JPH0294035A - Optical head - Google Patents

Abstract

PURPOSE:To stabilize a semiconductor laser light emitting quantity without increasing the weight and complicating the constitution by using a non-polarizing beam splitter to provide a reflecting surface. CONSTITUTION:After a light flux from a semiconductor laser 108 goes to a parallel light by a collimator lens 109 and the flux receives the amplitude division with a non-polarizing splitter 11, a transmitted light flux is diaphragmed as an optical spot onto an optical card 101 by an objective lens 111. After the light flux reflected by the card 101 is reflected, the flux arrives at the light receiving part of a sensor 28. The light flux reflected by other splitter 11 is reflected by a reflecting surface 17 of the splitter 11 again, passes through the splitter 11 again and arrives at the light receiving part of the sensor 28. The reflecting surface 17 is inclined, for that reason, the reflected light flux proceeds by the angle different from the light flux reflected by the card 101, and consequently, in the light receiving part of the sensor 28, converged to the positive different from the reflecting light from the card 101. Based on the output of the sensor 28, the light emitting quantity of the laser 108 is controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical head used in an optical information recording/reproducing device, and particularly to an optical head using a semiconductor laser as a light source.

[Prior Art] Various types of media, such as optical discs, optical cards, and optical dezos, have been known as media for recording and reproducing information using light. Each of these has its own characteristics.
Optical cards are used differently depending on purpose, purpose, etc., and it is thought that optical cards will be used more widely in the future, taking advantage of their characteristics such as ease of manufacture, portability, and ease of access.

FIG. 10 is a schematic block diagram showing an example of an optical information recording/reproducing apparatus configured for a card-shaped recording medium.

In the figure, 101 is an optical card on which information is to be recorded, and 103
is the optical head (the part surrounded by the dotted line in Fig. 10),
104 is a light beam, 105 is a shuttle on which the optical card 101 is placed, +08 is a semiconductor laser light source, and +09 is a collimator lens. +10 is a polarizing beam splitter,
+30 is treated as a 1/4 wavelength, and the combination of these two members allows light traveling from the top to the bottom of the diagram to pass through, but light traveling from the bottom toward 10 is bent in the right angle direction. Reference numeral 111 denotes an objective lens which serves to condense parallel light onto an optical card ] -L.

112 is an optical sensor, 113 is a preamplifier, 114 (or auto-focusing servo), 115 (or auto-tracking servo), 116 is a decoder, 117 is an interface, 118 is a combination coater, +19 is an encoder,
120 is a laser driver, and 12] is a stepping motor that functions to move the optical head 103 in a direction perpendicular to the paper surface.

122.123 are the pulleys 122.12 and 123 respectively.
A belt 124 is attached to the belt 3. The belt 12
4 has a shuttle +05 on which the optical card +01 is placed and fixed. Pulley 122 is attached to the shaft of motor 126 and
The rotation of the optical card 101 causes the optical card 101 to reciprocate in the six directions of arrows in the figure.

Next, the operation of the apparatus shown in FIG. 10 will be explained using the case of information reproduction as an example.

In FIG. 10, the light beam oscillated from the semiconductor laser 108 is turned into parallel light by the collimator lens 109.
The light passes through the polarizing beam splitter +10 and the quarter-wave plate 130 and is further focused by the objective lens 111 to form a minute spot on the optical card 101. optical card 1
The reflected light from 01 is modulated depending on whether or not there is an information bit in the area irradiated by the minute spot, and this modulated light is turned into parallel light by objective lens III again.
The light is incident on the optical sensor 112 by the polarizing beam splitter +10. The optical sensor 112 detects a change in the amount of modulated light, converts it into an electrical signal, and sends it to the preamplifier 113. A signal is sent from the preamplifier 113 to the autofocusing servo 114, and in response to a signal from the autofocusing servo 114, an actuator (not shown) moves the objective lens 111 in the direction B, thereby creating a light beam]04
The objective lens 1 is focused on the optical card 101.
11 and the optical card 101.

Another preamp! The signal from 13 is also sent to an auto-tracking servo 115, and the signal from the odo-tracking servo 115 causes an actuator (not shown) to move the objective lens I11 in a direction perpendicular to the plane of the paper, so that the light beam 104 is positioned at a predetermined position. control to focus on.

Note that during the initial operation of the device, the interface 117
A servo pull-in command is sent from the autofocusing servo 114 to the autotracking servo 115.

Several specific methods have been proposed for the auto-focusing servo 114 and the auto-tracking servo 115. For example, the light beam 104 is divided into a plurality of parts using a grating, etc. An example has been proposed in which a tracking track is preformatted, information is reproduced using at least one of a plurality of light beams, and signals for autofocus and tracking are taken out using other beams. Further, the signal from the preamplifier 113 is sent to the 5 decoder + 16 and subjected to necessary electrical processing, and then sent to the interface 117. An information message is sent from the interface 117 to the computer +18. Also, from the interface 117,
After the signal is sent to the encoder 119 and modulated as necessary, it is sent to the semiconductor laser 1 via the laser driver 120.
Controls the oscillation of 08.

Furthermore, signals are sent from the interface 117 to the stepping motor 121 and the motor servo +27, which control the rotation of the position control motor 126 in the direction perpendicular to the plane of the paper of the optical head 103, respectively.

[Problems to be Solved by the Invention] In the optical head 103 explained using FIG. 10, stabilization of the output of the semiconductor laser IO8 is an important technical issue in order to prevent erroneous recording or erroneous reproduction of information. One example is technology. Various proposals have been made in the past to address this technical problem, such as the Japanese Patent Publication No. 1983- ] 04
An example of this is described in Publication No. 81. In this publication, a photoelectric conversion element collects laser light emitted from the opposite side of the reproducing laser beam of a semiconductor laser, compares the output voltage from the photoelectric conversion element with a reference voltage, and calculates the comparison result. A technique for controlling the output of a semiconductor laser based on this has been disclosed.

However, when this technique is applied to the optical head shown in FIG. 1O, it may have the following drawbacks. 1st
FIG. 1 shows a schematic diagram of an optical card 101. As shown in FIG. The optical card 101 is constructed by adhering a transparent protective layer 13+ and a support base 132, and an information recording layer 133 is provided on the adhesive surface. Light enters from the transparent protective layer 131 side. In order to take advantage of the features of the optical card 101 such as portability and flexibility, a transparent protective layer 131. The support base 132 is often made of polymer resin, and in particular, polycarbonate is widely used due to its manufacturing convenience. However, polycarbonate is known to have the drawback of producing birefringence during manufacturing, transportation, and storage. When recording/reproducing information on the optical card 101 having such birefringence using the optical head 103 shown in FIG. 112, and a portion of the light beam returns to the semiconductor laser 108. At this time, if the optical head stabilizes the output of the semiconductor laser 108 using the technique described in Japanese Patent Publication No. 54-1048 as described above, the returned light will be transmitted to the photoelectric conversion element inside the semiconductor laser 108. As a result, the control circuit operates to reduce the output of the semiconductor laser 108. For this reason, for example, during recording, a sufficient amount of light does not reach the optical card IOI, resulting in poor recording.

A further conventional example of stabilizing the output of the semiconductor laser 108 is the technique described in Japanese Patent Publication No. 18354/1983. According to the embodiment in the same publication, a prism is provided in the optical path from the semiconductor laser to the recording medium to direct the reflected light flux from the recording medium to the information FJi raw light photodetector, and the prism A portion of the light beam directed from the laser toward the recording medium is reflected and guided to one of the two-split sensors, and the amount of light emitted by the semiconductor laser is controlled using the difference signal between the output of that sensor and the output of the other sensor. According to this method, since the photodetector for controlling the amount of light emitted by the semiconductor laser is located outside the semiconductor laser, the above-mentioned problem caused by light returning from the optical card to the semiconductor laser is solved. .

However, the conventional example described above has the following drawbacks.

That is, in the conventional example described above, since it is necessary to provide the photodetector outside the prism, it is necessary to provide a holding portion for the photodetector in the optical head housing I+, which increases the weight of the head. Historically, when attempting to receive a large-diameter beam such as a collimated beam, a photodetector having a light-receiving portion of human blood is required, which is disadvantageous in terms of responsiveness and cost of the detector. When using a photodetector with a small light-receiving area, a lens for condensing light is inevitably required, which is also disadvantageous in terms of head weight N1 and cost.

Further, as another technique for stabilizing the output of the semiconductor laser 108, there is a technique disclosed in Japanese Patent Publication No. 8495/1983. According to the example in the publication, out of the divergent light flux from the semiconductor laser, the light flux at a position that is not focused by the objective lens is captured by a detector, and the output of the semiconductor laser is stabilized by the output of this detector. Therefore, the problems of the above two embodiments are solved. However, with the above means, the amount of light reaching the detector is small, the S/N ratio of the output of the detector is low, and there are problems in accurately stabilizing the semiconductor laser. On the other hand, in order for the photodetector to receive a sufficient amount of light, it is necessary to increase the output of the semiconductor laser, which is not preferable.

[Means for Solving the Problems] In view of the problems of the prior art described above, an object of the present invention is to increase the amount of light emitted by a semiconductor laser without increasing the weight or complicating the configuration compared to a conventional optical head. An object of the present invention is to provide an optical head that can achieve stabilization.

The above objectives include the semiconductor laser that is the light source, the collimator lens, the non-polarizing beam splitter, the objective lens, and the first
a photodetector, a condensing lens for condensing light on the first photodetector, and a second photodetector, and the light from the semiconductor laser is collimated by the collimator lens. The output light flux is irradiated onto an optical information recording medium, and the reflected light is amplitude-divided by the non-polarizing beam splitter and guided to the first photodetector via the condenser lens to record and/or reproduce information. The optical head includes a reflecting surface (reflection mirror, beam splitter, the second photodetector is provided at a position where the light beam reflected by the reflection surface is focused by the condenser lens, and the output of the photodetector is This is achieved by the optical head A of the present invention, which is characterized in that the output of the semiconductor laser is controlled by using the semiconductor laser.

The above purpose also includes a semiconductor laser as a light source, a collimator lens, a non-polarizing beam splitter, an objective lens, a first
at least a photodetector, the first photodetector, and the second photodetector, and irradiates an optical information recording medium with a beam emitted from a semiconductor laser that is collimated by the collimator lens, An optical head for recording and/or reproducing information by splitting the amplitude of the reflected light by the non-polarizing beam splitter and guiding it to the first photodetector, wherein the 0?1 non-polarizing beam splitter is the non-polarizing beam splitter. It has a reflective surface (including a reflective mirror and a reflective surface 17 provided on a beam splitter) for reflecting a light beam that is not directed toward the optical information recording medium, and the light beam reflected by the reflective surface is reflected by the collimator lens. the second photodetector is provided at a position where the light is focused;
This can also be achieved by the optical head (3) of the present invention, which is characterized in that the output of the semiconductor laser is controlled using the output of the photodetector.

[Function] 1-Distribution According to the optical head A and the optical head 13 according to the present invention, the condenser lens for condensing light onto the first photodetector, the remeter lens, together with their original functions. By using it also as a condensing lens that condenses light onto a second photodetector for controlling the output of the semiconductor laser, there is no need to newly provide a condensing lens for this purpose.

Further, among the light beams whose amplitude has been split by the non-polarizing beam splitter, the light beams which are not directed toward the optical information recording medium are reflected by a planar reflecting surface tilted with respect to the principal ray thereof, respectively. By focusing the light onto a photodetector at a different position from the original position using a condenser lens and a collimator lens, it can be easily separated into information signal light and light directed towards the laser, respectively. be able to.

In addition, compared to conventional optical heads, the present invention basically requires only the installation of a reflective surface, and (1) position adjustment of the optical system is easy, and detection can be performed with a sufficient amount of light.
A stable signal with a good S/N ratio can be obtained.

[Examples] Hereinafter, the optical head according to the present invention will be described in detail based on specific examples.

FIG. 1 is a diagram illustrating a first embodiment of the optical head Δ according to the present invention, and the figure is a schematic block diagram of an optical head that uses an astigmatism method for focus control and a push-pull method for tracking control. .

In the figure, 7 is a CPU that controls the entire system;
is an interface, 2 is an encoder, 3 is a laser control unit that controls the laser driver 4 using the signal from the comparator 6 and the signal from the encoder 2, 5 is an amplifier that amplifies the output from the sensor 28, and 6 is a reference signal from the CPLI 7. It is a comparator that compares with. 108 is a semiconductor laser, 109 is a collimator lens that collimates the light beam, 11 is a non-polarizing beam splitter, and 17 is a non-polarizing beam splitter.
2 is a spherical lens, 13 is a cylindrical lens, and 28 is a sensor provided with an information reproducing sensor and a semiconductor light emission amount control sensor.

In response to a command from the CPU 7, the signal to be recorded is sent to the laser control unit 3 via the interface 1 and the encoder 2, and the laser driver 4 modulates the semiconductor laser 108 based on the result. The light beam emitted from the semiconductor laser 108 is converted into parallel light by a collimator lens 109, and after being subjected to amplitude splitting by a non-polarizing beam splitter 11, the transmitted light beam is sent to an optical card 1 by an objective lens III.
A light spot is focused on 01 and recording is performed.

The light beam reflected by the optical card +01 travels backward along the optical path, is reflected by the non-polarizing beam splitter 11, and then passes through the spherical lens 1.
2. The light passes through an astigmatism generating optical system consisting of a cylindrical lens 13 and reaches the light receiving section of the sensor 28.

On the other hand, the light beam reflected by the non-polarizing beam splitter 11 is reflected again by a reflecting surface 17 made of a dielectric material or the like formed on one of the output surfaces of the non-polarizing beam splitter 11, and then passes through the non-polarizing beam splitter II again. The light passes therethrough, follows the optical path indicated by the broken line, and reaches the light receiving section of the sensor 28. The reflecting surface 17 is inclined, so that the reflected light beam travels at a different angle from the light beam reflected by the optical card 101, and therefore, the light beam reflected by the optical card 101 also travels at the light receiving section of the sensor 28.
The light beam is focused at a different position from the reflected light beam from.

FIG. 2 shows the light receiving section of the sensor 28, in which 21 represents an information reproducing sensor and 23 represents a light emission amount control sensor. The information reproducing sensor 21 has a light receiving section 211.212.21a divided into four parts.

2] 4, at the center of which the light beam 20 reflected from the optical card 1.1 is focused. Then, in response to the output from each light receiving section, the light receiving section 21. The difference between the sum of the outputs of and 213 and the sum of the light receiving sections 21□ and 214 is used as a signal for autofocus control using the astigmatism method. In addition, the light receiving section 211
The difference between the sum of the outputs of and 21□ and the sum of the light receiving sections 213 and 214 is used as a signal for auto-tracking control using a push-pull method. Furthermore, the sum of outputs from the four light receiving sections is used as an information reproduction signal.

The luminous intensity control sensor 23 consists of a single light-receiving surface, and the light beam 22 reflected by the reflecting surface 17 is transmitted to the light-receiving surface.
is focused.

Referring again to FIG. 1, the output of the light emission control sensor 23 passes through the amplifier 5 and enters the comparator 6. On the other hand, in response to a command from the CPU 7, the interface 1 sends to the comparator 6 a reference signal indicating a suitable amount of light emission corresponding to each recording/reproduction state. The comparator 6 compares the two signals and sends the result to the laser control unit 3, and based on this signal, the laser control unit 3 controls the laser driver 4 to achieve a suitable light emission state.

As already mentioned, the feature of this embodiment is that the reflective surface 17 is arranged at an angle with respect to the chief ray of the light beam incident on the face. With this arrangement, the reflected light is optical card +01
The reflected light is directed toward the sensor 28 at a different angle from that of the reflected light, so that separation on the light-receiving surface is possible. In addition, the reflective surface 17
A part of the luminous flux reflected by the non-polarizing beam splitter II
The light beam is reflected by the semiconductor laser 108 and becomes a light beam heading toward the semiconductor laser 108. However, since this light beam also has a different angle from the light beam emitted from the semiconductor laser, it is not focused on the light emitting part of the semiconductor laser 108, and is therefore generated by recombination. Harmful phenomena such as laser noise can be prevented. Further, if necessary, it is also possible to block only this returning light at an appropriate position.

3 and 4 are diagrams for explaining a second embodiment of the optical head A according to the present invention. The difference between the embodiment shown in the figure and the first embodiment is that a diffraction grating 30 is used for auto-tracking control.
The point is to apply the three-beam method using . 3 differs from FIG. 1 in that, in addition to the addition of the above-mentioned diffraction grating 30, the inclination direction of the reflective surface 17' is different from that of the diffraction grating 30.
The direction is substantially perpendicular to the direction in which the three beams generated by the beam are arranged, and the arrangement of the light receiving surface of the sensor 28' is slightly different, as will be explained later with reference to FIG. Since the other members are the same as those in FIG. 1, they are given the same numbers and their explanations will be omitted.

FIG. 4 is a diagram showing the configuration of the light receiving section of the sensor 28'.

In the light receiving section, a light receiving section 21 divided into four parts for information reproduction and autofocus control, two light receiving sections 32 and 33 for auto tracking control, and a light receiving section 41 of a sensor for controlling light emission amount are preferably the same. It is arranged on a "substrate". The light beams 43, 44, and 45 reflected by the optical card +01 and condensed onto the light receiving sections 21, 32, and 33 are used for Ohif-1-cass control, auto-tracking control, and information reproduction. On the other hand, the light beams 34, 35, and 36 reflected by the reflecting surface 17' and condensed onto the light receiving section 41-L are used to control the amount of light emitted from the semiconductor laser.

As mentioned before, by tilting the reflecting surface 17', the luminous flux is 34.35
．． 36 is shifted in a direction substantially perpendicular to the direction in which the light beams 43, 44, and 45 are lined up, and the light is received at the condensing position.The distance between the light receiving parts is shortened, and the above sensors can be mounted on the same board. This is convenient for locating. Also,
The reflecting surface 15' and the amplitude splitting surface of the beam splitter form a so-called two-mirror structure and reflect the light beam, so they are less susceptible to position setting errors during assembly of the beam splitter 11, and the direction of the light beam toward the sensor 28' is Always constant. Therefore, the light receiving sections 4I and 21, 32, 33 can be arranged in advance on the same substrate at a predetermined interval, which facilitates the adjustment work.

The sensor 41 used to control the amount of light emitted has a structure in which a single light-receiving section receives three light beams 34, 35, and 36, but this is because fluctuations in diffraction efficiency due to mode hops of the semiconductor laser 108, etc. Even if there is, the sum of the light amounts of a plurality of light beams is received, which is advantageous because it is less susceptible to the above fluctuations. Of course, the light receiving section may be divided into individual light receiving sections corresponding to each of the light beams 34, 35, and 36, and a sum signal of these sections may be obtained later.

The signal detected by the light receiving section 41 is inputted to the amplifier 5 in FIG. 3 as a light emission amount control signal, and the light emission amount of the semiconductor laser 108 is stably controlled through the same process as in the first embodiment. .

A third embodiment of the optical head Δ of the present invention will be described with reference to FIGS. 5 and 6. The feature of this embodiment is that a 21-conductor laser array 51 having a plurality of light emitting points, each of which can be driven independently, is used as a light source. A plurality of light beams from the semiconductor laser array 51 are reflected by the optical card +01, and as shown in FIG. has roles such as information recording/reproduction autofocusing control, autotracking control, reproduction confirmation of recorded information, and foreign object detection on the optical card 101. On the other hand, after passing through the collimator lens +09, the light beam reflected by the non-polarizing beam splitter 11 is reflected by the same reflecting surface 17' as in the second embodiment, and the light beam reflected by the optical card 101 is different from the light beam emitted by the semiconductor laser array 51. The light becomes a light beam having an angle in a direction substantially perpendicular to the arrangement of points, and is separately focused on the light receiving sections 7, 72 and 73 on the sensor 50, and generates a signal for controlling the amount of light emitted. Light receiving section 7], 72.7
3 is provided independently corresponding to each light beam, unlike the second embodiment. Therefore, the amount of light emitted from each light emitting section can be detected without being affected by the amount of light emitted from adjacent semiconductor lasers. The output from each light receiving section 71, 72.73 is an amplifier 53.5□, 5. The light is then sent to the comparator 6 through the tube 1 or the same procedure as in the second embodiment, making it possible to independently control the output of each light emitting point of the semiconductor laser array 51.

Next, an embodiment of the optical head 13 according to the present invention will be described.

FIG. 7 is a block diagram showing the configuration of a first embodiment of the optical head B according to the present invention. This figure shows an optical head that uses an astigmatism method for focus control and a push-pull method for tracking control.

In the figure, +08 is a semiconductor laser, +09 is a collimator lens for collimating the light beam emitted from the semiconductor laser, 10 is a shaping prism for shaping the cross section of the light beam into a substantially circular shape, 11 is a beam splitter, 111 is an objective lens, 101 is an optical card, 12 is a spherical lens, 1
3 is a cylindrical lens, 14 is a sensor for information reproduction, 15 is a sensor for controlling the amount of light emitted, and 16 is a reflecting mirror. Also,
4 is a laser driver circuit for driving the semiconductor laser 108, 6 is a comparator, 25 is a reference signal for driving the laser that is input to the comparator 6, and 5 is an amplifier for amplifying the output of the sensor for controlling the amount of light emission. I can't fix the circuit.

Hereinafter, a method of controlling the amount of light emitted by such an optical head will be explained in order.

Emitted from the semiconductor laser 108, collimator 109,
The light beam that has passed through the shaping prism] 0 is split by a beam splitter 11 into transmitted light and reflected light. The reflected light is focused into a light spot on the medium surface of the optical card 101 by the objective lens Ill, and information is recorded in the form of pits while moving the light spot and the optical card relatively using a drive mechanism (not shown). . The light beam reflected on the medium surface of the optical card 101 is
The optical path travels backwards, passes through the beam splitter 11, and then passes through the spherical lens 12 and the cylindrical lens I3 to the information reproducing sensor 1.
4 to obtain information signals, signals for focus control, and tracking control.

On the other hand, after passing through the shaping prism 10, the light beam transmitted through the beam splitter II is reflected by the reflecting mirror 16, and as shown by the broken line in the figure, the light beam travels backward along the optical path reaching the reflecting mirror, and then passes through the collimator lens 109. The light is focused and incident on the light emission amount control sensor 15. The reflective surface of the reflective mirror 16 is formed by depositing a dielectric film or the like, and preferably has a reflectance as high as possible for laser light. Further, the reflecting mirror 16 is fixedly installed with a slight inclination in order to cause the reflected light to enter the light emission amount control sensor I5 provided near the semiconductor laser.

The optical signal detected by the light emission amount control sensor 15 is amplified by the amplifier circuit 5 and then input to the comparator 6. On the other hand, a reference signal 25 indicating a suitable amount of light emission corresponding to the recording and playback conditions is inputted to the comparator from a -L position control device (not shown), and these two input signals are compared to determine the final value. Feedback control is applied to the laser driver 4 so that the amount of light emitted from the semiconductor laser reaches a desired state.

Here, if the optical card 101 has birefringence as described above, in order to avoid variations in the amount of light reaching the information reproducing sensor 14 due to birefringence, the beam splitter 11 is connected to a non-polarized beam. It is preferable to use a splitter.

Further, the light emission amount control sensor 15 can be built into the semiconductor laser 108 and integrated therewith.

An advantage of the present invention is that the collimator lens 109 also serves as a condensing lens for the sensor 15 for controlling the amount of received light, as can be seen from the explanation in section 1-.

Therefore, a sufficient amount of light can be obtained without the need to provide a new condensing lens, and a good signal-to-noise ratio can be maintained.

FIG. 8 is a block diagram showing the configuration of a second embodiment of the optical head B according to the present invention. The configuration shown in this figure is almost the same as that in FIG. 7, but the difference is that the objective lens 111 is placed on the side of the light beam that has passed through the beam splitter 11, and that the reflecting mirror 16 is replaced by -. As shown in the figure, it is a so-called two-panel mirror having two reflective surfaces. In this case, the light beam reflected by the beam splitter 11 is not returned to the light emission amount control sensor 15 by the reflection mirror 16.

If the configuration of the optical head requires that the objective lens III be placed in the position indicated by ``-'', it will be placed in such a position. Furthermore, by setting the angle between the two reflective surfaces of the reflective mirror 16 to be slightly deviated from a right angle, the light beam incident from the semiconductor laser side is always relative to the incident light beam, regardless of its direction. The return light forms a certain angle. Therefore, if the light emission amount control sensor 15 is integrated with the semiconductor laser 108 in advance at a certain distance, the position adjustment is easy because the returning light is always focused on the sensor.

FIGS. 9(a) and 9(b) are block diagrams showing the configuration of a third embodiment of the optical head B according to the present invention. In the figure, descriptions of members assigned the same numbers as in FIG. 7 will be omitted.

This embodiment differs from the embodiment shown in FIG. 7 in that instead of providing a reflecting mirror 16, the surface 17 of the prism constituting the beam splitter +1 is used as a reflecting surface. Further, the light emission amount control sensor 15 is housed inside the semiconductor laser, as shown in FIG. 9(b).

FIG. 9(b) shows the semiconductor laser 108 viewed from the optical axis direction, with 108-1 showing the mount, +08-2 showing the submount, and +08-3 showing the laser emitting section. The light emission control sensor 15 is provided on the mount +08-1 at a predetermined distance from the laser light emitting unit +08-3. The light emission control sensor 15 can be formed using a method similar to that of providing a photodiode for monitoring the light amount behind a semiconductor laser in a normal semiconductor laser. Also, the position in the forward axis direction is the laser emitting part +08
-3 does not need to be exactly in the same plane, and can be set arbitrarily within the range in which the returning light can be detected, as will be described later.

In this embodiment, one side 17 of the beam splitter 11
By forming a metal or dielectric reflective film on the first
There is no need to provide a new reflecting mirror 16 as in the embodiment described above, and therefore the same effect can be obtained without increasing the number of parts. By making one surface of the beam splitter 11 a reflective surface in this way, it has the effect of becoming mechanically stable.

To give a numerical example, for example: Focal length of collimator lens... f e =4.
5mm ・Shaping ratio of shaping prism...γ=2 ・Half mirror surface of beam splitter 11 and reflecting surface 17
When the angle θ = 46° and the refractive index of the beam splitter prism n = 1.5, the position β where the returned light shown by the broken line is imaged by the collimator lens is measured from the laser emitting part,
Approximately, A=2ny・fetan(θ-45°)
470 (μm), which is a size that allows a sensor for controlling the amount of light emission to be easily enclosed within the semiconductor laser package. In addition,
Since the purpose of this light emission control sensor is simply to detect the amount of light, even if it receives light that returns at an angle of incidence that exceeds the angle of view characteristics indicated by the design specifications of the collimator lens, the resulting image cannot be formed. Performance degradation is negligible.

In addition, there is also light that returns toward the information reproducing sensor 14 by the reflecting mirror 16 and reflecting surface 17 used in the embodiment, but as already explained, the reflecting surface (reflecting mirror 16, reflecting surface 17 provided on the beam splitter) (including the surface 17) are tilted so that no light is directly incident on the sensor 14. Alternatively, if necessary, it is also possible to block light during the canter.

[Effects of the Invention] As explained above using the embodiments, according to the optical head A and the optical head B according to the present invention, there is no need to newly provide a lens for condensing light, and a simple planar reflection lens is not required. By simply adding one surface, a sufficient amount of light can be detected and a stable signal with a good S/N ratio can be obtained.

■The combination of a reflective surface and a beam splitter makes it possible to easily adjust the position of the sensor for controlling the amount of light emitted by constructing a two-mirror structure.

It has the characteristics of a cap, and therefore has the effect of stabilizing the amount of laser light emission without increasing the weight or complicating the structure compared to conventional optical heads.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a first embodiment of an optical head A according to the present invention, and FIG. 2 is a diagram showing a sensor used in the optical head. FIG. 3 is a block diagram showing the configuration of a second embodiment of the optical head A according to the present invention, and FIG. 4 is a diagram showing a sensor used in the optical head. FIG. 5 is a block diagram showing the configuration of a third embodiment of the optical head A according to the present invention, and FIG. 6 is a diagram showing a sensor used in the optical head. 7, 8, and 9(a) respectively show the first part of the optical head B related to the water defense. Second. Third. It is a block diagram showing the configuration of the embodiment, and FIG. 9(b) is a diagram showing the semiconductor laser and sensor of the third embodiment. FIG. 10 is a diagram for explaining the optical card recording/reproducing device. FIG. 11 is a diagram for explaining the optical card. DESCRIPTION OF SYMBOLS 1... Interface, 2... Encoder, 3... Laser control part, 4... Laser driver, 5... Amplifier, 6... Comparator, 7... CPU. 108... Semiconductor laser, 109... Collimator lens, 11... Beam splitter, 12... Spherical lens, 13... Cylindrical lens, 14... Sensor for information reproduction, 5... Light emission Quantity control sensor, 6...Reflection mirror 7...Reflection surface, 01...Optical card, 11...Objective lens.

Claims (7)

[Claims] (1) A semiconductor laser as a light source, a collimator lens, a non-polarizing beam splitter, an objective lens, a first photodetector,
It has at least a condensing lens for condensing light on the first photodetector and a second photodetector, and optically converts the emitted light beam from the semiconductor laser, which is collimated by the collimator lens. An optical head that records and/or reproduces information by illuminating an information recording medium, dividing the amplitude of the reflected light by the non-polarizing beam splitter, and guiding the reflected light to the first photodetector via the condenser lens. The optical head has a reflective surface for reflecting a light beam that is not directed toward the optical information recording medium out of the light beam amplitude-split by the non-polarizing beam splitter, and the light beam reflected by the reflective surface is An optical head characterized in that the second photodetector is provided at a position where light is focused by the condenser lens, and the output of the semiconductor laser is controlled using the output of the photodetector. (2) The non-polarizing beam splitter is a rectangular parallelepiped prism with an amplitude splitting surface joined therebetween, and the reflecting surface does not direct the light beam split by the amplitude splitting surface toward an optical information recording medium. 2. The optical head according to claim 1, wherein the surface is a surface on which a light beam is incident. (3) The optical head according to claim 1, wherein the second photodetector is integrally formed on the same substrate as the first photodetector. (4) Semiconductor laser as a light source, collimator lens,
A beam emitted from a semiconductor laser, which includes at least a non-polarizing beam splitter, an objective lens, a first photodetector, the first photodetector, and a second photodetector, and is collimated by the collimator lens. irradiate the optical information recording medium with
An optical head for recording and/or reproducing information by splitting the amplitude of the reflected light by the non-polarizing beam splitter and guiding it to the first photodetector, wherein the non-polarizing beam splitter is the optical information recording head. The second photodetector is provided at a position where the light beam reflected by the reflection surface is focused by the collimator lens, the second photodetector having a reflective surface for reflecting a light beam not directed toward the medium, An optical head characterized in that the output of the semiconductor laser is controlled using the output of the semiconductor laser. (5) The optical head according to claim 1 or 4, wherein the reflective surface is provided at an angle with respect to the principal ray of the light beam that does not go toward the optical information recording medium. (6) The reflecting surface is composed of two mirrors, and the two mirrors reflect the emitted light beam from the semiconductor laser in a direction substantially the same as the traveling direction of the light beam in the opposite direction. Optical head described in section. (7) The optical head according to claim 4, wherein the second photodetector is integrally formed near a light emitting part of the semiconductor laser.