JPS62185257A - Optical head - Google Patents

Abstract

PURPOSE:To miniaturize an optical head and to attain AF control and AT control more satisfactorily by providing the first and the second optical sensors with light receiving parts in respectively in specific directions and dividing them into two parts. CONSTITUTION:The optical head is composed in the following way; The first optical sensor 28 is provided with light receiving parts 28a-28c for at least the number of light beams along the arranged direction of incident light beams, and respective light receiving parts 28a-28c are divided into two parts in the arranged direction of the incident light beam (y-direction), and the second optical sensor 30 is similarly provided with light receiving parts 30a-30c, and respective light receiving parts 30a-30c are divided into two parts in the orthogonal direction (x-direction) to the arranged direction of the incident light beams. In the light receiving part, images of a light beam spot formed on the surface of an optical card are respectively focused, so that an AT signal can be obtained from the sensor 28 and an AF signal from the sensor 30. Since the optical head can be miniaturized and different sensors can be used for the AF and AT signals, a crosstalk between the AF and AT signals can be prevented, and AF control and AT control can be more accurately attained.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an optical head for an optical information recording/reproducing device.

[Background of the invention]

Conventionally, a disk-shaped medium has been used to record information using light and read out the recorded information.

Various types such as card-shaped, tape-shaped, etc. are known.

Among these, card-shaped optical information recording media (hereinafter referred to as optical cards) are expected to be in great demand as small, lightweight, easy-to-carry, large-capacity media.

In Japanese Patent Application No. 59-276942 and No. 59-276991, the present applicant has already recorded high-density information at high speed while performing accurate auto-tracking (hereinafter referred to as AT) and auto-focusing. In addition, the present invention proposes an optical information recording/reproducing device and an optical card that can read information recorded in this manner at high speed.

FIG. 11 is a schematic plan view showing an example of an optical card similar to that disclosed in the above application.

As shown in the figure, the optical card 101 has clock trunks 1021, 102□, 1023°, . tracking track 103. ．．
103□, . . . are arranged alternately at equal intervals.

And a recording area 1041.104□ for recording information between each track.

104, . . . are provided. That is, optical card 1
01 has a recording area entirely between the clock track and the tracking track.

12 and 13 are diagrams illustrating the configuration of an example of an optical head of an optical information recording/reproducing apparatus that performs recording/reproduction on such an optical card. FIG. 12 is a perspective view, and FIG. 13 is a side view. FIG.

A light beam emitted from a light source 111 such as a semiconductor laser is collimated by a collimator lens 112 and divided into three beams by a diffraction grating 113. These beams are imaged by the objective lens 114 on the information recording surface of the optical card 101 as shown in FIG. 11, and form beam spots S+ and Sz, respectively.

Form S3. Here, the optical card 101 is moved in the direction of arrow R by a driving means (not shown), and is scanned by the beam spot in the direction in which the tracking track and the clock track extend.

The reflected light from the beam spots S+, St, and Sz passes through the objective lens 114 again, is reflected by a mirror 115, and is projected by a condenser lens 116 onto photodetectors 119, 118, and 117 placed on the focal plane. Ru. These photodetectors are arranged side by side in the two directions shown in the figure, as shown in FIG.

Further, the light receiving surfaces of each of the photodetectors 117, 118, and 119 are divided into four sections such as A, B, C, and D.

Next, the operation of recording information on the optical card 101 using the above-mentioned apparatus will be explained with reference to FIG. FIG. 15 shows an enlarged plan view of the information recording surface of the optical card.

First, recording area 104. When recording information on the clock track I, the spots S+, St, and Ss are respectively placed on the clock track I.
Q2+, recording area 104. ,) Rough King Truck 10
3. irradiate. These spots are scanned in the direction of the arrow a by the movement of the optical card 101 as described above.

The reflected light from spot S+ enters the aforementioned photodetector 119, and a clock signal is reproduced. Also, spot S,
The reflected light is incident on the photodetector 117, and a tracking signal is detected. That is, the light receiving surface of the photodetector is y, which corresponds to the length direction of the tracking track, as shown in FIG.
It is divided into A, C and B, D with respect to the direction. Therefore, when the spot S3 deviates from the tracking track 103I, a difference occurs in the intensity of light incident on A, C and B, D, and a tracking signal can be obtained by comparing the signals from these light receiving surfaces. . Based on this tracking signal, tracking means (not shown) (for example,
spot S, by means of moving the objective lens 114 in two directions in FIG.

Sz and Sz are moved together in a direction perpendicular to the scanning direction (b direction) to perform AT. Then, a tracking track 103I is formed in the recording area 104I by the spot S2.
Recording bits 105 are recorded accurately along the line.

Further, during the above recording, the photodetector 117 detects a focusing signal for controlling the spot to be accurately focused on the recording surface of the optical card at the same time as the tracking signal. The principle of this detection will be briefly explained with reference to FIG. 1st
In FIG. 6, the same members as in FIG. 13 are given the same reference numerals, and detailed explanations will be omitted. As shown in the figure, the incident light 120 forming the spot S3 is obliquely incident on the recording surface 121 of the optical card, and the reflected light 122 is reflected when the spot is accurately focused on the recording surface. The light enters the mirror 115 parallel to the incident light 120 and is guided to the detection surface 123. However, the recording surface is 121' with respect to the focal position of the objective lens 114.

When shifted vertically like 121", the reflected light is 122" respectively.
', 122'', the incident light becomes non-parallel, and the irradiation position moves in the y direction on the detection surface 123. Therefore,
Such changes in the light intensity distribution in the y direction are detected on the detection surface 123.
A focusing signal is obtained by detecting the output difference between the light-receiving surfaces A, B and C, D of the photodetector 117 placed on the photodetector 117. According to this focusing signal, the objective lens 114 is moved in the optical axis direction to perform AF.

Next, when recording information in the recording area 1042, by moving the optical system and the optical card 101 relatively in two directions as shown in FIG. 12, spots S+, S2+ are created as shown in FIG. 33 are respectively a tiger knocking track 1032, a recording area 104□, and a clock track 102. Place it so that it scans. Then, the reflected light from the spot S+ is received by the photodetector 119 and AT, A is detected.
While performing F, a clock signal is reproduced by the photodetector 117 from the reflected light of the spot S3, and information is recorded at the spot S2.

That is, by using the two spots St and Ss exclusively for reading the tracking track and the clock track, respectively, and switching the operations as described above, it is possible to record information in all recording areas.

Although the operation for recording information has been described above, the same operation can be performed for reproducing information, and in this case, a reproduction signal is obtained based on the intensity of light incident on the photodetector 118.

Next, the operation of another method of reproducing information recorded on the optical card 1 using the above-mentioned apparatus will be explained with reference to FIG. FIG. 17 shows an enlarged plan view of the information recording surface of the optical card. During reproduction, the intensity of the light beam spot irradiated onto the recorded bits does not need to be so large, so that two columns can be read simultaneously. That is, spot S+,
Sz+Sol is applied to the information track 1251, the tracking track 1031, and the information track 125□, respectively. These spots are scanned in the direction of arrow a in the same manner as in the case of recording described above. Note that in this method, spot irradiation is not performed on the clock track. Suboc)
The reflected light from Sz enters the photodetector 11B, and a tracking signal and a focusing signal are detected in the same manner as in the case of recording above.

In addition, the reflected light from the spots S+ and Ss is detected by the photodetector 11.
9.117, and the entire light-receiving surface A, B of each party detector
A reproduction signal is obtained from the intensity of light incident on , C, and D.

By repeating such operations, information in all N areas of the optical card 101 can be read out at twice the recording speed. In this type of operation, it is not possible to obtain a clock signal from the clock track, but in the case of playback, the clock can be extracted from the signal itself recorded on the information track (so-called self-clocking), so there is no practical problem. .

FIG. 18 is a block diagram showing an example of the configuration of a signal detection circuit for recording and reproducing information as described above in the apparatus shown in FIG. 12. In the figure, 151 is a switch SW
This is a control circuit that controls the opening and closing of I and S Wz, and is 152~156°162~166.169~172
, 175 are addition amplifiers, 157, 158, 167
．． 168°173.174 is a subtraction amplifier, C, -
C.

C6 to C+Z are terminals.

When recording to the recording area 104□, a clock signal CL is obtained at the terminal C2, and a switch SW is connected to the terminal C2 side to send the clock signal CL from the terminal C1 to a processing circuit (not shown).
Supply L. , tracking signal A at terminal C8
T is obtained, the switch SW2 is connected to the terminal C8 side to supply AT from the terminal C6 to the processing circuit, and the terminal C9
A focusing signal AF is obtained at and supplied to a processing circuit. On the other hand, when recording in the recording area 1041, as shown in FIG.
S, , S, respectively illuminate the clock track 102I, the recording area 1041, and the roughing track 1031. In this case, the above-mentioned sw and sw are respectively switched to supply the AT obtained at the terminal C3 to the processing circuit from the terminal CI, the AF obtained at the terminal C4 to the processing circuit, and the AF obtained at the terminal C7. CL is supplied to the processing circuit from terminal C4.

Here, SW+, SW by the control circuit i51.

For example, if an address signal for each track is recorded in advance in the recording area, this address signal is read by the photodetector 118, and the control circuit 151 selects the recording area to be scanned and tracking based on the address signal. The arrangement with the track (which side of the recording area the tracking track is on) is determined.

In the case of the reproduction method in which the reproduction signal is obtained by the reflected light from the spot S2, AT, AP
is obtained, and a reproduced signal RF is obtained from terminal C+Z.

On the other hand, due to the reflected light from spots St and Sz, 2
In the case of a reproduction method that obtains two reproduction signals, the terminal C1°,
At C31, AT and AF are obtained and supplied to the processing circuit. Moreover, the terminal Ct.

The two reproduced signals RF obtained at C7 are supplied to the processing circuit from terminals C, , C, respectively.

[Purpose of the invention]

By the way, the light of the above-mentioned optical information recording and reproducing device...
The throat is attached to the main body of the device so that it can move in two directions,
It is caused to reciprocate by an appropriate driving means. Therefore,
The optical head includes many components such as a light source 111, a collimator lens 112, a diffraction grating 113, an objective lens 114, a mirror 115, a condenser lens 116, and photodetectors 117', 118, 119, etc., and is assembled and adjusted in one piece. It is then assembled into the main body of the device.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an optical head that can be miniaturized and that can perform AF control and AT control more favorably.

[Summary of the invention]

According to the present invention, the above objects include a light source unit capable of generating a plurality of light beams, a pickup lens, a sensor lens, a beam splitter, and two optical sensors, and the two optical sensors are connected to the sensor lens. On the other hand, in the optical head disposed at equivalent positions via the beam subrifter, the first optical sensor is provided with at least as many light receiving sections as the number of light beams along the direction in which the incident light beams are arranged. Each of the light receiving sections is divided into two in the direction in which the incident light beams are arranged, and the second optical sensor is provided with at least as many light receiving sections as the number of light beams along the direction in which the incident light beams are arranged. This is achieved by an optical head characterized in that each light receiving section is divided into two parts in a direction perpendicular to the direction in which the incident light beams are arranged.

〔Example〕

Hereinafter, specific embodiments of the present invention will be described based on the drawings.

FIG. 1 is a schematic exploded perspective view showing the configuration of an embodiment of the optical head according to the present invention, and FIG. This corresponds to a view seen from above in the figure, and FIG. 2 (bl corresponds to a view partially viewed from the side).

First, the optical system of this embodiment will be explained based on FIGS. 2(al) and (b).

2 is a semiconductor laser (hereinafter referred to as LD) as a light source;
The diverging light beam emitted from the LD is condensed by the collimator lens 4 into a parallel light beam.

6 is a light beam shaping prism. Since the light beam emitted from the semiconductor laser 2 and collimated by the collimator lens 4 has a rotationally asymmetric (for example, elliptical) intensity distribution in its cross section, it is passed through the shaping prism 6 so that the light beam remains parallel. Assume that the light beam has an almost rotationally symmetrical cross-sectional intensity distribution.

Note that by combining a plurality of prisms, it is also possible to make the traveling directions of the light beams parallel before and after beam shaping. Further, in this embodiment, the light beam is reduced by beam shaping, but it is also possible to enlarge the light beam by changing the arrangement of the prisms.

8 is a circular aperture, which is used to narrow down the diameter of the light beam to a desired size. That is, the aperture 8 is provided on the optical card 101 in order to set the diameter of the light beam spot to a desired value. The light beam spot diameter is closely related to the alignment characteristics of the LD 2, the focal length and N, A of the collimator lens 4, the variable power ratio of the beam shaping prism 6, and also the focal length and N, A of the pickup lens 14, which will be described later. Therefore, it is preferable to take these into consideration and determine the shape and size of the aperture 8 according to the desired light beam spot diameter and shape.

Incidentally, such an aperture does not necessarily have to be arranged at the position shown in the figure, and may be placed between the collimator lens 4 and the beam shaping prism 6, or between the diffraction grating 10 and the piston, which will be described later.
It may also be placed between the pull-up lens 14 and the pull-up lens 14. Furthermore,
For example, the aperture of the collimator lens 4 can also serve as the aperture 8.

The light beam that has passed through the circular opening 8 enters the diffraction grating 10 and is diffracted by the diffraction grating into three parallel light beams (i.e. 0th order light and ±1
(next order diffraction light). The zero-order light travels in the same X direction as the traveling direction of the light beam incident on the diffraction grating 10.

The light quantity ratio between the 0th-order light and the ±1st-order diffracted light produced by the diffraction grating 10 is determined in consideration of various conditions. That is, the light amount ratio is the medium sensitivity and reflectance of the optical card 101,
Depending on the sensitivity and exposure time of the optical sensors 2B and 30, the relative movement speed between the optical card 101 and the optical head, etc., which will be described later, it is possible to record only with zero-order light during information recording, and the relative It is preferable to determine this so that a sufficiently good reproduced signal can be obtained even if a relatively small amount of +1st-order light is used. As such a light amount ratio, for example, the light amount ratio of -1st order light: 0th order light: +1st order light is 1 = 2:1 to 1:10.
: An example is about 1.

Although either a phase type grating or an amplitude type grating can be used as the diffraction grating 10, a phase type grating is preferable from the point of view of effective use of the amount of light.

In this embodiment, three light beams obtained by diffraction by the diffraction grating 1o are used, but a different number of light beams may be used depending on the recording/reproducing method and the format of the optical card.

Furthermore, depending on the recording/reproducing method and the format of the optical card, a diffraction grating that divides the light into different light quantity ratios than those exemplified above may be used.

The three light beams generated by the diffraction grating 10 are
As shown in FIG. 2(b), it is reflected by the left reflective surface of the roof mirror 12, enters the left half of the objective lens (pickup lens) 14, and is focused by the lens to the optical card 101. Form 3 spots on top.

The reflected light from the irradiation spot on the optical card 101 enters the right half side of the pickup lens 14, is focused by the lens, becomes almost parallel light, and is reflected by the right reflective surface of the roof mirror 12. mirror 16
incident on .

As shown in FIG. 2(a), the light beam reflected by the mirror 16 enters the sensor lens 18. The sensor lens is composed of two groups: a front group 18a with positive power and a rear group 18b with negative power.

The light beam exiting the sensor lens 18 is directed to the mirror 20.22.
．． After being reflected by beam splitter 2
6, the amplitude of the beam is split in two directions by the beam brick, and the beam is incident on a photodetector (photosensor) 28.30.

Note that the mirrors 22 and 24 are arranged orthogonally.

Preferably, beam splitter 26 is a non-polarizing beam splitter. That is, a protective layer can be attached to the recording surface of the optical card 101 to prevent scratches, but some of the materials constituting the protective layer change the polarization characteristics of transmitted light. In this case, the light emitted from the LD 2 is generally linearly polarized light, but the light after passing through the optical card protective layer becomes elliptically polarized light having various ellipticities depending on the location of the optical card. For this reason, if a polarizing beam splitter is used as the beam splitter 26, a phenomenon occurs in which the output level of each sensor differs depending on the location of the optical card, which is not preferable in terms of signal processing. Therefore,
As the beam splitter 26, it is preferable to use a non-polarizing beam splitter with transmittance and reflectance of about 50 to 15% and about 50 to 115%, respectively, for both the p component and the S component in the wavelength range of the LD 2 used. Such a non-polarizing beam splitter may be made of, for example, a glass dielectric (e.g.
in) - can be realized by a structure such as one silver, one dielectric, and one glass. Here, both the dielectric layer and the silver layer can be formed by thin deposition.

The above sensors 28 and 30 are all the above sensor lenses I8.
is placed at the focal point.

FIG. 3 fan, (b) shows the sensors 28 and 30, respectively.
An enlarged view is shown.

As shown in FIG. 3(a), the sensor 28 has three light receiving sections 28a, 28b, and 28c arranged in two directions. Each of these light receiving sections is composed of two light receiving elements A and B divided by a dividing line along the y direction. Images of the three light beam spots formed on the surface of the optical card are formed on these three light receiving sections, respectively. An AT multiplied signal can be obtained from the sensor 28.

As shown in FIG. 3(b), the sensor 30 has three light receiving sections 30a, 30b, and 30c arranged in the X direction. Each of these light receiving sections is composed of two light receiving elements A and B divided by a dividing line along the X direction. and,
Images of the three light beam spots formed on the optical card surface are also formed on these three light receiving sections, respectively. An AF multiplied signal can be obtained from the sensor 30.

Note that when reproducing recorded information, a reproduced information signal can be obtained using either of the sensors 28 and 30.

FIG. 4 is a block diagram showing the configuration of a signal detection circuit for information reproduction, AT, and AF in this embodiment.

In the figure, 32 is S W II"" S W + b
This is a control circuit that controls the opening and closing of 33, 34
．． 35 is an addition amplifier, 36, 37.38, 39°40.41 are subtraction amplifiers, and CZ+ to C35 are terminals.

When recording in the recording area 1041 of the optical card shown in FIG. 15 (W1 time), three light beam spots St
, S2. Si is the light receiving part 28c of the sensor 28,
28b, 28a and the light receiving parts 30c, 30b of the sensor 30
, 30a. At this time, an AF multiplied signal is obtained at the terminal C22, and the switch SW is connected to the terminal CZZ.
from the terminal CWt to the processing circuit (not shown).
F times signal is supplied. A clock signal CL is obtained at the terminal C2B, and the switch SW, 3 is connected to the terminal C2, so that the terminal C2? The CL signal is supplied from the CL signal to a processing circuit (not shown). Switch SW1□ is terminal Czsl Ca
It is in an open state for both terminals b, and therefore terminal C24
There is no output from. An AT multiplied signal is obtained at the terminal CHI, the switch SW, is closed, and the AT multiplied signal is supplied from the terminal C36 to a processing circuit (not shown). switch S
W + s and S W t b are both open, so there is no output from terminals C32 and C24.

At the time of confirmation (corresponding to playback) after the end of W1 (time v1), the only difference from the time of W1 is that the switch SWI□ is connected to the CZS side. Thus, the information signal (RF) obtained at the terminal Cps is supplied from the terminal CZ4 to a processing circuit (not shown).

When recording in the recording area 104□ of the optical card shown in FIG. 15 (at W 2 o'clock) and at the time of confirmation (at VZ time),
and 71 o'clock, respectively, and the light receiving parts 28a and 2 of the sensor 28.
8C and the light receiving sections 30a and 30c of the sensor 30, the roles are switched, and each switch is controlled accordingly.

Further, as shown in FIG. 17 above, two information tracks 125. ．． When reproducing 125□ at the same time (R time), the three light beam spots SI+SZ and S3 are the light receiving portions 28c of the sensor 28, respectively.

28b, 28a and the light receiving section 30C230b of the sensor 30
, 30a. At this time, a reproduction signal (RF) of information of the information track 125t is obtained at the terminal Czt, and a reproduction signal (RF) of the information track 125t is obtained at the terminal C2II.
A reproduction signal (RF) of the information of 1 is obtained, and the switch SW
11. S W I 3 are connected to terminals C2□ and C, respectively.
28 side and terminals Cz 1, C! ? The two RF multiplied signals are supplied from the RF signal to a processing circuit (not shown). AF double signal is obtained at terminal CZ&, switch SW, □
is connected to the terminal ctb side, and the AF multiplied signal is supplied from the terminal C24 to a processing circuit (not shown).

The AT double signal is obtained at the terminal C33, and the switch SW
Is is closed and the AT multiplied signal is supplied from the terminal C3□ to a processing circuit (not shown). Switch SW.

5WI6 are all open, so terminal C: lO
There is no output from +C34.

The above operating conditions are shown in Tables 1 and 2 below.

In Table 1, ◯ and × indicate that the terminal is in a closed state or an open state by a switch, respectively, and Table 2 shows the types of signals obtained at the terminal.

As shown in Table 2 and above, in this embodiment, a two-split type light receiving section is used as the light receiving section constituting the sensor 28.30.

As a result, the amount of hardware can be significantly reduced compared to the case where a four-division type as shown in FIG. 14 is used. That is, for example, FIG. 4 and FIG.
A comparison with FIG. 8 shows that the number of addition amplifiers and subtraction amplifiers in this embodiment is extremely small.

Furthermore, in order to ensure a good S/N ratio, it is desirable to place the processing unit for the output from the sensor as close to the sensor as possible, but in this case, if the processing unit has a large amount of hardware, the optical head Although the dimensions are large, if the amount of hardware is small as in this embodiment described above, it is easy to downsize the optical head.

Further, in this embodiment, the light beam from the sensor lens 18 is split into two by the beam splitter 26, and each light beam is received by the sensors 2B and 30 having the above-mentioned two-split type light receiving section, and each sensor Since the signal and the AF multiplication signal are obtained separately, crosstalk between these two signals can be prevented, thus allowing better control and making it easier and more accurate to adjust the alignment of each sensor when assembling the optical head. can be done.

In this embodiment, the optical card surface and the sensor 28.degree. 30 are arranged at optically conjugate positions with respect to the pickup lens 14 and the sensor lens 18. In the case of such a system, the optical path from the sensor lens 18 to the sensors 28 and 30 tends to be relatively long, but in this embodiment, the optical head can be miniaturized by crossing the optical paths. There is. This point will be explained below.

When using a sensor with a divided light receiving section, a dead zone area forming a dividing line is provided in the light receiving section, but the image of the light beam spot on the optical card formed on the light receiving section is It is preferable that the width be sufficiently large (at least 5 to 10 times the width of the band area) from the viewpoint of effective light detection. The dead zone area of the sensor light receiving section can be easily formed with a width of about 20 μm. Therefore, the light beam spot on the sensor is 150μ in diameter.
It is desirable that it is about m or more. If the focal length of the pickup lens 14 is about 5 mm and the diameter of the light beam spot on the optical card is about 3 to 7 μm, the pickup lens 14 and the sensor lens 18 are arranged in tandem, so the focal length of the sensor lens is Distance 1oo~200
This means that a value of about *+m is preferable. This means that in the case of the optical system arrangement as shown in FIGS. 12 and 13, the distance from the condenser lens (sensor lens) 116 to the photodetectors (sensors) 117, 118, and 119 is 100 to 2.
00n+, which is not advantageous for downsizing the optical head.

Therefore, in the above embodiment, a so-called teletype lens system is used as the sensor lens 18, in which the front group consists of a single lens having positive power and the rear group consists of a single lens having negative power.

Thereby, the lens bank can be shortened compared to the focal length, and the weight can be further reduced.

In addition, in order to obtain practically good imaging performance with such a sensor lens without being affected by differences in surface shape, etc.
The F value of the light flux on the incident side and output side of each car lens is 10 ~
It is desirable that it be larger than about 20. By the way, in order to obtain the aforementioned light beam spot diameter at the sensor position, the diameter of the light beam incident on the sensor lens 18 must be 1 to 2 m.
The focal length (f18.) of the front group 18a is preferably about 20 m or more. This f
The shorter IBm is, the shorter the lens bank can be, but if fI8 is about 20 dragons, and the focal length (f+a) of the entire sensor lens is 150 mm,
If the distance between the front group 18a and the rear group 18b is 0, about IXf19, that is, about 15 mm, then the focal length of the rear group 18b (f
lllb) is approximately -5,771-. Since the refractive index of glass, which is the material of the lens, is about 1.5 to 1.8, even if the rear group 18b is a biconcave lens, its radius of curvature is about 2.9 to 4.5 mm. If the lens diameter is about twice the diameter of the incident light beam (about 41 mm), such a concave lens is not easy to manufacture using normal lens processing techniques and is not suitable for mass production. That is, from the point of view of mass production, it is preferable to use a lens having a radius of curvature that is twice or more the outer diameter. Furthermore,
When using a concave lens as described above, the ratio of the focal length of the front group taa to the focal length of the rear group 18b is F, R, -1f.
+a-/f +sb Since l is large, rear group 18b
Extremely strict precision is required for processing and assembly.

Therefore, in a sensor lens, the value obtained by dividing the lens back by the focal length is defined as the telephoto ratio, and if the influence on parts processing and assembly is taken into account, the telephoto ratio can be calculated using the formula 0.3≦tele ratio≦0. It is preferable to satisfy .7. The lower limit in this equation is based on the above reason, and the upper limit is determined from the viewpoint of shortening the optical path length.

In the above embodiment, the focal length fll+ of the entire sensor lens 18 is 150 fins, and the front group 18a and the rear group 18
Suitable power arrangement of the front group 18a and the rear group 18b when both b are thin single lenses and the distance between the front group and the rear group is set to 0.1×fIll=15−1. and the radius of curvature of each lens (assuming that the radii of curvature on both sides are the same) R,11,l R,,.

Specific examples are shown in Table 3 below. Note that the refractive index of glass, which is a lens constituent material, was 1.5.

Table 3 In this embodiment, the optical path after the sensor lens 18 is bent by mirrors 20, 22, and 24.
Moreover, the beam spreads from the mirror 24.

The optical path leading to the liter 26 intersects with the optical path inside the sensor lens 18. In this way, by crossing the optical paths between the light and the inside of the throat, the space inside the light and the throat can be used effectively, making it possible to make the light and the throat small.

Generally, bending the optical path is a commonly used means to reduce the external dimensions of an optical system, but in this embodiment, further miniaturization is achieved by crossing the optical paths.

Note that the intersection position of the optical paths is not necessarily limited to the above-mentioned position. FIG. 5 is an optical system layout diagram showing a further example of the optical path crossing position, and is a diagram similar to FIG. 2(a). In FIG. 5, the same members as in FIG. 2(a) are given the same reference numerals.

In the example of FIG. 5, the light beam reflected by mirror 16 is reflected by mirror 20, passes through sensor lens 18, is further reflected by mirror 22, and reaches mirror 24. Here, the optical path from the light beam shaping prism to the circular aperture 8 intersects with the optical path from the mirror 22 to the mirror 24, and further from the mirror 16 to the mirror 20,
A circular aperture 8, a diffraction grating 1
0, the roof mirror 12, etc., it is possible to further downsize the optical head.

Next, the mechanism of the above embodiment will be explained based on FIG. In this figure, the same members as in FIG. 2 are given the same reference numerals.

In FIG. 1, numeral 3 is a substrate (hereinafter referred to as LD substrate) on which the LD 2 is fixed, and 5 is a lens barrel of the collimator lens 4. The LD substrate 3 is coupled to the lens barrel 5.

FIG. 6(a) is a longitudinal sectional view of the LD 2, LD substrate 3, collimator lens 4, and lens barrel 5 thereof.

In FIG. 6(a), 5' is an internal lens barrel, and the collimator lens 4 is fixed to the internal lens barrel 5'. The internal lens barrel 5' is made to be able to slide relative to the lens barrel 5 in the optical axis direction of the collimator lens 4, and is fixed to the lens barrel 5 after adjusting the distance between the LD 2 and the collimator lens 4 during assembly. Ru. The LD2 is fixed to the LD board with a screw 1 via a sheet 3' having electrical insulation and excellent heat conductivity, and a collar 1' having electrical insulation properties is provided between the screw 1 and the LD2. is interposed. Furthermore, the LD board 3 is fixed to the lens barrel 5 with screws, etc., but this fixing mechanism is provided with an appropriate clearance in a plane perpendicular to the optical direction of the collimator lens 4, so that when assembling the collimator lens After aligning the optical axes of 4 and LD 2, both can be fixed.

As described later, the lens barrel 5 is fixed to the optical head body frame 11, so in this embodiment as described above, the LD 2
Even if the LD2 takes on a potential other than 0 during operation (which is common), even if you touch the optical head body frame or noise or static electricity occurs on the optical head body frame side, the LD2 has an insulating property. Sheet 3' and insulating collar 1'
Since it is electrically insulated from the LD board 3, there is no adverse effect. Therefore, the LD 2 can always operate stably, and furthermore, it is possible to extend the life of the LD 2.

Furthermore, in this embodiment, since the sheet 3' has excellent heat conductivity, even if the LD 2 is of a high output type, it can be made of a metal with good heat conductivity such as aluminum without installing a special heat sink. Heat can be diffused toward the LD substrate 3 and lens barrel 5 side, and thus the LD 2 can be maintained within a temperature range that allows sufficiently stable operation.

Examples of electrically insulating materials with excellent heat conductivity used for such a sheet 3' include mica, silicone rubber, alumina, boron nitride, silicon nitride, sialon, and sapphire single crystal. are relatively cheap and easily available.

FIG. 6[b] is a longitudinal sectional view showing another example of the LD 2, LD substrate 3, collimator lens 4, and lens barrel 5, and is a view similar to FIG. 6+al.

In this example, an electrically insulating sheet 3' having good heat conductivity is interposed between the LD substrate 3 and the lens barrel 5. Incidentally, the LD substrate 3 and the lens barrel 5 are fixed while maintaining electrical insulation.

Note that by making the LD base tJi 3 or the lens barrel 5 using a material with excellent electrical insulation and heat conductivity such as ceramic, the same effect can be obtained without using the sheet 3' as if using the sheet. You can get the following effect.

Furthermore, in the example shown in FIG. 6(b), if it is possible to maintain the LD2 within the specified temperature range by heat radiation from the surface of the LD substrate 3, the sheet 3' can be used without considering heat conductivity. A simple insulating sheet can also be used. In this way, if the material existing between the electrically insulating material and the LD2 can provide a sufficient heat dissipation effect and can protect the LD2 from noise, an insulating material with good thermal conductivity can be used. You can also use other than that.

In FIG. 1, a lens barrel 5 is fixed to an LD unit substrate 7. As shown in FIG. Further, 9 is a holder that can hold the diffraction grating 10, and this holder is also fixed to the LD unit substrate 7. Furthermore, a light beam shaping prism 6 and a circular aperture 8 are also fixed to the LD unit substrate 7. The above LD unit 1-jJ board 7 and the members fixed to the board are integrally coupled to the optical head body frame 11 as an LD unit.

FIG. 7 is a partially exploded perspective view showing the state in which each member is fixed to the LD unit board 7 and the state in which the LD unit board 7 is fixed to the optical head body frame 11.

As shown in FIG. 7, the LD unit substrate 7 has a substantially L-shaped cross section parallel to the y-z plane, and includes a collimator lens 4, a lens barrel 5, a prism 6, a circular aperture 8, and a diffraction grating holder. 9 is fixed to the inner surface of the LD unit board 7 after adjusting its position. This position adjustment is performed, for example, with reference to the bottom surface 7a parallel to the x-z plane, the side surface 7b parallel to the x-y plane, and the side surface 7C parallel to the y-z plane. That is, the distance between the optical axis of the zero-order light generated by the diffraction grating 10 and the reference planes 7a, 7b and the deviation of the optical axis with respect to the reference plane are within the standard range, and
The distance between and the reference surface 7C is also within the standard range. of course,
Emitted from LD2, collimator lens 4, prism 6
, the optical components are positioned so that the light beam passing through the circular aperture 8 and the diffraction grating 10 has a diameter and parallelism within a standard range.

The LD unit thus adjusted is detachably attached to the optical head body frame 11.

That is, the optical head body frame is formed with a part for attaching the LD unit, and has a surface 11a parallel to the X-2 plane, a surface 11b parallel to the x-y plane, and a surface 11b parallel to the y-z plane. Using surface 11C as a reference surface, place the reference surface of the above LD unit base + Ji7 on each of the two surfaces. a, 7b and 7C
It is positioned by abutting against each other, and is removably attached using means such as screws or clamps (not shown).

In this embodiment, three surfaces are used as positioning references when connecting the LD unit board 7 and the optical head body frame 11, but it is not necessary to use these surfaces as positioning references. It is also possible to replace a part or all of it with a point contact system consisting of a pin and a receiver for the bottle, or a line contact system using a guide means. Furthermore, the number of positioning standards may be less than or more than three, as long as the positioning as described above is achieved sufficiently.

According to this embodiment as described above, the LD unit is assembled and adjusted independently and then attached to the optical head body frame 11 by mechanical means. Among the elements that make up the optical head, the LD has a relatively short lifespan, so it is required to be replaced when the optical head is used.In this case, the LD unit must be replaced with a new LD unit that has been adjusted in the same way. By doing so, sufficient accuracy can be achieved through mere mechanical attachment without adjusting the optical system of the entire optical head. In this way, maintenance management becomes easy, and it becomes possible to improve serviceability and productivity.

In FIG. 1, a roof mirror 12 is fixed to a frame 11. As shown in FIG. Further, 13 is an actuator that has a built-in pickup lens 14 and can drive the lens in the y direction and in two directions, and this actuator is attached to the frame 11.

15 is a lens barrel of the sensor lens 18, and mirrors 16 and 20 are fixed to both ends of the lens barrel.

Further, the lens barrel is fixed to the frame 11.

FIG. 8 is a cross-sectional view of the sensor lens barrel 15.

In FIG. 8, 17a and 17b are retaining rings for the front group 18a and rear group 18b of the sensor lens 18, respectively. Both end surfaces of the lens barrel 15 are formed at predetermined angles with respect to the optical axis of the sensor lens 18, and mirrors 16 and 20 are fixed to each end surface. Also, 19a
, 19b are openings for securing an optical path for the light beam to enter or exit the mirror 16.20. Note that 21 is an aperture for securing an optical path from the mirror 24 to the beam splitter 26, and as shown in the figure, this optical path intersects with the optical axis of the sensor lens 18.

The lens barrel 15 as described above includes the sensor lens 18 and the mirror 1.
6. After positioning, adjusting and fixing the optical head 20, it is assembled into the optical head body frame 11.

According to this embodiment as described above, it is possible to adjust the mirror 16, 20 and the sensor lens 18 in units of the sensor lens barrel 15, and it is possible to improve the positioning accuracy between these optical components. Since this unit can be replaced, maintenance management becomes easy. Furthermore, since both ends of the sensor lens barrel 15 also serve as support members for the mirrors 16 and 20, the number of parts can be reduced, reducing costs and simplifying the mechanism, making the optical head more compact. can also contribute.

Note that the sensor lens barrel 15 and the optical head body frame 1
By making the connecting portion with the optical head 1 similar to the connecting portion between the LD unit substrate 7 and the optical head body frame 11, the same effects as those obtained when attaching the LD unit can be obtained.

In FIG. 1, 23 is a support member for mirrors 22 and 24.

9(al) to (C) are enlarged views of the vicinity of the mirror support member 23. FIG. 9(al) is a partial perspective view;
Figure [b] is a partial plan view, and Figure 9 (C) is Figure 9 (
It is a CC sectional view of a).

The joint surfaces of the mirror support member 23 and the mirrors 22 and 24 are machined so as to form a right angle to each other, and this perpendicularity is formed with sufficient accuracy. The support member 23 has an opening 2 for securing an optical path from the mirror 20 to the mirror 22, an optical path from the mirror 22 to the mirror 24, and an optical path from the mirror 24 to the beam splinter 26.
3a.

23b and 23C are provided. Moreover, the support member 2
A protrusion 23' is provided at the center of the bottom surface of No. 3 along the X direction, and the bottom surface other than the protrusion is processed so as to be on the same plane. And the bottom surface and the mirror 22.24
Sufficient precision has been achieved so that the joint surfaces of the two are orthogonal to each other.

On the other hand, the optical head body frame 11 is formed with an elongated portion 11' along the X direction, and the mirror support member 23 is placed with its bottom protrusion 23' fitted within the elongated portion 11'. There is. In the vicinity of the long length 11', the upper surface of the frame 11 is formed parallel to the xz plane with sufficient precision. Further, 25 is the mirror support member 23
It is a member for fixing, and the upper surface of the fixing member has an
A protrusion is provided along the direction, and the support body 23
Similarly, the projection is arranged in a fitted manner within the elongated portion 11'. The fixing member 25 is provided with two screw holes formed along the y direction. Two through holes in the y direction are formed in the mirror support member 23 at positions corresponding to the two screw holes in the fixing member 25. Reference numeral 27 denotes a screw, which is inserted into the through hole and adapted to the screw hole of the fixing member 25, thereby fixing the mirror support member 23 to the frame 11.

According to this embodiment as described above, the mirror support member 23 can be moved in the X direction with the screw 27 loosened, and thereby the optical system can be adjusted. That is, by moving the mirror support member 23 in the X direction, the optical path length between the sensor lens 18 and the sensor 28°30 can be changed, so that it is possible to change the optical path length between the sensor lens 18 and the sensor 28°30. It is possible to correct deviations from the focused state of the light beam spots formed in the sensors 2B and 30 and deviations in spot spacing.

Furthermore, according to this embodiment, it is possible to obtain an optical path length change that is twice the moving distance of the mirror supporting member 23, and therefore, the moving distance of the mirror supporting member 23 can be relatively small, so that the optical head can be made smaller. It can be realized.

Incidentally, the above optical effects can be obtained not only by combining two mirrors but also by using a right angle prism. However, in order to do this, it is necessary to manufacture a right-angle prism with three optical surfaces precisely formed, and in order to make the optical head smaller and lighter, it is necessary to manufacture a prism with extremely small dimensions. Therefore, the cost of the prism becomes extremely high. Also,
Even when this prism is used, it must be fixed on a table with a fixing means like in the case of this embodiment, and therefore the number of mechanical parts and cost are much different from that of this embodiment. There is no. Furthermore, when a right-angle prism is used, the screws for fixing to the optical head body frame 11 cannot be placed in the position as in this embodiment, and must be placed outside the prism. , which is disadvantageous for miniaturization.

Therefore, it can be seen that the configuration in which the pair of mirrors 22 and 24 are supported by the mirror support member 23 as in the present embodiment is more effective in practice.

As shown in FIG. 1, the beam splitter 26 is fixed to the optical head body frame 11.

Support plates 29 and 31 support the sensors 28 and 30, respectively, and the support plates are respectively attached to the outer surface of the frame 11. Further, reference numeral 52 denotes a through hole formed in the frame 11 along two directions in order to secure an optical path from the beam splitter 26 to the sensor 30. As shown in the figure, the sensor 30 is attached to the support plate 31 so as to face the through hole 52.
is supported by Although not shown, a through hole is formed in the frame 11 along the X direction in order to secure an optical path from the beam splitter 26 to the sensor 28, and the sensor 28 is placed on the support plate 29 so as to face the through hole. is supported by

Further, in the frame 11, a through hole 54 is formed on the opposite side of the through hole 52 with respect to the beam splitter 26 and also along two directions on an extension of the through hole 52.

The through hole 54 is closed with a lid 56 made of a material that does not transmit the laser beam.

In FIG. 1, 58 is the optical head main body frame 1.
1 from above.

FIG. 10 is a partial perspective view for explaining a method of adjusting the mounting positions of the sensors 28 and 30 in this embodiment.

First, with the M56 removed from the through hole 54 of the frame 110, the observation equipment 60 is placed on the two-direction extension of the through hole 54.
Place.

Then, as shown in FIG. 2, the optical card 101 or the reference reflective surface is placed at the reference position, and the light beam is emitted from the LD 2.

As a result, in the optical system as described above, the reflected light beam from the mirror 24 enters the beam splitter 26, a part of which passes through the beam splitter and enters the sensor 28, and the other part of the reflected light beam enters the beam splitter 26. The beam is reflected by the beam splitter and enters the sensor 30. Thus, sensor 28.
Three light beam spots are formed on each of them.

Generally, the light-receiving surfaces of the sensors 28 and 30 reflect and scatter some of the incident light, so the reflected and scattered light from the sensor light-receiving surfaces reaches the beam splinter 26 again. A portion of the light from the sensor 28 is reflected by the beam splitter 26 and enters the observation device 60 through the through hole 54. Similarly, a portion of the light from sensor 30 passes through beam splinter 26 and enters observation instrument 60 through through hole 54 .

Therefore, while observing the relative positional relationship between the three divided light receiving sections and the three light beam spots on each sensor 28 and 30 using a monitor (not shown) connected to the observation device 60, the desired sensor output can be determined. Support plate 2 of each sensor as obtained
The attachment position of the optical head 9.30 to the optical head body frame 11 can be adjusted, which is extremely effective in practice.

After the adjustment is completed, the through hole 54 is covered with a hole 156 to prevent the laser light beam from being emitted to the outside of the optical head. This eliminates any safety issues.

The lid 56 may be placed over the through hole 54 so as to be removable, or it may be fixed so that it cannot be removed once accurate adjustment has been made.

〔Effect of the invention〕

According to the optical head of the present invention as described above, the amount of hardware for sensor output signal processing can be reduced.
It becomes possible to downsize the optical head.

In addition, in the optical head of the present invention, different sensors can be used for AF and AT, so the AF multiplied signal AT
Crosstalk of the doubled signal can be prevented, and thus AF control and AT control can be performed more accurately.

[Brief explanation of drawings]

FIG. 1 is an exploded perspective view of the optical head, and FIG. 2(a),
(bl is the optical system layout diagram. Figure 3 (al), (b) is an enlarged view of the sensor,
The figure is a block diagram of a signal detection circuit. FIG. 5 is a layout diagram of the optical system of the optical head. FIG. 6(b) is a vertical cross-sectional view of the semiconductor laser and the vicinity of the collimator lens. FIG. 7 is an exploded perspective view of the optical head. FIG. 8 is a cross-sectional view of the vicinity of the sensor lens. FIG. 9(a) is a partial perspective view of the vicinity of the orthogonal mirror, FIG. Fig. 1O is a partial perspective view for explaining the method of adjusting the sensor mounting position. Fig. 11 is a plan view of the optical card. Fig. 12 is a perspective view of the optical head, and Fig. 13 is a perspective view of the optical head. Fig. 14 is an enlarged view of the photodetector. Fig. 15 is an enlarged plan view of the optical card during information recording, and Fig. 17 is an enlarged view of the optical card during information reproduction. FIG. 16 is an explanatory diagram of the focusing signal detection principle. FIG. 18 is a block diagram of the signal detection circuit. 2: Semiconductor laser, 3: Semiconductor laser substrate, 3': Insulating sheet, 4: Collimator lens, 5.5': Lens barrel, 6
: Light beam shaping prism, 7: Unit board, 8: Circular aperture, 9: Diffraction grating holder, 10: Diffraction grating, 11: Optical head body frame, 12: Roof mirror, 13: Actuator, 14: Pink amplifier lens, 15 : lens barrel,
16.20, 22, 24: Mirror, 18: Sensor lens, 23: Mirror support member, 25: Fixed member, 26: Beam splitter, 28.30: Sensor, 29.31: Sensor support plate, 52, 54: Penetration hole, 56: lid, 58: lid body, 60: observation equipment, 101: optical card, 102. ~10
23: Closoc trunk, 103. ~1032:) Ranking Trunk, 104. ~1043: Recording area, 12
5+. 125□ = information track, S, ~S3 = light beam spot. Agent Patent Attorney Jo Taira Yamashita 4th figure Zflo 281) 28c
Figure 5 Old figure 8 Figure 6 (a) Figure 6 (b) Figure 11 Figure 13 Figure 14 Figure 15 Figure 16

Claims (1)

[Claims] (1) It has a light source unit capable of generating a plurality of light beams, a pickup lens, a sensor lens, a beam splitter, and two optical sensors, and the two optical sensors are equivalent to the sensor lens through the beam splitter. In the optical head disposed at a position, the first optical sensor is provided with at least as many light receiving sections as there are light beams along the direction in which the incident light beams are arranged, and each of the light receiving sections is arranged in the direction in which the incident light beams are arranged. The second photosensor is divided into two in the alignment direction, and the second optical sensor is provided with at least as many light receiving sections as the number of light beams along the alignment direction of the incident light beams, and each light receiving section is provided along the alignment direction of the incident light beams. An optical head characterized in that it is divided into two parts in a direction perpendicular to .