JPS62185255A - Optical head - Google Patents

Abstract

PURPOSE:To efficiently adjust an optical system and to attain its miniaturization by orthogonally positioning two mirror faces between the sensor lens and the optical sensor, and making the mirrors movable integrally. CONSTITUTION:In an optical head having an optical source 2, a pickup lens 14, a sensor lens 18, at least two mirror faces 22 and 24 and optical sensors 28 and 30 are positioned orthogonally which reflect optical beam continuously between the sensor lenses 18 and the optical sensors 28 and 30, and these two mirror faces 22 and 24 are composed to be able to move integrally along the optical beam incident direction. An optical path from an optical beam shaping prism 6 to a circular opening 8 intersects the optical path from the mirror 22 to the mirror 24. Thus, an optical path length between the sensor lenses 18 and the optical sensors 28 and 30 can be changed in terms of distance efficiency to twice the movable distance of two mirror faces 22 and 24 in a single unit. Consequently, the optical system can be adjusted efficiently, and moreover, the smaller movable range of mirrors of 22 and 24 permits miniaturization of the optical head.

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.

Figure 1) is a schematic plan view showing an example of an optical card similar to the one disclosed in the above application.

As shown in the figure, an optical card 101 has a clock track 102 . . . a clock signal recorded in advance and formed in an intermittent broken line shape. ．． 102□, 102ff.

...and 1. Tracking tracks 103□103□, . . . formed in a continuous linear shape are alternately arranged at equal intervals. A recording area 104 for recording information on each open track can. ．． 104□.

1043, . . . 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 1) 1 such as a semiconductor laser is collimated by a collimator lens 1) 2 and divided into three beams by a diffraction grating 1) 3. These beams are imaged by the objective lens 1)4 on the information recording surface of the optical card 101 as shown in Figure 1), and form beam spots S, St, 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.

Beam spots S,, S2. The reflected light of S3 passes through the objective lens 1) 4 again and is reflected by the mirror 1) 5,
A photodetector 1 placed in the focal plane by a condenser lens 1) 6
) 9, 1) 8.1) Husband is projected onto 7. These photodetectors are arranged side by side in the two directions shown in the figure, as shown in FIG.

Further, the light receiving surface of each of the photodetectors 1) 7, 1) 8, 1) 9 is divided into four parts 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 a clock track t, spots s, , S2+s,
02+, recording area 104. ,) racking truck 10
31. 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 the spot S1 enters the aforementioned photodetector 1) 9, and a clock signal is reproduced. Also, spot S,
The reflected light is incident on the photodetector 1) 7, 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.
For the direction, A, C,! : Divided into B and D. Therefore, when the spot S shifts with respect to the tracking track 1031, 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. be. Based on this tracking signal, spot Sl+S2. S and are moved together in a direction perpendicular to the scanning direction (direction b), and AT is performed. Then, the recording area 104. spot S2
Tracking track 103. Recording bits 105 are recorded accurately along the line.

Further, in the above recording, the photodetector 1) 7 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. 16th
In the figure, 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 Sl 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. , enters the mirror 1) 5 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 1)4.

When shifted vertically like 121#, the reflected light is 122
', 122', the beam becomes non-parallel to the incident light, 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 1) 7 placed in the photodetector 1). According to this focusing signal, the objective lens 1) 4 is moved in the optical axis direction to perform AF.

Next, when recording information in the recording area 104□, by moving the optical system and the optical card 101 relatively in two directions as shown in FIG. S+, St, and S3 are tracking tracks 103. , recording area 104□, and clock track 102□ are arranged so as to be scanned. Then, the reflected light from the spot SI is received by the photodetector 1) 9, and the AT and AF are detected.
While doing this, the photodetector 1 detects the reflected light from the spot S3
)7, the clock signal is reproduced, and information is recorded at spot S2.

That is, by using the two spots S, S3 exclusively for reading the tracking track and the clock track, and switching the operations as described above, it is possible to record information in all recording areas.

The above has explained the operation when recording information, but the same operation can be performed when reproducing information. In this case, a reproduced signal can be obtained based on the intensity of light incident on the photodetector 1) 8. It will be done.

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, spots S,,S
2. S1 respectively to the information track 125. , l-Ruff King Track 103. , the information track 125□ is irradiated. 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. The reflected light from the spot S2 enters the photodetector 1) 8, and a tracking signal and a focusing signal are detected in the same manner as in the case of recording.

In addition, the reflected light from the spots S, S3 is detected by the photodetector 1)
9,1) 7, and the entire light-receiving surface A, B,
A reproduced signal is obtained from the intensity of light incident on C and D.

By repeating such operations, information in the entire area 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-clock), so this is not a practical problem. do not have.

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 the switch SWI
, is a control circuit that controls the opening and closing of SWt, and 1
52~156°162~166.169~172.17
5 is an addition amplifier, 157, 158, 167.16
8°173.174 is a subtraction amplifier, C, ~Cm.

Cb"'C1) is a terminal.

When recording to the recording area 104t, a clock signal CL is obtained at the terminal C2, and a switch SW is connected to the terminal C2 side to transmit the clock signal CL from the terminal C1 to a processing circuit (not shown).
Supply L. Tracking signal AT at terminal Cs
is obtained, a switch SW is connected to the terminal C6 side to supply AT from the terminal C6 to the processing circuit, and a focusing signal AF is obtained at the terminal C1 and supplied to the processing circuit. On the other hand, when recording in the recording area 1041, as shown in FIG.
Sz and S3 are clock trunks 102. , recording area 1041,) racking track 103. It becomes like irradiating. In this case, the above SVl'l, SW
A obtained at terminal C3 by switching Z respectively
T is supplied from terminal C8 to the processing circuit, AF obtained at terminal C4 is supplied to the processing circuit, and CL obtained at terminal C7 is supplied to the processing circuit from terminal C6.

Here, S W+ , S W z by the control circuit 151
For example, if an address signal for each track is recorded in advance in the recording area, this address signal is read out by the photodetector 1) 8, and the control circuit 151 selects the recording area to be scanned based on the address signal. The arrangement of the recording area and the tracking 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, AF
is obtained, and a reproduced signal RF is obtained from the terminal C1□.

On the other hand, due to the reflected light from spots SL and S2, two
In the case of a reproduction method that obtains two reproduction signals, terminal C1゜l
AT and AF are obtained at C1+ and supplied to the processing circuit. Furthermore, two reproduced signals RF obtained at terminals C2 and C1 are supplied to the processing circuit from terminals C+ and Ch, respectively.

[Object of the Invention] Incidentally, the optical head of the optical information recording/reproducing apparatus as described above is attached to the main body of the apparatus so as to be movable in two directions, and is moved back and forth by an appropriate driving means. Therefore, the optical head includes a light source 1) 1, a collimator lens 1) 2, a diffraction grating 1) 3, an objective lens 1) 4, a mirror 1) 5, a condenser lens 1) 6 and a photodetector 1) 7, 1) It includes many component parts such as 8, 1) 9, etc., and is assembled and adjusted as one unit before being incorporated into the main body of the device.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an optical head that can efficiently adjust the optical system and can be downsized.

[Summary of the invention]

According to the present invention, the above object is to provide an optical head that includes a light source, a pickup lens, a sensor lens, at least two mirror surfaces, and an optical sensor, in which a light beam is continuously transmitted between the sensor lens and the optical sensor. This is achieved by an optical head characterized in that two reflected mirror surfaces are arranged so as to be perpendicular to each other, and the two mirror surfaces are movable integrally along the direction of incidence of the light beam.

〔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 FIGS. This corresponds to the view seen from above in FIG. 1, 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 arranged, for example, between the collimator lens 4 and the beam shaping prism 6, or between the diffraction grating 10 and the pickup lens 14, which will be described later. Good too. Further, 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 aperture 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 sensor 28 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 when using the first-order light with a relatively small amount of light. As such a light quantity ratio, for example, the light quantity ratio of -1st order light: 0th order light: 11th 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 10 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 intensity ratios than those exemplified above may be used.

As shown in FIG. 2 (bl), the three light beams generated by the diffraction grating IO are reflected by the left reflective surface of the roof mirror 12 and are reflected by the objective lens (pick-up lens) 14. The light enters the left half side and is focused by the lens to form three spots on the optical card 101.

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 to 6 L/, 8 to 2 by beam splitter
The amplitude is divided in the direction, and the photodetector (photosensor) 28.30
incident on . 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 from 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 whose transmittance and reflectance for both the p component and the S component in the wavelength range of the LD 2 used are approximately 50±15% and 15%, respectively. 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 vapor deposition.

Both of the sensors 28 and 30 are connected to the sensor lens I8.
is placed at the focal point.

The sensors 28 and 30 are shown in FIGS. 3(a) and 3(b), respectively.
(7) Show enlarged view.

As shown in FIG. 3 (al), the sensor 28 has three light receiving sections 28a, 28b, and 28c arranged in two directions. It consists of light-receiving elements A and B. Images of three light beam spots formed on the optical card surface are formed on these three light-receiving sections, respectively.The sensor 28 can obtain an AT multiplied signal. .

As shown in FIG. 3(b), three sensors 3o are arranged in the X direction (7) light receiving 9B30a, 30b,
It has 30 c. Each of these light receiving parts is along the X direction;? It consists of two light-receiving elements A and B separated by the Il line. 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 AP in this embodiment.

In the figure, 32 is a control circuit that controls the opening and closing of SW, ~SW, , 33, 34.35 are addition amplifiers, 36.37, 38.39° 40.41 are subtraction amplifiers, CZ+ to C3% are terminals.

Stcw 4 area 10 of the optical card shown in FIG. 15 above
4, at the time of recording (W+ time), the three light beam spots S+, Sz, and Ss are respectively directed to the light receiving sections 28c, 28b, and 28a of the sensor 28 and the light receiving section 30c of the sensor 30.
, 30b, 30a. At this time, terminal C
22, the AF multiplied signal is obtained, and the switch SW +
+ is connected to the terminal C23 side, and the AF multiplied signal is supplied from the terminal C21 to a processing circuit (not shown). A clock signal CL is obtained at a terminal CZa, a switch SW,1 is connected to the terminal C2Il side, and the CL multiplied signal is supplied from a terminal C27 to a processing circuit (not shown). The switch SWI□ is open to both terminals C2 and C26,
Therefore, there is no output from terminal C24. An AT multiplied signal is obtained at the terminal C31, the switches SW, . . . are closed, and the AT multiplied signal is supplied from the terminal C3° to a processing circuit (not shown). switch sw, 2. sw and 6 are both open, so there is no output from terminal C3Z+C34.

At the time of confirmation (corresponding to regeneration) after the end of W1 (at V r time), the only difference is that the switch SW1□ is connected to the C25 side compared to the time of W1. Thus, the information signal (RF) obtained at the terminal CZS is supplied from the terminal Cta to a processing circuit (not shown).

When recording in the recording area 104t of the optical card shown in FIG.
At 1 o'clock and 71 o'clock, the roles of the light receiving sections 28a and 28c of the sensor 28 and the light receiving sections 30a and 30c of the sensor 30 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), three light beam spots Sl+S2. S, respectively, represent the light receiving section 28c of the sensor 28.

28b, 28a and the light receiving section 30c of the sensor 30.

The images are formed on 30b and 30a. At this time, terminal C2
At □, the information reproduction signal (R
F) is obtained, and information track 1 is also obtained at terminal CZa.
25. A reproduction signal (RF) of the information is obtained, and the switch 5
WII and 5WI3 are connected to the terminal C2□l CAB side, respectively, and the two RF signals are supplied from the terminals cwt and czt to a processing circuit (not shown). An AF multiplied signal is obtained at the terminal CZt+, and the switch SW, 2 is connected to the terminal C
Z6 side, and the AF multiplied signal is supplied from terminal CZ4 to a processing circuit (not shown).

The AT double signal is obtained at the terminal C31, and the switch SW+
s is closed and the corresponding A is passed from terminal C3□ to a processing circuit (not shown).
T times signal is supplied. Switch SW+a.

Both SW+b are open, so terminal C3°.

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, it is desirable to place the processing section for the output from the sensor as close to the sensor as possible; however, in this case, if the processing section has a large amount of hardware, the optical Although the size of the head becomes large, if the amount of hardware is small as in this embodiment described above, it becomes 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 having 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 formed in the dead zone. It is preferable that the size is sufficiently large (at least 5 to 10 times larger than the width of the 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 51 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 sensor lens as focal path #100~2
A diameter of about 0.00 mm is preferable. In other words, in the case of the optical system arrangement as shown in Fig. 12 and Fig. 13, from the condenser lens (sensor lens) 1) 6 to the photodetector (sensor) 1) 7, 1) 8, 1) 9. The distance is 100
This means that it is about 200 dragons, 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 back 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 above-mentioned light beam spot diameter at the sensor position, it is preferable that the diameter of the light beam incident on the sensor lens 18 is about 1 to 21, and therefore the focal length of the front group 18a (
flo-) is required to be approximately 20+m+* or more. The shorter this fl[1m is, the shorter the lens hack can be, but if flll is about 2 (1+m), the focal length (r+a) of the entire sensor lens will be 150 ***
In this case, the distance between the front group 18a and the rear group 18b is 0, I
If it is about Xf+q, that is, about 15 degrees, the focal length ([+sb) of the rear group L8b will be about -5.77fi. Since the refractive index of glass, which is the material of the lens, is about 5 to 1.8, even if the rear group 18b is a biconcave lens, its radius of curvature is about 2.9 to 4.6 mm. If the lens diameter is approximately twice the diameter of the incident light beam (approximately 4 1), 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 ratios F and R of the focal length of the front group 18a and the focal length of the rear group 18b are
,=l f +a-/f I8b Since l is large, extremely strict precision is required for processing and assembling the rear group 18b.

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-mentioned reason, and the upper limit is determined from the viewpoint of shortening the optical path length.

In the above embodiment, the focal length r+s of the entire sensor lens 18 is 150 yen, and the front group 18a and the rear group tsb
Assume that both are thin single lenses, and the distance between the front group and the rear group is 0. Specific example of the preferred power arrangement of the front group 18a and rear group 18b and the radius of curvature of each vehicle lens (assuming that the radius of curvature on both sides is the same) R+a□ R1) 1b when setting IXf+s=151m are shown in Table 3 below. Note that the refractive index of the glass that is the lens constituent material is 1.
I gave it a 5.

Table 3 In this embodiment, the optical path after the sensor lens 18 is bent by mirrors 20, 22, and 24.
Moreover, the optical path from the mirror 24 to the beam splitter 26 intersects with the optical path inside the sensor lens 18. Thus, by crossing the optical paths within the optical head, the space within the optical head can be used effectively, making it possible to downsize the optical head.

In order to reduce the external dimensions of an optical system, bending the optical path is often used, but in this example, 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 (al). In FIG. 5, the same members as in FIG. 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 (al is a longitudinal sectional view of the LD 2, LD substrate 3, collimator lens 4, and lens barrel 5 thereof).

In FIG. 6 (al), 5' is an internal lens barrel, and the collimator lens 4 is fixed to the internal lens barrel 5'. After adjusting the distance between the LD2 and the collimator lens 4 during assembly, the LD2 is fixed to the lens barrel 5.The LD2 is a sheet having electrical insulation properties and excellent heat conductivity. 3' to the LD board with screws 1, and an electrically insulating collar 1' is interposed between the screws 1 and LD2. Although it is fixed to the lens barrel 5, this fixing mechanism is provided with an appropriate clearance in a plane perpendicular to the optical direction of the collimator lens 4, and the optical axis alignment between the collimator lens 4 and the LD 2 is made during assembly. Both can be fixed after this is done.

As described later, the lens barrel 5 is fixed to the optical head body frame 1), so in this embodiment as described above, the LD 2
Even if the LD2 takes a potential other than O during operation (which is common), the LD2 is insulating even if you touch the optical head main body frame or noise or static electricity occurs on the optical head main frame side. 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 (bl is a longitudinal cross-sectional view showing another example of the LD 2, LD substrate 3, collimator lens 4, and lens barrel 5, and is the same view as FIG. 6(a)).

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 substrate 3 or the lens barrel 5 using a material with excellent electrical insulation and heat conductivity such as ceramic, the same effect can be achieved even without using the sheet 3'. Effects can be obtained.

Furthermore, if it is possible to maintain the LD2 within the specified temperature range by heat dissipation from the surface of the LD substrate 3 in the example shown in FIG. A sheet can also be used.In this way, if the material existing between the electrically insulating material and the LD2 has a sufficient heat dissipation effect and can protect the LD2 from noise, a sheet can be used as the insulating material. Materials other than those with good conductivity can also be used.

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, the light beam shaping prism 6 and the circular aperture 8 are also
It is fixed to the D unit board 7. The above LD unit board 7 and the members fixed to the board are integrally L
It is connected to the optical head body frame 1) as a D 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 1].

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-7 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 orientation 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 thus adjusted L+'), -'l- knits are removably attached to the optical head body frame 1).

That is, the optical head body frame is formed with a part for attaching the LD unit, and its surfaces 1)a parallel to the x-2 plane, 1)b parallel to the x-3' plane, and y- The reference planes 7a, 7b, and 7C of the LD unit board 7 are attached to the plane 1)c parallel to the z plane as a reference plane, respectively.
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 the LD unit board 7 and the optical head body frame 1) are connected, but it is not necessary to use the surfaces as positioning references. Part or all of these may be replaced by, for example, a point contact system consisting of a pin and a receiver for the pin, 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 1) 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 1). Further, 13 is an actuator which 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 1).

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 a frame 1).

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 adjusting and fixing the position of 20, it is assembled into the optical head body frame 1).

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
) has the same structure as the connecting portion between the LD unit board 7 and the optical head body frame 1), the same effect as when attaching the LD unit can be obtained.

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

9(a) to (C1) are enlarged views of the vicinity of the mirror support member 23. FIG. 9(a) is a partial perspective view;
Figure (b) is a partial plan view, and Figure 9 (C1 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 be perpendicular to each other, and these surface angles are 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 splitter 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 1) is formed with an elongated hole 1)' along the X direction, and the mirror support member 23 has a bottom protrusion 23' fitted into the elongated hole 1)'. It is located in In the vicinity of the length 1)', the upper surface of the frame 1) is formed parallel to the xz plane with sufficient accuracy. 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 protrusion is arranged in a fitted manner within the elongate 1)'. 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 1).

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 28 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 using a right-angle prism, the screw for fixing it to the optical head body frame 1) 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 splinter 26 is fixed to the optical head body frame 1).

Support plates 29 and 31 support the sensors 28 and 30, respectively, and the support plates are each attached to the outer surface of the frame 1). Further, reference numeral 52 designates through holes drilled in two directions in the frame 1) to ensure 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 1) 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 a support plate facing the through hole. It is supported by 29 people.

Further, in the frame 1), 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 material 156 that does not transmit the laser beam.

Further, in FIG. 1, reference numeral 58 indicates the optical head body frame 1.
) from above.

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

First, with the cover 56 removed from the through hole 54 of the frame 1), the observation equipment 60 is placed on the two-direction extension of the through hole 54.
Place.

Then, as shown in FIG. 2(b), 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 2B,
Three light beam spots are formed on 30, respectively.

Generally, the light-receiving surfaces of the sensors 28 and 30 reflect and scatter some of the incident light, so that 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 is transmitted through beam splitter 26 and viewed through through hole 54? 1LII device 60.

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
9. Attaching to the optical head body frame 1) of 30・1. ;
The position 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.

Note that the lid 5G may be placed over the through hole 54 so as to be removable, or 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 optical path length between the sensor lens and the optical sensor can be efficiently changed by a distance twice the integral movement distance of the two mirror surfaces.
The optical system can be adjusted very effectively, and since the movable range of the mirror is small, the optical head can be made smaller.

[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 3fa), (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. 6(a) and 6(b) are longitudinal cross-sectional views 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. 9(bl is a partial plan view thereof, and FIG. 9(C) is a c-cl! JT plane view of FIG. Fig. 10 is a partial perspective view for explaining the sensor mounting position adjustment method. Fig. 1) is a plan view of the optical card. Fig. 12 is a perspective view of the optical head; 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 plan 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': Insulation gender 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, 1): Optical head body frame, 12: Roof mirror, 13: Actuator, 14: Pick-up lens, 15 : lens barrel,
16.20, 22.24: Mirror, 18: Sensor lens, 23: Mirror support member, 25: Fixing member, 26: Beam splitter, 2B, 30: Sensor, 29.31: Sensor support plate, 52.54: Through hole, 56: lid, 58: lid body, 60: observation device, 101: optical card, 102. ~10
2:+: Clock Trasok, 1031-103□ Nidorakku Track, 104. ~104z: recording area,
125. . 1252: Information track, S, -53: Light beam spot. Agent Patent Attorney Jo Taira Yamashita Figure 4 28a 28b 28c Figure 5 Old Figure 8 Figure 9 (a) y Figure 15 Figure 16

Claims (1)

[Claims] (1) In an optical head that includes a light source, a pickup lens, a sensor lens, at least two mirror surfaces, and an optical sensor, the two mirror surfaces on which the light beam is continuously reflected between the sensor lens and the optical sensor are mutually An optical head, characterized in that the two mirror surfaces are arranged orthogonally to each other and are movable integrally along a light beam incident direction.