JPH07101516B2 - Light source - Google Patents

Description

The present invention relates to a light source device used for an optical head or the like of an optical information recording / reproducing apparatus.

[Background of the Invention]

Conventionally, various types of media such as a disk, a card, and a tape have been known as a form of a medium for recording information using light and reading the recorded information. Among these, a card-shaped optical information recording medium (hereinafter referred to as an optical card) is expected to be in great demand as a medium having a large recording capacity that is small and lightweight and convenient to carry.

The applicant has already filed Japanese Patent Application No. 59-276942 and Japanese Patent Application No. 59-27.
In 6991, optical information that can perform high-speed recording of high-density information while performing accurate auto-tracking (hereinafter referred to as AT) and auto-focusing and read the thus recorded information at high speed. A recording / reproducing device and an optical card are proposed.

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 is formed in a continuous linear form with clock tracks 102 ₁ , 102 ₂ , 102 ₃ , ... In which a clock signal is pre-recorded and formed in intermittent broken lines. Tracking tracks 103 ₁ , 103 ₂ , ... Are alternately arranged at equal intervals. Recording areas 104 ₁ , 104 ₂ , 104 ₃ , ... For recording information are provided for each track. That is, the optical card 101 has a recording area in the entire area between the clock track and the tracking track.

12 and 13 are views for explaining the structure of an example of an optical head of an optical information recording / reproducing apparatus for recording / reproducing 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
An image is formed on the information recording surface of the optical card 101 as shown in FIG. 11 by the objective lens 114 to form beam spots S ₁ , S ₂ and S ₃ , respectively. 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 extending direction of the tracking track and the clock track.

The reflected light from the beam spots S ₁ , S ₂ , and S ₃ is again the objective lens 114.
Through the condenser lens 116
Then, the light is projected onto the photodetectors 119, 118 and 117 placed on the focal plane. These photodetectors are arranged side by side in the z direction shown in FIG. 14 as in FIG. Also the photodetector 11
Each of the light-receiving surfaces of 7,118,119 is divided into four like A, B, C, D.

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

First, when information is recorded in the recording area 104 ₁ , the spots S ₁ , S ₂ , S ₃ are recorded in the husband and the clock track 102 ₁ , the recording area 104 ₁ ,
Irradiate the tracking track 103 ₁ . These spots are indicated by the arrow a by the movement of the optical card 101 as described above.
Scanned in the direction. The reflected light from the spot S ₁ enters the above-mentioned photodetector 119, and the clock signal is reproduced. Also, the reflected light from the spot S ₃ enters the photodetector 117,
The tracking signal is detected. That is, the light receiving surface of the photodetector is divided into A, C and B, D in the y direction corresponding to the length direction of the tracking track as shown in FIG. Therefore, if the spot S ₃ deviates from the tracking track 103 ₁ , there will be a difference in the light intensity incident on A, C and B, D, and a tracking signal can be obtained by comparing the signals from these light receiving surfaces. Is. Based on this tracking signal, the spots S ₁ , S ₂ , and S ₃ are perpendicular to the scanning direction (b direction) by a tracking means (not shown) (for example, means for moving the objective lens 114 in the z direction in FIG. 12). It is moved as a unit to AT. Then, in the recording area 104 ₁ , the tracking track 10 is formed by the spot S ₂ .
Recording bits 105 are accurately recorded along 3 ₁ .

Further, in the above recording, the photodetector 117 also detects a focusing signal for controlling the spot so as to be accurately connected to the recording surface of the optical card at the same time as the tracking signal. This detection principle will be briefly described with reference to FIG. 16, the same members as those in FIG. 13 are designated by the same reference numerals, and detailed description thereof will be omitted. The incident light 120 forming the spot S ₃ is obliquely incident on the recording surface 121 of the optical card as shown in the figure, and its reflected light 122 is when the spot is accurately focused on the recording surface. , Mirror 1 which is parallel to the incident light 120
It is incident on 15 and is guided to the detection surface 123. However, when the recording surface is vertically displaced from the focus position of the objective lens 114 like 121 'and 121 ", the reflected light becomes non-parallel to the incident light like 122' and 122", and the detection surface At 123, the irradiation position moves in the y direction. Therefore, a focusing signal can be obtained by detecting such a change in the light intensity distribution in the y direction as an output difference between the light receiving surfaces A, B and C, D of the photodetector 117 placed on the detection surface 123. . In accordance with this focusing signal, the objective lens 114 is moved in the optical axis direction to perform AF.

Then, when recording information in the recording area 104 _2, by a method such as relatively moving the optical system and the optical card 101 in the z direction in Figure 12, the spot as Fig. 15
S ₁ , S ₂ and S ₃ are tracking track 103 ₁ and recording area 10 respectively.
4 ₂ and clock track 102 ₂ are arranged to scan.
Then, while receiving the reflected light from the spot S ₁ by the photodetector 119 and performing AT and AF, the clock signal is reproduced from the reflected light of the spot S ₃ by the photodetector 117, and the information is recorded at the spot S _2. To go.

That is, the two spots S ₁ and S ₃ are exclusively used for reading the tracking track and the clock track, respectively, and information can be recorded in all recording areas by switching the operations as described above.

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

Next, the operation of another method for reproducing the information recorded on the optical card 1 using the above-mentioned device will be described with reference to FIG. FIG. 17 is an enlarged plan view of the information recording surface of the optical card. At the time of reproduction, the intensity of the light beam spot applied to the recording bit does not have to be so large, so that two columns can be read simultaneously. That is, the spots S ₁ , S ₂ , and S ₃ are assigned to the information track 125 ₁ and the tracking track 10 respectively.
Irradiate 3 ₁ and information track 125 ₂ . These spots are scanned in the direction of arrow a as in the case of the above recording. In this method, spot irradiation is not performed on the clock track. Light reflected from spot S ₂ is a photodetector
Upon entering 118, the tracking signal and the focusing signal are detected in the same manner as in the above recording. Further, the reflected light from the spots S ₁ and S ₃ enters the photodetectors 119 and 117,
A reproduction signal can be obtained from the intensity of light incident on all the light-receiving surfaces A, B, C, D of each photodetector.

By repeating such an operation, the information in the entire area of the optical card 101 can be read at a speed twice as high as that at the time of recording. In such an operation, the clock signal cannot be obtained from the clock track, but in the case of reproduction, the clock can be extracted from the signal itself recorded in the information track (so-called self-clock), which is not a practical problem. Absent.

FIG. 18 is a block diagram showing a configuration example of a signal detection circuit for recording and reproducing information as described above in the device of FIG. In the figure, 151 is a control circuit for controlling the opening and closing of the switches SW ₁ and SW ₂ , 152 to 156, 162 to 16
6,169 to 172,175 are summing amplifiers, 157,158,167,168,
173 and 174 are subtraction amplifiers, and C _{1 to} C ₄ and C _{6 to} C ₁₂ are terminals.

At the time of recording to the recording area 104 _2, the clock signal CL is obtained at terminal C _2, supplies the CL to the processing circuit (not shown) from the terminal C ₁ connects the switch SW ₁ to the terminal C ₂ side. Tracking signal AT is obtained at terminal C ₈ and switch SW
₂ is connected to the terminal C ₈ side to supply AT from the terminal C ₆ to the processing circuit, and the focusing signal AF is obtained at the terminal C ₉ and supplied to the processing circuit. On the other hand, the recording area 104 ₁
At the time of recording on, as shown in FIG. 15, the light beam spots S ₁ , S ₂ , and S ₃ irradiate the clock track 102 ₁ , the recording area 104 ₁ , and the tracking track 103 ₁ , respectively. In this case, by switching the SW ₁ and SW ₂ respectively, the AT obtained at the terminal C ₃ is supplied from the terminal C ₁ to the processing circuit, the AF obtained at the terminal C ₄ is supplied to the processing circuit, and The CL obtained at C ₇ is supplied from the terminal C ₆ to the processing circuit.

Here, the switching of SW ₁ and SW ₂ by the control circuit 151 is performed, for example, when an address signal for each track is recorded in advance in the recording area, the photodetector 118 reads this address signal, and the control circuit 151 Based on the address signal,
This is performed by determining the arrangement of the recording area to be scanned and the tracking track (which side of the recording area the tracking track is on).

In the case of a reproducing method for obtaining a reproduced signal by the reflected light from the spot S ₂ , AT and AF are obtained in the same manner as in the above recording,
The reproduction signal RF is obtained from the terminal C ₁₂ .

On the other hand, in the case of the reproducing method in which two reproduced signals are simultaneously obtained by the reflected light from the spots S ₁ and S ₂ , AT and AF are obtained at the terminals C ₁₀ and C ₁₁ , respectively, and are supplied to the processing circuit.
Further, the two reproduction signals RF obtained at the terminals C ₂ and C ₇ are supplied to the processing circuit from the terminals C ₁ and C ₆ , respectively.

[Object of the Invention]

By the way, the optical head of the optical information recording / reproducing apparatus as described above is attached to the apparatus main body so as to be movable in the z direction, and is reciprocally moved by an appropriate driving means. Therefore, the optical head includes a light source 111, a collimator lens 112, a diffraction grating 11
3, the objective lens 114, the mirror 115, the condenser lens 116, and the photodetectors 117, 118, 119, etc. are integrally assembled, adjusted, and assembled into the apparatus main body.

Therefore, it is an object of the present invention to provide a light source device that is used in an optical head or the like and has stable operation and a long life.

[Outline of Invention]

According to the present invention, the above object is to provide a semiconductor laser,
In a light source device having a substrate for fixing the semiconductor laser, a collimator lens provided on the light emitting side of the semiconductor laser, a lens barrel containing the collimator lens, and a frame for mounting the lens barrel, the substrate is A light source device attached to the frame via a lens barrel, wherein the lens barrel is made of an electrically insulating material;
Achieved by

〔Example〕

 Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic exploded perspective view showing the configuration of an embodiment of an optical head according to the present invention, and FIGS. 2 (a) and 2 (b) are optical system layout diagrams thereof. FIG. 2 (a) corresponds to the view seen from above in FIG. 1, and FIG. 2 (b) corresponds to a part of the same seen from the lateral direction.

First, the optical system of this embodiment will be described with reference to FIGS. 2 (a) and 2 (b).

2 is a semiconductor laser (hereinafter referred to as LD) which is a light source,
The divergent light beam emitted from the LD is condensed by the collimator lens 4 to be a parallel light beam. Reference numeral 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,
By passing through the shaping prism 6, a light beam having a cross-sectional intensity distribution that is substantially rotationally symmetric while maintaining the parallel state is obtained.

It is also possible to make the traveling directions of the light beam parallel before and after beam shaping by combining a plurality of prisms. Further, in the present embodiment, the light beam is contracted by beam shaping, but the light beam can be expanded by changing the arrangement of the prisms.

A circular aperture 8 is used to narrow the diameter of the light beam to a desired size. That is, the opening 8 is provided in order to set the light beam spot diameter on the optical card 101 to a desired value. Since the light beam spot diameter has a close relationship with the alignment characteristics of LD2, the focal length and NA of the collimator lens 4, the zoom ratio of the beam shaping prism 6, and the focal length and NA of the pickup lens 14 described later, Taking these into consideration, it is preferable to determine the shape and size of the opening 8 in accordance with 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 drawing, but 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. Further, for example, the aperture of the collimator lens 4 may serve as the opening 8.

The light beam that has passed through the circular aperture 8 enters the diffraction grating 10, is diffracted by the diffraction grating, and travels parallel to the xz plane in three parallel light beams (that is, 0th order light and ± 1st order diffracted light). ) Occurs. The 0th-order light travels in the same x direction as the travel direction of the incident light beam on the diffraction grating 10.

The light quantity ratio of the 0th order light and the ± 1st order diffracted lights produced by the diffraction grating 10 is determined in consideration of various conditions. That is, the ratio of the amount of light depends on the medium sensitivity and reflectance of the optical card 101, the sensitivity and exposure time of the optical sensors 28 and 30 described later, the relative movement speed of the optical card 101 and the optical head, etc. Recording can be performed only by light, and it is preferable to determine so that a sufficiently good reproduction signal can be obtained at the time of reproduction even if ± 1st order light having a relatively smaller light amount than that at the time of recording is used. As such a light quantity ratio, for example, the light quantity ratio of the −1st order light: the 0th order light: the + 1st order light is set to about 1: 2: 1 to 1: 10: 1.

As the diffraction grating 10, either a phase type or an amplitude type can be used, but the phase type is preferable from the viewpoint of effective utilization of the light quantity.

Although three light beams obtained by diffracting by the diffraction grating 10 are used in this embodiment, a different number of light beams may be used depending on the recording / reproducing system and the format of the optical card. Further, depending on the recording / reproducing system and the format of the optical card, a diffraction grating for dividing the light amount ratio different from that exemplified above may be used.

The three light beams generated by the diffraction grating 10 are reflected by the reflecting surface on the left side of the roof mirror 12 as shown in FIG. 2 (b) and left half of the objective lens (pickup lens) 14 It is incident on the 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 is incident on the right half side of the pickup lens 14, is focused by the lens to be substantially parallel light, and is reflected by the reflection surface on the right side of the roof mirror 12. It is incident on the mirror 16.

As shown in FIG. 2A, the light beam reflected by the mirror 16 is incident on the sensor lens 18. The sensor lens is composed of two groups, a front group 18a having a positive power and a rear group 18b having a negative power.

The light beam exiting the sensor lens 18 reaches the beam splitter 26 after being reflected by the mirrors 20, 22, 24,
The beam splitter splits the amplitude in two directions and makes it incident on photodetectors (photosensors) 28 and 30. Mirrors 22 and 24
And are orthogonally arranged.

Beam splitter 26 is preferably a non-polarizing beam splitter. That is, the recording surface of the optical card 101 may be provided with a protective layer for preventing scratches, and some of the materials forming the protective layer change the polarization characteristic of transmitted light. In this case, the light emitted from the LD2 is generally linearly polarized light, but the light after passing through the optical card protective layer is elliptically polarized light having various ellipticities that differ depending on the location of the optical card. Therefore, if a polarization beam splitter is used as the beam splitter 26, the output level from each sensor varies depending on the location of the optical card, which is not preferable for signal processing. Therefore, the beam splitter 26 has a transmittance of 50 ± 15 and a reflectance of 50 ± 15 for both the p component and the s component in the wavelength range of the used LD2.
% And 50-15% non-polarizing beam splitters are preferred. Such a non-polarizing beam splitter can be realized by a structure such as glass-derivative (for example, SiO) -silver-dielectric-glass. here,
Both the dielectric layer and the silver layer can be formed by vapor deposition.

The sensors 28 and 30 are both arranged at the focal position of the sensor lens 18.

3 (a) and 3 (b) show enlarged views of the sensors 28 and 30, respectively.

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

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

When reproducing the recorded information, the reproduced information signal can be obtained by 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 a control circuit for controlling the opening and closing of SW ₁₁ to SW ₁₆ , 33, 34, 35 are summing amplifiers, 36, 37,
38, 39, 40, 41 are subtraction amplifiers, and C _{21 to} C ₃₅ are terminals.

At the time of recording (W ₁ o'clock) in the recording area 104 _{1 of the} optical card shown in FIG. 15, the three light beam spots S ₁ , S ₂ , S ₃ are respectively received by the light receiving portions 28c, 28b, 28b of the sensor 28. Images are formed on the light receiving portions 30c, 30b and 30a of the sensor 28a and the sensor 30. At this time, terminal C ₂₃
At, an AF signal is obtained, the switch SW ₁₁ is connected to the terminal C ₂₃ side, and the AF signal is supplied from the terminal C ₂₁ to a processing circuit (not shown). Clock signal CL is obtained at terminal C _28, switch SW ₁₃ is the CL signal is supplied to the processing circuit (not shown) from the terminal C ₂₇ is connected to the terminal C ₂₈ side. switch
SW ₁₂ is open for both terminals C ₂₅ and C ₂₆ ,
Therefore, there is no output from terminal C ₂₄ . The AT signal is obtained at the terminal C ₃₁ , the switch SW ₁₄ is closed, and the AT signal is supplied from the terminal C ₃₀ to the processing circuit (not shown). Switch S
Both W ₁₅ and SW ₁₆ are open, therefore terminals C ₃₂ and C ₃₄
There is no output from.

At the time of confirmation (corresponding to reproduction) after the end of W ₁ (at V ₁ ), the point that the switch SW ₁₂ is connected to the C ₂₅ side is different from that at the time of W ₁ above. Thus, the information signal (RF) obtained at the terminal C ₂₅ is supplied from the terminal C ₂₄ to the processing circuit (not shown).

At the time of recording to the recording area 104 ₂ of the optical card shown in Fig. 15 (W _2:00), and check the time (at V _2), and a light receiving portion 28a of the W ₁ o'clock and V ₁ o'clock and respectively the sensor 28 28c and the light receiving portions 30a and 30c of the sensor 30 switch their roles, and each switch is controlled in this manner.

When the two information tracks 125 ₁ and 125 ₂ are simultaneously reproduced (R time) as shown in FIG. 17, the three light beam spots S ₁ , S ₂ and S ₃ are respectively detected by the sensor 28. Receiver of
28c, 28b, 28a and the light receiving portions 30c, 30b, 30a of the sensor 30 are imaged. At this time, information track 125 at terminal C ₂₂
The reproduction signal (RF) of the information of ₂ is obtained, and the reproduction signal (RF) of the information of the information track 125 ₁ is further obtained at the terminal C ₂₈ ,
The switches SW ₁₁ and SW ₁₃ are connected to the terminals C ₂₂ and C ₂₈ , respectively, and the two RF signals are supplied from the terminals C ₂₁ and C ₂₇ to a processing circuit (not shown). AF signal is obtained at terminal C _26, switch SW ₁₂ is the AF signal is fed to a processing circuit (not shown) from the terminal C ₂₄ is connected to the terminal C ₂₆ side. A at terminal C ₃₃
The T signal is obtained, the switch SW ₁₅ is closed, and the AT signal is supplied from the terminal C ₃₂ to a processing circuit (not shown). Switch SW
_{Both 14} and SW ₁₆ are open, so there is no output from terminals C ₃₀ and C ₃₄ .

The operation states as described above are shown in Tables 1 and 2 below.
O and X in Table 1 indicate that the terminal is in a closed state and an open state by a switch, respectively, and Table 2 shows the types of signals obtained at the terminal.

As described above, in the present embodiment, the two-division type is used as the light receiving portion constituting the sensors 28 and 30. As a result, the amount of hardware can be significantly reduced as compared with the case of using the 4-division type as shown in FIG. That is, for example, comparing FIGS. 4 and 18 with each other, it can be seen that the number of addition amplifiers and subtraction amplifiers is extremely small in this embodiment.

Furthermore, in order to secure a good S / N, it is desirable to arrange the processing unit for the output from the sensor as close to the sensor as possible, but in this case, if the amount of hardware in the processing unit is large, the optical head Where the size is large, if the amount of hardware is small as in this embodiment, the optical head can be easily downsized.

Further, in the present embodiment, the light beam from the sensor lens 18 is divided into two by the beam splitter 26, and each light beam is received by the sensors 28 and 30 having the above-mentioned two-division type light receiving section. Since the signal and the AF signal are obtained separately, crosstalk between these two signals can be prevented, and thus good control is possible and the alignment adjustment of each sensor when assembling the optical head is easy and accurate. Can be done

In this embodiment, the optical card surface and the sensors 28 and 30 are arranged at positions optically conjugate with 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, 30 tends to be relatively long, but in the present embodiment, the optical head is downsized by crossing the optical paths. There is. Hereinafter, this point will be described.

When a sensor having a divided light receiving section is used, the light receiving section is provided with a dead zone area which forms a dividing line, but the image of the light beam spot on the optical card formed on the light receiving section is the above-mentioned dead zone. A sufficient size (at least about 5 to 10 times or more) with respect to the width of the area is preferable in terms of effective light detection. The dead zone area of the sensor light receiving portion can be easily formed if the width is about 20 μm. Therefore,
The light beam spot on the sensor preferably has a diameter of about 150 μm or more. If the focal length of the pickup lens 14 is about 5 mm and the light beam spot diameter on the optical card is about 3 to 7 μm, the pickup lens
Since the sensor lens 18 and the sensor lens 18 are arranged in tandem, it is preferable that the sensor lens has a focal length of about 100 to 200 mm. This means that the distance from the condenser lens (sensor lens) 116 to the photodetectors (sensors) 117, 118, 119 is about 100 to 200 mm in the case of the optical system arrangement as shown in FIGS. 12 and 13. It is not advantageous for downsizing the optical head.

Therefore, in the above-described embodiment, a so-called teletype lens system is used as the sensor lens 18 in which the front group is a single lens having a positive power and the rear group is a single lens having a negative power. As a result, the lens back can be made shorter than the focal length, and the weight can be further reduced.

Incidentally, in such a sensor lens, in order to obtain a practically good imaging performance without being affected by a difference in surface shape, etc.,
The F-number of the light flux on the incident and exit sides of each single lens is 10 to 20.
It is desirable to be larger than the degree. 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 incident light beam to the sensor lens 18 is about 1 to 2 mm, and therefore the focal length (f _18a ) of the front group 18a is 2 mm.
About 0 mm or more is required. The shorter this f _18a is, the shorter the lens back can be made. However, if f _{18 is set} to about 20 mm, the focal length (f ₁₈ ) of the entire sensor lens is 150 mm.
If the distance between the front lens group 18a and the rear lens group 18b is about 0.1 × f _19, that is, about 15 mm, the focal length of the rear lens group 18b (f _18b )
Is about -5.77 mm. Since the lens material glass has a refractive index of about 1.5 to 1.8, even if the rear lens group 18b is a biconcave lens, its radius of curvature is about 2.9 to 4.6 mm. If the lens diameter is about twice the incident light flux diameter (about 4 mm), such a concave lens is not easy to manufacture by ordinary lens processing technology and is not suitable for mass production. That is, from the viewpoint of mass productivity, a lens having a radius of curvature that is at least twice the outer diameter is preferable. Furthermore, when the concave lens as described above is used, the ratio FR of the focal length of the front group 18a and the focal length of the rear group 18b FR
Since || f _18a / f _18b | is large, extremely strict accuracy is required for processing and assembling the rear group 18b.

Therefore, in the sensor lens, the value obtained by dividing the lens back by the focal length is defined as the tele ratio, and considering the effect on the processing and assembly of parts, the tele ratio satisfies the formula 0.3 ≦ tele ratio ≦ 0.7. Preferably. 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 f of the entire sensor lens 18
₁₈ is 150 mm, the front group 18a and the rear group 18b are both thin single lenses, and the distance between the front group and the rear group is 0.
The front group 18a and the rear group 18b when 1 × f ₁₈ = 15 mm is set.
Table 3 below shows specific examples of the preferable power arrangement of the above and the radius of curvature of each single lens (assuming that the radius of curvature of both surfaces is the same) R _18a and R _18b . The refractive index of glass, which is the lens constituent material, was set to 1.5.

In this embodiment, the optical path after the sensor lens 18 is bent by the mirrors 20, 22, 24, and the optical path from the mirror 24 to the beam splitter 26 intersects the optical path inside the sensor lens 18. . Thus, by intersecting the optical paths in the optical head, the space in the optical head can be effectively used, and the optical head can be downsized.

Generally, in order to reduce the outer size of the optical system, bending the optical path is a frequently used means, but in the present embodiment, further miniaturization is realized by further crossing the optical paths.

The crossing positions of the optical paths are not necessarily limited to the above positions. FIG. 5 is an optical system layout diagram showing a further example of the optical path crossing position, which is similar to FIG. 2 (a). In FIG. 5, the same members as those in FIG. 2 (a) are designated by the same reference numerals. In the example of FIG.
The light beam reflected by the mirror 16 is reflected by the mirror 20, passes through the sensor lens 18, and is further reflected by the mirror 22 to reach the mirror 24. Here, the optical path from the light beam shaping prism to the circular aperture 8 and the optical path from the mirror 22 to the mirror 24 intersect, and further, the mirror 16 to the mirror 20, the sensor lens 18, and the mirrors 22 and 24 are connected. The circular aperture 8 and the diffraction grating are formed by the optical path through the beam splitter 26.
Since the arrangement is made so as to surround 10 and the roof mirror 12 and the like, it is possible to further reduce the size of the optical head.

Next, the mechanism of the above embodiment will be described with reference to FIG. In this drawing, the same members as those in FIG. 2 are designated by the same reference numerals.

In FIG. 1, 3 is a substrate on which LD2 is fixed (hereinafter referred to as LD
(Referred to as a substrate), and 5 is a lens barrel of the collimator lens 4. The LD substrate 3 is connected to the lens barrel 5.

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

In FIG. 6A, reference numeral 5'denotes an internal lens barrel, and the collimator lens 4 is fixed to the internal lens barrel 5 '. The inner lens barrel 5'is made so as to be slidable with respect 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 LD2 and the collimator lens 4 during assembly. It The LD 2 is fixed to the LD substrate with screws 1 through a sheet 3 ′ having electrical insulation and excellent heat conductivity, and a collar 1 ′ having electrical insulation between the screws 1 and LD 2. Is intervened. The LD substrate 3 is fixed to the lens barrel 5 with screws or the like. This fixing mechanism is provided with an appropriate clearance in a plane perpendicular to the optical axis direction of the collimator lens 4, and the collimator is assembled at the time of assembly. After the optical axes of the lens 4 and LD2 are aligned, both can be fixed.

As will be described later, since the lens barrel 5 is fixed to the optical head body frame 11, in the above reference example, when the LD2 takes a potential other than 0 during operation (this is general). Even if the optical head body frame is touched by hand or noise or static electricity is generated on the optical head body frame side, the LD2 is electrically insulated from the LD substrate 3 by the insulating sheet 3'and the insulating collar 1 '. Therefore, it will not be adversely affected. Therefore, the LD2 can always perform stable operation, and the life of the LD2 can be extended.

Further, in the present reference example, since the sheet 3'has excellent heat conductivity, even if the LD2 is a high output type, it is made of a good heat conductive metal such as aluminum without attaching a special heat radiating plate. The heat can be diffused to the LD substrate 3 and the lens barrel 5 side, and thus the LD 2 can be kept within a temperature range where a sufficient stable operation can be performed.

Examples of the electrically insulating material having excellent heat conductivity used for such a sheet 3'include mica, silicon rubber, alumina, boron nitride, silicon nitride, sialon, and sapphire single crystal. Is relatively inexpensive and easily available.

FIG. 6B is a vertical cross-sectional view showing another reference example of the portions of the LD 2, the LD substrate 3, the collimator lens 4, and the lens barrel 5, and is a view similar to FIG. 6A.

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

According to the present invention, the lens barrel 5 is made of a material having excellent electrical insulation such as ceramics, so that the same effect as using the sheet 3'can be obtained without using the sheet 3 '. It is obtained by the configuration.

Further, in the example of FIG. 6 (b), if it is possible to keep LD2 within the specified temperature range by radiating heat from the surface of the LD substrate 3, the sheet 3'does not consider the heat conductivity. A simple insulating sheet can also be used. In this way, if the material existing between the electrically insulating material and LD2 can provide sufficient heat dissipation effect and can protect LD2 from noise, it should be a material other than a material having good thermal conductivity as the insulating material. Can also be used.

In FIG. 1, the lens barrel 5 is fixed to the LD unit substrate 7. Further, 9 is a holder for holding the diffraction grating 10, and the holder is also fixed to the LD unit substrate 7. Further, the light beam shaping prism 6 and the circular aperture 8 are also fixed to the LD unit substrate 7. LD unit substrate 7 above
Also, the member fixed to the substrate is integrally coupled to the optical head body frame 11 as an LD unit.

FIG. 7 is a partially exploded perspective view showing a fixed state of each member to the LD unit substrate 7 and a fixed state of the LD unit substrate 7 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 yz 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 substrate 7 after position adjustment. This position adjustment, for example,
It is performed with reference to a bottom surface 7a parallel to the xz plane, a side surface 7b parallel to the xy plane, and a side surface 7c parallel to the yz plane. That is, the distance between the optical axis of the 0th-order light generated by the diffraction grating 10 and the reference planes 7a and 7b and the deflection of the optical axis with respect to the reference plane are within the reference range, and the diffraction grating 10 and the reference plane 7c are The distance is also within the reference range. Of course, it is emitted from LD2,
Positioning is performed between these optical components so that the light beam that has passed through the collimator lens 4, the prism 6, the circular aperture 8 and the diffraction grating 10 has a diameter and parallelism within a standard range.

The LD unit adjusted in this way is the optical head body frame
It is detachably attached to 11. That is, a portion for mounting the LD unit is formed on the optical head body frame, and a surface 11a parallel to the xz plane, a surface 11b parallel to the xy plane, and a plane parallel to the yz plane are formed. With surface 11c as the reference surface,
The reference plane 7 of the LD unit substrate 7 is attached to each of these surfaces.
Positioning is performed by abutting a, 7b, and 7c, and they are removably attached by means such as a screw or a clamp (not shown).

In the present embodiment, three surfaces are used as the positioning reference when the LD unit substrate 7 and the optical head body frame 11 are coupled, but it is not always necessary to use the surfaces as the positioning reference. It is also possible to replace a part or the whole of the above with, for example, a point-contact type one composed of a pin and a pin receiver or a line-contact type one using a guide means. Further, the number of positioning standards may be less than or more than 3 as long as the above-described positioning is sufficiently performed.

According to this embodiment as described above, the LD unit is independently assembled and adjusted, and then attached to the optical head body frame 11 by mechanical means. Among the elements that make up the optical head
Since the LD has a relatively short life, it is necessary to replace it when using the optical head, but at this time, by replacing the LD unit with a newly adjusted LD unit, Without adjusting the system
Sufficient accuracy can be achieved by merely mechanical attachment. Thus, maintenance management becomes easy, and it becomes possible to improve not only serviceability but also productivity.

In FIG. 1, the roof mirror 12 is fixed to the frame 11. Reference numeral 13 is an actuator that has a pickup lens 14 built therein and can drive the lens in the y direction and the z direction, respectively. The actuator is attached to the frame 11.

Reference numeral 15 is a lens barrel of the sensor lens 18, and mirrors 16 and 20 are fixed to both ends of the lens barrel. Also, the lens barrel is a frame 1
It is fixed at 1.

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

In FIG. 8, 17a and 17b are retaining rings of the front group 18a and the rear group 18b of the sensor lens 18, respectively. Both end surfaces of the lens barrel 15 are formed so as to form a predetermined angle with respect to the optical axis of the sensor lens 18, and mirrors 16 and 20 are fixed to the end surfaces, respectively. Further, 19a and 19b are openings for securing an optical path for entering or emitting a light beam to the mirrors 16 and 20, respectively. Reference numeral 21 is an opening for securing an optical path from the mirror 24 to the beam splitter 26, and the optical path intersects the optical axis of the sensor lens 18 as shown in the drawing.

The lens barrel 15 as described above includes the sensor lens 18 and the mirrors 16, 20.
After positioning and adjusting, fix the optical head frame 11
Be incorporated into.

According to the present embodiment as described above, the mirrors 16 and 20 and the sensor lens 18 can be adjusted in units of the sensor lens barrel 15, and the positioning accuracy between these optical components can be improved. Since this unit can be replaced, maintenance and 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 small, cost can be reduced, and the mechanism can be simplified, and the optical head can be miniaturized. Can also contribute.

The LD lens substrate 15 and the optical head main body frame 11 are connected to each other by the same structure as the LD unit substrate 7 and the optical head main body frame 11 are connected to each other.
The same effect as when mounting the unit is obtained.

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

9A to 9C are enlarged views of the vicinity of the mirror support member 23. 9 (a) is a partial perspective view, FIG. 9 (b) is a partial plan view, and FIG. 9 (c) is a sectional view taken along line CC of FIG. 9 (a).

The joint surfaces of the mirror support member 23 and the mirrors 22 and 24 are processed so as to form a right angle with each other, and this squareness is formed with sufficient accuracy. The support member 23 includes an optical path from the mirror 20 to the mirror 22, and a mirror 22 to the mirror 22.
Optical path to 24 and the beam splitter 26 from the mirror 24
There are openings 23a, 23b, 23c for securing an optical path to the. Further, a protrusion 23 'is provided along the x direction at the center of the bottom surface of the support member 23, and the bottom surfaces other than the protrusion are machined so as to be on the same plane. The precision is sufficiently high so that the bottom surface and the joint surfaces of the mirrors 22 and 24 are orthogonal to each other.

On the other hand, the optical head body frame 11 has a long hole along the x direction.
11 'is formed, and the mirror support member 23 is arranged with its bottom projection 23' fitted in the slot 11 '. In the vicinity of the elongated hole 11 ', the upper surface of the frame 11 is formed with sufficient accuracy in parallel with the xz plane. Further, 25 is a member for fixing the mirror supporting member 23, and a protrusion is provided on the upper surface of the fixing member along the x direction, and like the support 23, the protrusion is provided. It is arranged in the slot 11 'in a fitted state. The fixing member 25 is provided with two screw holes formed along the y direction. Then, the mirror support member 23 is formed with two through holes in the y direction at positions corresponding to the two screw holes of the fixing member 25. Reference numeral 27 denotes a screw, which is inserted into the through hole to be fitted in the screw hole of the fixing member 25, whereby the mirror support member 23 is fixed to the frame 11.

According to the present embodiment as described above, the mirror support member 23 can be moved in the x direction while the screw 27 is loosened, whereby the optical system can be adjusted. That is, since the optical path length between the sensor lens 18 and the sensors 28 and 30 can be changed by moving the mirror support member 23 in the x direction, it is caused by variations in the characteristics of each optical component, processing errors, mounting errors, and the like. It is possible to correct the deviation of the light beam spots formed by the sensors 28 and 30 from the focused state and the deviation of the spot interval. Further, according to this embodiment,
It is possible to obtain a change in the optical path length that is twice the moving distance of the mirror support member 23. Therefore, since the movable distance of the mirror support member may be relatively small, downsizing of the optical head can be realized.

The optical effect as described above can also be obtained by using a right-angle prism outside the combination of two mirrors. However, for this purpose, it is necessary to manufacture a right-angle prism in which three optical surfaces are accurately formed, and in order to reduce the size and weight of the optical head, it is necessary to manufacture a prism having an extremely small size. Therefore, the cost of the prism is extremely high. Further, even when the prism is used, the prism must be fixed on the table having the fixing means as in the case of the present embodiment, and therefore the number of mechanical parts and the cost are the same as in the case of the present embodiment. There is no big difference with. Further, when the right angle prism is used, the screw for fixing to the optical head main body frame 11 cannot be arranged at the position as in the present embodiment,
Since it has to be placed outside the prism, it is disadvantageous for downsizing.

Therefore, it can be seen that the structure in which one set of mirrors 22 and 24 is supported by the mirror supporting 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. Reference numerals 29 and 31 denote support plates for supporting the sensors 28 and 30, respectively, and the support plates are attached to the outer surface of the frame 11, respectively. Reference numeral 52 is a through hole formed in the frame 11 along the z direction in order to secure an optical path from the beam splitter 26 to the sensor 30. As illustrated, the sensor 30 is supported by the support plate 31 so as to face the through hole 52. Although not shown, a through hole is formed in the frame 11 along the x direction to secure an optical path from the beam splitter 26 to the sensor 28.
The sensor 28 is supported by a support plate 29 so as to face the through hole.

Further, in the frame 11, a through hole 54 is formed on the extension of the through hole 52 on the side opposite to the through hole 52 with respect to the beam splitter 26, also along the z direction. The through hole 54 is closed by a lid 56 made of a material that does not transmit the laser light beam.

Further, in FIG. 1, reference numeral 58 denotes a lid body which covers the optical head body frame 11 from above.

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

First, with the lid 56 removed from the through hole 54 of the frame 11, the observation device 60 is arranged on the extension of the through hole 54 in the z direction.

Then, as shown in FIG. 2 (b), the optical card 101 or the reference reflecting surface is arranged at the reference position, and the light beam is emitted from the LD2.

Thereby, in the optical system as described above, the reflected light beam from the mirror 24 is incident on the beam splitter 26, a part of which is transmitted through the beam splitter and incident on the sensor 28,
The other part is reflected by the beam splitter and enters the sensor 30. Thus, three light beam spots are formed on each of the sensors 28 and 30.

In general, however, the light receiving surfaces of the sensors 28 and 30 cause some reflection and scattering of incident light, so that the reflected and scattered light from the sensor light receiving surfaces reaches the beam splitter 26 again. Then, a part 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 part of the light from the sensor 30 is transmitted through the beam splitter 26, passes through the through hole 54, and is used as an observation device.
Incident on 60.

Therefore, a desired sensor output can be obtained while observing the relative positional relationship between the three divided light receiving parts and the three light beam spots on each sensor 28, 30 by a monitor (not shown) connected to the observation device 60. Support plate for each sensor 29,30
It is possible to adjust the attachment position of the optical head to the optical head body frame 11, which is extremely effective in practice.

After the adjustment is completed, the through hole 54 is covered with the lid 56 so that the laser light beam is not emitted to the outside of the optical head. As a result, there will be no problem in terms of safety.

The lid 56 may be detachably attached to the through hole 54, or may be fixed so that it cannot be removed once the accurate adjustment is performed.

〔The invention's effect〕

According to the light source device of the present invention as described above, since the noise current from the frame side can be prevented from reaching the semiconductor laser with a simple configuration, the operation of the semiconductor laser is always stable and the life of the semiconductor laser is long. Also becomes longer.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of the optical head, and FIG.
(B) is a layout view of the optical system. 3 (a) and 3 (b) are enlarged views of the sensor, and FIG. 4 is a block diagram of the signal detection circuit. FIG. 5 is a layout view of the optical system of the optical head. 6 (a) and 6 (b) are vertical cross-sectional views around the semiconductor laser and the collimator lens. FIG. 7 is an exploded perspective view of the optical head. FIG. 8 is a cross-sectional view near the sensor lens. 9 (a) is a partial perspective view near the orthogonal mirror, FIG. 9 (b) is a partial plan view thereof, and FIG. 9 (c) is a cross-sectional view taken along the line CC of FIG. 9 (a). Is. FIG. 10 is a partial perspective view for explaining the sensor attachment position adjusting method. FIG. 11 is a plan view of the optical card. FIG. 12 is a perspective view of the optical head, FIG. 13 is a side sectional view thereof, and FIG. 14 is an enlarged view of the photodetector. FIG. 15 is an enlarged plan view of the optical card when recording information, and FIG. 17 is an enlarged plan view of the optical card when reproducing information. FIG. 16 is an explanatory view 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 substrate, 8: Circular aperture, 9: Diffraction grating holder, 10: Diffraction grating, 11: Optical head frame, 1
2: Roof mirror, 13: Actuator, 14: Pickup 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: Through hole, 56: Lid, 58: Lid, 60: Observing equipment, 101: Optical card, 1
02 _{1-102 3:} clock track, 103 ₁ to 103 _2: tracking tracks, 104 ₁ to 104 _3: recording area, 125 _1, 125 _2: information track, S ₁ to S _3: the light beam spot.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kazuo Minoura 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP-A-60-167130 (JP, A)

Claims (2)

[Claims] 1. A semiconductor laser, a substrate for fixing the semiconductor laser, a collimator lens provided on the light emitting side of the semiconductor laser, a lens barrel containing the collimator lens, and a frame for mounting the lens barrel. In the light source device having, the substrate is attached to the frame via the lens barrel, and the lens barrel is made of an electrically insulating material. 2. The light source device according to claim 1, wherein the lens barrel is made of a material having excellent thermal conductivity.