram element 13 via the objective lens 14.
You. Here, the recording pits or grooves of the recording medium 25
Return light 27 which is diffracted by the light and enters the hologram element 13
Light intensity fluctuation mainly appears in the X direction,
Hologram 24 formed on surface 13a of system element 13
a and 24b are located on both sides of the return light 27 in the Y direction.
Therefore, in the X direction due to diffraction at the recording pit or groove
Of light intensity fluctuations. These holograms 24
a, the ± 1st order diffracted light of the return light 27 diffracted by 24b
The light enters the photodetectors 20 and 21, respectively. Photodetector 20
From the hologram 24b and the photodetector 2
The light from the hologram 24a incident on 1 is focused behind.
Connect, but from the hologram 24a incident on the photodetector 20
Light and the hologram 24b incident on the photodetector 21
These lights focus in the foreground. Therefore, the photodetector 20
Output of the light receiving areas 20a to 20f of S_20a~ S_20e
 The output of the light receiving areas 21a to 21f of the photodetector 21 is S
_21a~ S_20e, The focus error signal (F
E) can be obtained from the following equation by the beam size method.
Can be. FE = (S_20a-S_20b+ S_20c)-
(S_20d-S_20e+ S_20f)-(S_21a-S
_21b+ S_21c) + (S_21d-S_21e+
S_21f) The hologram 24 of the return light 27
a, and the holograms 24a,
The light that has entered other than 24b is again reflected by the half of the parallel plate 22.
The half mirror surface 22a is incident on the mirror surface 22a.
The transmitted light enters the hologram 23. Here,
The grating direction of the program 23 is relative to the polarization direction of the return light.
The hologram 23 forms an angle of approximately 45 °.
The + 1st-order diffracted light of the polarization-separated return light is converted to a light detector 18.
Then, the zero-order light enters the photodetector 19. Therefore, light
The output of the light receiving areas 19a and 19b of the detector 19 is
S_19a, S_19bAnd the tracking error signal
(TE) is obtained from the following equation by the push-pull method.
Can be ## EQU2 ## TE = (S_19a-S_19b) Further, the magneto-optical signal (RF) outputs the output of the photodetector 18 to S
₁₈Can be obtained by the following equation. ## EQU3 ## RF = (S_19a+ S_19b) -S₁₈ According to this optical head, the recording track 26
And the direction of the recording track 26 (Y direction).
And the direction of the push-pull signal
Can be higher. Therefore, the tracking error signal (T
F) has high sensitivity and high precision without being affected by noise.
Can be detected in degrees. Also, the photodetectors 20, 21
Light incident on the magneto-optical recording medium 25
Is less susceptible to the influence of X-rays in the X direction.
The division line directions of the light receiving areas 0 and 21 are defined as recording tracks 26.
Tracking error despite parallel orientation
Generate crosstalk and light intensity fluctuations with the difference signal (TE)
Hard to repel. Therefore, the focus error signal (FE)
With high sensitivity and high accuracy without being affected by noise
Can be detected. Also, in the return light path,
A hologram 2 for detecting a magneto-optical signal is provided on a surface 22b of the flat plate 22.
Since hologram 23 is formed integrally, hologram 23 can be reduced in size.
In addition, the configuration can be simplified. Further, magneto-optical recording is performed from the semiconductor laser 16.
Only part of the light traveling toward the medium 25 is the hologram 24.
a, 24b diffracted light, the light utilization effect on the outward path
And the light intensity on the magneto-optical recording medium 25 can be increased.
The degree can be raised. Therefore, the magneto-optical signal (RF) is high.
It can be detected with sensitivity. Also, the photodetectors 20, 2
1 is arranged in a direction orthogonal to the light emitted from the semiconductor laser 16.
Light emitted from the front and rear of the semiconductor laser 16
Does not enter, and therefore offsets etc. occur
Never. A semiconductor laser is provided on the silicon substrate 15.
16, the photodetectors 17 to 21 and the parallel plate 22 are integrated
The laser unit 12 was constructed by
Can be shaped. Furthermore, the light receiving areas of the photodetectors 20, 21
The direction of the area dividing line is parallel to the Y direction, and the hologram 24
a, the same as the diffraction direction of the first order diffraction by 24b
Change in diffraction angle due to wavelength fluctuation of the semiconductor laser 16
Not affected by In addition, the tracking error signal (T
E) shows holograms 24a and 24b and hologram 2
Since the zero-order light of No. 3 is used, the wave of the semiconductor laser 16 is
Unaffected by length fluctuations. Also, the hologram element 13
Of the incident return light 27, only the ± 1st-order diffracted light is required.
And the zero-order light is used, so that the return light 27
Can improve the efficiency of use. Further, of the return light 27, the hologram 2
4a and 24b received by the photodetectors 20 and 21.
Detects focus error signal (FE) by illuminating
0th order light of the holograms 24a and 24b and the holograms 24a and 2
4b is received by the photodetector 19 and tracked.
Error signal is detected, that is, separate
Focus error signal (FE) and track by photodetector
Error signal is detected, so that each photodetector
Set the direction of the dividing line and the diffraction direction to the optimal direction.
Can be. Further, the semiconductor laser 16 is mounted on the shell.
Outgoing light is reflected by the parallel plate 22 on the recon board 15
And photodetectors 19, 20, 21 for error signal detection
The direction of the dividing line of each light receiving area
Since the laser was aligned in the Y direction orthogonal to the emission axis,
16 is displaced with respect to the silicon substrate 15 in the Y direction.
Can cause an offset in the error signal.
Absent. Further, ± 1 order by holograms 24a and 24b
Do not allow diffracted light to enter the hologram 23 for polarization separation
And the zero-order light and the holograms 24a, 24b
Since only light that does not pass through is made incident, semiconductor
Even if the wavelength of the laser 16 fluctuates, a hologram for polarization separation is used.
The incident angle of the light incident on the ram 23 does not change. Accordingly
Polarization separation can always be performed accurately,
A magneto-optical signal (RF) can be obtained. FIG. 3 is a perspective view showing an embodiment of the present invention.
It is. In FIG. 3, members that perform the same operations as those in FIG.
Are denoted by the same reference numerals, and description thereof is omitted. This example
Then, the slope 15 is formed on the silicon substrate 15 by etching or the like.
b is formed, and a semiconductor is formed in the recess 15c.
The body laser 16 is mounted, and the emitted light is
Reflected in the Z (+) direction, ie, toward the hologram element 13
Let it. In addition, in order to raise a reflectance, the slope 15b is provided.
Is coated with, for example, gold. Also, the slope 15b
On the silicon substrates 15 on both sides in the Y direction,
Light receiving areas 31a, 31b and 32a, 32 divided into two parts
b, forming photodetectors 31 and 32 having
Outside of the photodetectors 31 and 32, each divided into three in the X direction
Light receiving areas 33a, 33b, 33c and 34a, 3
The photodetectors 33 and 34 having 4b and 34c are formed.
Further, the hologram element 13 is returned to its surface 13a.
The hologram 24 is obtained by pupil-dividing both ends of the reflected light 27 in the Y direction.
a, 24b, and the hologram 2
4c is formed. The holograms 24a, 24b and
And 24c are substantially parallel to the X direction.
You. In such a configuration, the magneto-optical recording medium 25
Returning light 27 from the surface 13a of the hologram element 13
Is diffracted by the holograms 24a and 24b, and ± 1 next time
The folded light enters the photodetectors 33 and 34. Where the light detection
Light incident on the detector 33 is focused in front,
34, the light incident on the back focuses on the objective lens 1
4 is focused on the magneto-optical recording medium 25
Is the size of the spot formed on the photodetectors 33 and 34.
Are equal. Therefore, the light receiving area of the photodetector 33
The outputs of 33a, 33b, 33c are S_33a, S_33b,
S_33cLight receiving areas 34a, 34b, 3 of the photodetector 34
Output of 4c to S_34a, S_34b, S_34cThen
And the focus error signal (FE) is calculated by the following equation.
Can be FE = (S_33a-S_33b+ S_33c)-
(S_34a-S_34b+ S_34c) Further, ± 1 diffracted by the hologram 24c
The next-order diffracted light enters the photodetectors 31 and 32. here,
The light incident on the photodetector 31 is focused in front,
Light incident on the detector 32 is focused behind. But
Thus, the outputs of the light receiving areas 31a and 31b of the photodetector 31 are
S_31a, S_31b, The light receiving area 32a of the photodetector 32,
32b output is S_32a, S_32bWhen
The King error signal (TE) is calculated by the push-pull method
It can be obtained by the following equation. ## EQU5 ## TE = (S_31a-S_31b)-(S_32a−
S_32b) Further, the objective lens is
The laser 14 is displaced in the X direction or the magneto-optical recording medium
When 25 is tilted around the Y axis, it returns to the hologram 13
The reflected light 27 moves in the X direction, thereby causing the photodetectors 31,
The light beam incident on 32 also moves in the X direction,
An offset occurs in the error signal (TE). In this case,
The distribution of the amount of light in the X direction incident on the programs 24a and 24b is also
Since it changes, as an offset signal (TO),
If ## EQU6 ## TO = (S_33a-S_33c) , The amount of movement of the return light 27 in the X direction can be obtained.
it can. Therefore, this offset signal (TO) is used.
And ## EQU7 ## TE ′ = TE−k · TO Is calculated, the tracking error corrected for the offset
The signal TE 'can be obtained. Note that in Equation 7,
k indicates a correction coefficient. Thus, the photodetectors 33, 34
Incident on the pits and glues of the magneto-optical recording medium 25.
The output is turned off because it is less susceptible to diffraction
It can be used for set correction. According to this embodiment, FIGS.
In addition to the effects in the optical head, the photodetectors 33, 3
4 can be constituted by three divided light receiving areas.
Thus, wiring, a preamplifier, and the like become easy. Also, track
Offset of the error signal (TE) can be corrected,
Stable tracking servo can be applied. Sa
And a light for detecting a focus error signal (FE).
The bundle is formed by pits and grooves on the magneto-optical recording medium 25.
Since it is hardly affected by diffraction in the X direction, tracking error
Light beam for detecting difference signal and light for detecting focus error signal
The light is diffracted in the same direction as the
Dividing lines for each light receiving area of the output units 31, 32, 33 and 34 are set.
Can be specified. Therefore, the semiconductor laser 16
It is not affected by the change in the diffraction angle due to the wavelength change. FIG. 4 shows an optical head developed with the present invention.
FIG. 9 is a perspective view showing a configuration of a second reference example of the present invention. Figure 4
Therefore, members performing the same operations as those in FIG.
And the description is omitted. In this reference example, the semiconductor laser
The photodetector 3 is provided on the silicon substrate 15 on both sides of the laser 16 in the Y direction.
5 and 36, and Y direction on both sides in the X direction
Light receiving areas 37a, 37b, 37c and 3 divided into three
8a, 38b, and 38c are provided.
I can. The hologram element 13 has a surface 13a.
The Y direction parallel to the groove direction of the magneto-optical recording medium 25
Holograms 39a, 39
b, 39c are formed. Here, the intermediate hologram 39
a, the lattice is formed substantially parallel to the Y direction,
Programs 39b and 39c are blazed and their case
The element is formed substantially parallel to the X direction. In such a configuration, the hologram element 13
Return light 27 from the magneto-optical recording medium 25
The ± 1st-order diffracted light diffracted by the hologram 39a is light
The light enters the detectors 37 and 38. Here, the photodetector 37
The incident light is focused in front, but enters the photodetector 38.
The emitted light is focused behind and the objective lens 14
When the air recording medium 25 is in focus, light detection
Spots formed on the vessels 37 and 38 are equal in size
Become. Therefore, the light receiving regions 37a, 3a of the photodetector 37
Output of 7b and 37c is S_37a, S_37b, S_37c,
Output of light receiving areas 38a, 38b, 38c of photodetector 38
S_38a, S_38b, S_38cWhen you focus
Error signal (FE) is obtained by the following beam size method.
It can be obtained by an equation. FE = (S_37a-S_37b+ S_37c)-
(S_38a-S_38b+ S_38c) Also, the blazed hologram 39
b and 39c, respectively, and are separated from the 0th order light,
Of the + 1st-order diffracted light, the + 1st-order diffracted light is a photodetector
It is incident on 35 and 36. Therefore, the output of the photodetector 35 is
Power S₃₅, The output of the photodetector 36 is S₃₆When
The tracking error signal (TE) is calculated by the push-pull method.
It can be obtained by the following equation. ## EQU9 ## TE = (S₃₅-S₃₆) According to this reference example, the effect of the above-described embodiment can be obtained.
In addition, there are the following effects. That is, the track
Error signal (TE) is the X direction perpendicular to the groove.
+1 order in the holograms 39b and 39c divided in the pupil direction
The diffracted lights are received by different photodetectors 35 and 36, respectively, and detected.
The size of the photodetectors 35 and 36
To be large enough for the incident spot.
it can. Therefore, the positioning and positioning of the photodetectors 35 and 36 are
And the hologram element 13 can be easily positioned in the X direction.
Yes, assembling is easy as a whole. And e
The programs 39b and 39c are blazed, -1 next time
Since there is no folded light, the amount of light incident on the photodetectors 35 and 36 is large.
I can take it. In addition, the two photodetectors 35 and 36
King error signal (TE) can be detected.
Hologram 39
b and 39c are not necessarily the cases of the blazed diffraction grating.
Since it is not necessary to make the element direction parallel to the X direction,
By changing the grid direction of
Can be arranged freely, increasing the degree of freedom of configuration
it can. Further, the focus error signal (FE) is detected.
The light detectors 37 and 38 for emitting light are arranged in the direction of the groove.
Since it is divided by a dividing line parallel to the X direction perpendicular to
Part where spot change is large when out-of-focus occurs
Is positioned on the dividing line of each photodetector 37, 38
Can be. Therefore, the focus error signal (FE) is
It can be detected with high sensitivity. FIG. 5 shows an optical head developed with the present invention.
FIG. 13 is a perspective view illustrating a configuration of a third reference example of the hand. Figure 5
Therefore, members performing the same operations as those in FIG.
And the description is omitted. In this reference example, the hologram
4 around the optical axis of the return light 27 on the surface 13a of the element 13.
Holograms 41a to 41d are formed by division. here
The holograms 41a and 41b facing each other in the Y direction are
These gratings are aligned with the groove direction of the magneto-optical recording medium 25.
Holograms formed in roughly parallel Y direction and opposed in X direction
41c and 41d are blazed and their grids are roughly
It is formed parallel to the direction X. In such a configuration, the hologram element 13
Return light 27 from the magneto-optical recording medium 25
± 1st order diffraction diffracted by holograms 41a and 41b
Light enters the photodetectors 37 and 38. Where the light detection
The light incident on the detector 37 is focused in front, but the light detector
The light incident on the lens 38 is focused rearward and the objective lens 1
4 is focused on the magneto-optical recording medium 25
Is the size of the spot formed on the photodetectors 37 and 38.
Are equal. Therefore, the light receiving area of the photodetector 37
The outputs of 37a, 37b and 37c are S_37a, S_37b,
S_37c, Light receiving areas 38a, 38b, 3 of the photodetector 38
8c output_38a, S_38b, S_38cThen
The focus error signal (FE) is calculated using the beam size method.
Thus, it can be obtained from the above equation (8). Also, the blazed hologram 41
0th order light which is incident on c and 41d and separated respectively, and
Of the + 1st-order diffracted light, the + 1st-order diffracted light is a photodetector
It is incident on 35 and 36. Therefore, the output of the photodetector 35 is
Power S₃₅, The output of the photodetector 36 is S₃₆When
The tracking error signal (TE) is calculated by the push-pull method.
Therefore, it can be obtained by the above equation (9). According to this reference example, the effect of the above-described embodiment is obtained.
In addition to the fruits, there are the following effects. That is, the push
Out of the luminous flux including the double signal, the focus error signal (F
E) Since there are few parts used for detection,
Double signal can be detected without loss.
Detects tracking error signal (TE) with higher sensitivity
be able to. FIG. 6 shows an optical head developed with the present invention.
FIG. 14 is a perspective view illustrating a configuration of a fourth reference example of the present invention. Figure 6
Therefore, members performing the same operations as those in FIG.
And the description is omitted. In this reference example,
On the plate 15, each of 45 ° to the X and Y directions
Photodetectors 51a to 51a on both sides of the semiconductor laser 16 in the direction.
1d is provided. Also, the surface 13a of the hologram element 13
Is divided into four holograms around the optical axis of the return light 27
52a to 52d are formed. Here, it faces in the Y direction
The holograms 52a and 52b record their gratings magneto-optically.
Formed in the Y direction substantially parallel to the groove direction of the recording medium 25
The holograms 52c and 52d facing in the X direction are
Tilt these gratings ± 45 ° with respect to the Y direction and orthogonal to each other
In the direction of In such a configuration, the hologram element 13
Return light 27 from the magneto-optical recording medium 25
± 1st-order diffraction diffracted by holograms 52a and 52b
Light enters the photodetectors 37 and 38. Where the light detection
The light incident on the detector 37 is focused in front, but the light detector
The light incident on the lens 38 is focused rearward and the objective lens 1
4 is focused on the magneto-optical recording medium 25
Is the size of the spot formed on the photodetectors 37 and 38.
Are equal. Therefore, the light receiving area of the photodetector 37
The outputs of 37a, 37b and 37c are S_37a, S_37b,
S_37c, Light receiving areas 38a, 38b, 3 of the photodetector 38
8c output_38a, S_38b, S_38cThen
The focus error signal (FE) is calculated using the beam size method.
Thus, it can be obtained from the above equation (8). Further, ± 1 diffracted by the hologram 52c
The second-order diffracted light enters the photodetectors 51a and 51b,
The ± 1st order diffracted light diffracted by the ram 52d is
c, 51d. Therefore, the photodetectors 51a to 51a to
51d output is S_51a~ S_51dWhen
The King error signal (TE) can be obtained by the following equation.
Can be. ## EQU10 ## TE = (S_51a+ S_51b)-(S_51c
+ S_51d) According to this reference example, the tracking error signal
Holograms 52c and 52d for detecting signal (TE)
Hologram 13 is easy because it is not necessary to blaze
And it can be inexpensive. Also, the photodetectors 51a to 51d
To change the grid direction of the holograms 52c and 52d
It can be arranged more freely, so the degree of freedom of configuration will increase
Has the effect. In the above description, the hologram element
13 are provided independently, but the hologram element 13 and the objective lens
To reduce the number of parts
it can. FIG. 7 shows the holograms 24a and 24 shown in FIGS.
An example in which b is formed integrally with the objective lens 14 is shown. This
The hologram element 13 and the objective lens 14 are integrated
In this case, the objective lens 14 is made of plastic or
When forming a glass molded product or using the objective lens 14
The hologram is formed on the surface by applying
Can be achieved. The present invention also provides a magneto-optical recording medium.
Optical head for recording and / or reproducing information from the body
Recording information on other optical recording media
And / or to an optical head that performs reproduction.
Can be. 1 and 2, a parallel plate 22 is used.
However, a prism could be used instead.
You. In FIG. 3, the tracking error signal is off.
The offset is applied to the light receiving areas 33a and 33c of the photodetector 33.
Corrected using force, but received by photodetectors 33 and 34
Using the outputs of the regions 33a, 33c and 34a, 34c
Can also be corrected. [0039] As described above, according to the present invention, the semiconductor
A concave part having a slope is formed in the body substrate, and a semiconductor is formed in the concave part.
Mount the laser and emit the light from the semiconductor laser on the slope.
And is condensed on the optical recording medium by the condensing means.
So that the output of the semiconductor laser is
Forming a monitoring photodetector for controlling
Formed a photodetector for tracking error signal detection
Therefore, the semiconductor laser, monitor photodetector and
It can be integrated with the photodetector for detecting the king error signal.
Can be downsized. Moreover, tracking error signal detection
The photodetector for slopes has a slope in a direction parallel to the recording track direction.
Formed side by side and record return light by hologram element
Since it was made to diffract in the direction parallel to the rack direction,
The hologram element can be easily manufactured, and the entire optical head is simple.
And it can be inexpensive. In addition, the monitor photodetector
Aligned with the semiconductor laser in a direction almost perpendicular to the track direction
Undesired diffracted light from the hologram element
Incident on the semiconductor laser.
The output power of the laser can be controlled with high accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing a configuration of a first reference example of an optical head developed with the present invention. FIG. 2 is a sectional view of the same. FIG. 3 is a perspective view showing one embodiment of the present invention. FIG. 4 is a perspective view showing a configuration of a second reference example of the optical head developed with the present invention. FIG. 5 is a perspective view showing a configuration of a third reference example. FIG. 6 is a perspective view showing a configuration of a fourth reference example. FIG. 7 is a diagram for explaining a modification of the first reference example. FIG. 8 is a diagram for explaining a conventional technique. DESCRIPTION OF SYMBOLS 11 Holder 12 Laser unit 13 Hologram element 14 Objective lens 15 Silicon substrate 15a V-groove 15b Slope 15c Concavity 16 Semiconductor laser 17-21 Photodetector 22 Parallel plate 22a Half mirror surface 23 Holograms 24a-24c Hologram 25 light Magnetic recording medium 26 Recording track 27 Return light 31-34 Photodetector 35-38 Photodetector 39a-39c Hologram 41a-41d Hologram 51a-51d Photodetector 52a-52d Hologram

Continuation of the front page (56) References JP-A-62-58432 (JP, A) JP-A-64-27289 (JP, A) JP-A-64-35737 (JP, A) JP-A-4-61635 (JP) JP-A-4-155983 (JP, A) JP-A-4-196189 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 7/09 G11B 7/095 G11B 7/125 G11B 7/135

Claims (1)

Claims: 1. A semiconductor substrate, a concave portion having an inclined surface formed in the semiconductor substrate, a semiconductor laser mounted in the concave portion, and light emitted from the semiconductor laser and reflected by the inclined surface. Condensing means for condensing the obtained light on an optical recording medium; a hologram element for diffracting return light from the optical recording medium; and a hologram element formed on the surface of the semiconductor substrate and diffracted by the hologram element. A photodetector for receiving the first-order diffracted light of the return light and detecting a tracking error signal of the condensing means with respect to the optical recording medium; and a controller for controlling an output of the semiconductor laser. A monitor photodetector formed on the semiconductor substrate to receive the emitted light, wherein the photodetector has the slope in a direction parallel to a recording track direction of the optical recording medium. In addition, the photodetector is provided with a plurality of light receiving areas divided by a dividing line parallel to the recording track direction, and the monitor photodetector is provided in a direction substantially orthogonal to the recording track direction. The hologram element is formed alongside the semiconductor laser, and the hologram element is formed in a direction in which a lattice direction is substantially perpendicular to the recording track direction, and the hologram element diffracts the return light in a direction parallel to the recording track direction. An optical head characterized in that: