JP2008027546A - Composite optical element and optical signal reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To monitor some of the light emitted from the front surface of a light emitting element without making the whole device larger. <P>SOLUTION: This composite optical element 1 has a prism 4 and a light emitting element 6 facing this prism on a substrate 3 and signal detecting photo detectors PD1, PD2 formed under the prism on the substrate. An incident surface 4a of the prism for receiving some of the light of the light emitting element and a light transmissive section 4e at the other side to pass the light entered through the incident surface 4a are formed and the monitor photo detector M-PD is formed in the location facing the light transmissive section. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a novel composite optical element and an optical signal reader. More specifically, the present invention relates to a technique for improving the efficiency of monitoring the light emission output for setting the light emission output of the light emitting element to a desired value.

  Conventionally, as a composite optical element, for example, a laser coupler in which a light emitting unit and a signal detection unit in an optical signal reading device such as a compact disc (Compact Disc = CD) player are integrated is known.

  The laser coupler has a structure as shown in FIG. That is, in the laser coupler a, a microprism c and a so-called LOP (Laser On Photodiode) chip f on which a semiconductor laser e is mounted on a photodiode d are mounted adjacent to each other on a photodiode ICb as a base. . On the photodiode ICb, signal detection photodiodes g1 and g2 are formed side by side (in the arrangement direction of the microprism c and the LOP chip f), and the microprism is disposed on the two photodiodes g1 and g2. c is mounted. Further, on the photodiode ICb, a current-voltage (IV) conversion amplifier of the output current signals of the photodiodes g1 and g2, an arithmetic processing unit, and the like are formed as an IC.

  The microprism c opposes the semiconductor laser e and has an inclined surface c1 formed as a half mirror to form an incident surface, an upper surface c2 formed with a total reflection surface, a rear surface c3 formed with a light absorption film, and below the inclined surface c1. And has a front end surface c4 formed in a mirror surface.

  The S-polarized laser beam L1 emitted from the front surface of the semiconductor laser e is reflected by the inclined surface c1 of the microprism c, rises in the vertical direction, and moves up by one point via a quarter wavelength plate (not shown) and an objective lens (not shown). Recording light that travels sequentially, for example, a pit formed in a track shape of an optical disk such as a CD, and the return light L2 reflected by the signal recording element and made P-polarized follows the same optical path in the reverse direction to form a microprism. The half light incident on the micro prism c from the inclined surface c1 of c and transmitted through the half mirror formed on the photodiode g1 is received by the photodiode g1 and reflected by the half mirror on the photodiode g1. The half of the reflected light is further reflected by the total reflection surface on the upper surface and received by the photodiode g2, thereby signal recording. Recorded signal under is read.

  A predetermined laser output is required for reading the signal or writing the signal to the recording medium to the optical disk or the like. Therefore, in the laser coupler or the like described in Patent Document 1, the light output from the rear end surface of the semiconductor laser e is monitored by the photodiode d, whereby the light output L from the front end surface becomes a desired value. It is used as a guideline for control.

JP 2004-134005 A

  By the way, in order to cope with an improvement in recording speed, an increase in recording depth (for example, recording in a deep layer in a two-layer recording method), etc. in an optical signal reading device (including the device capable of recording in the term of the reading device). Therefore, there is a demand for higher laser output. The increase in laser output is accompanied by an increase in the cavity length of the semiconductor laser, and there is no room behind the semiconductor laser e on the LOP chip, so that the photodiode d receives light emitted from the rear end surface of the semiconductor laser e. It is difficult to secure the surface to be used. In order to be able to receive the light emitted from the rear end face of the semiconductor laser with the increased resonator length, the photodiode d must be enlarged, and the laser coupler must be enlarged.

  In addition, a monitoring photodiode is formed at a position between the micro prism c on the upper surface of the photodiode ICb and the LOP chip, and a part of the light emitted from the front end surface of the semiconductor laser e is transferred to the front end surface c4 of the micro prism c. Although there is a technique of reflecting the reflected light and monitoring the reflected light by the monitoring photodiode, the increase in the output of the laser is accompanied by the narrowing of the radiation angle, and it is difficult to obtain the emitted light for monitoring.

  In view of the above circumstances, an object of the present invention is to enable monitoring of a part of light emitted from the front end face of a light emitting element without requiring an increase in the size of the entire apparatus.

  A composite optical element according to an embodiment of the present invention includes a prism on a base, a light emitting element disposed to face the prism, and a light receiving element for signal detection formed on the base below the prism, Forming a light transmitting portion through which light of the light emitting element incident from the incident surface is transmitted at a portion of the prism located on a side opposite to the incident surface on which a part of the light of the light emitting element is incident; A light-receiving element for monitoring is formed at a position facing the light transmission part.

  An optical signal reader according to an embodiment of the present invention includes a prism on a substrate, a light emitting element disposed opposite to the prism, and a light receiving element for signal detection formed on the substrate below the prism. And an optical element that guides the light emitted from the light emitting element to a recording medium on which a signal recording element that modulates and reflects the irradiated light is formed, and the light emission by the optical element Return light modulated by irradiating the signal recording element that sequentially travels on one point with the light of the element and reflected by the signal recording element is incident on the prism, and further received by the light receiving element for signal detection In the optical signal reading device, the light of the light emitting element incident from the incident surface on a portion of the prism positioned on the side opposite to the incident surface on which a part of the light of the light emitting element is incident. A light-transmitting part is formed, a light-receiving element for monitoring is formed at a position on the substrate facing the light-transmitting part, and a part of the light of the light-emitting element received by the light-receiving element for monitoring is Monitor the light output.

  In the present invention, a part of the emitted light from the front end face of the light emitting element is received by the monitoring light receiving element.

  The best mode for carrying out the composite optical element and the optical signal reader according to the present invention will be described below with reference to the drawings.

  The composite optical element of the present invention is a composite optical element comprising: a prism on a substrate; a light emitting element disposed opposite to the prism; and a light receiving element for signal detection formed on the substrate below the prism. Forming a light transmitting portion through which light of the light emitting element incident from the incident surface is transmitted at a portion of the prism located on a side opposite to the incident surface on which a part of the light of the light emitting element is incident; A light-receiving element for monitoring is formed at a position facing the light transmission part.

  Therefore, in the composite optical element of the present invention, a part of the emitted light from the front end face of the light emitting element can be received by the monitor light receiving element. Therefore, for example, even when it becomes difficult to monitor the light emitted from the rear end face of the light emitting element due to the increase in output, the light emitted from the front end face of the optical element is increased without increasing the total length of the composite optical element. Auto power control is possible by monitoring the part.

  The composite optical element of the present invention can be implemented by the embodiments shown in the following (1) to (3).

  (1) A light guide part is formed between the light receiving element for monitoring and the light transmitting part. By forming the light guide section, it is possible to prevent light from scattering due to exiting from the prism into the air, and to allow the monitor light receiving element to receive a desired proportion of light emitted from the light emitting element. .

  (2) The prism is bonded and fixed on the base with an ultraviolet curable resin, and the ultraviolet curable resin protruding from between the bottom surface of the prism and the base is between the light receiving element for monitoring and the light transmitting portion. The light guide part is formed by curing. In order to form the light guide part, different materials and processes are not required, and the light guide part can be formed in the process of fixing the prism to the base.

  (3) A transmittance adjusting film is formed on the light transmitting portion. By selecting the transmittance of the transmittance adjusting film, a desired proportion of the light emitted from the light emitting element can be received by the monitoring light receiving element.

  In addition, above-described embodiment (1)-(3) is a typical example of the embodiment of this invention composite optical element, Comprising: Implementation by other embodiments is not prevented.

  Next, the composite optical element of the present invention will be described more specifically. In the following embodiments, the composite optical element of the present invention is applied to a laser coupler.

  First, FIG. 1 shows an outline of a laser coupler.

  The laser coupler 1 is accommodated in, for example, a ceramic flat package 2 and the open upper surface of the flat package 2 is sealed with a transparent window cap (not shown).

  Next, details of the laser coupler will be described.

  FIG. 2 is a sectional view showing the first embodiment.

  In the laser coupler 1, a microprism 4 is mounted on a photodiode IC 3 that is a base, and a submount base 5 is mounted at a position facing the microprism 4 on the photodiode IC3. A semiconductor laser 6 is mounted as a light emitting element.

  In the microprism 4, a slope 4 a is formed at a position facing the semiconductor laser 6 at an angle of approximately 45 ° with respect to the laser beam emission direction of the semiconductor laser 6, and a half mirror film (not shown) is formed on the slope 4 a. Is formed. Further, a total reflection film (not shown) is formed on the upper surface 4b of the microprism 4, and a light absorption film 4d is formed on the rear surface 4c located on the side opposite to the inclined surface 4a. Further, an antireflection film (not shown) is formed on the lower surface of the microprism 4. A light transmitting portion 4e on which the light absorbing film 4d is not formed is formed at the lower end portion of the rear surface 4c.

  Two signal detection photodiodes PD1 and PD2 are formed side by side in the laser beam emission direction of the semiconductor laser 6 as a signal detection light receiving element at a position facing the lower surface of the microprism 4 on the upper surface of the photodiode IC3. In addition, a monitoring photodiode M-PD is formed as a monitoring light receiving element at a position corresponding to the rear of the light transmitting portion 4e of the microprism 4. A half mirror is formed on the upper surface of the signal detection photodiode PD1. The opening width Wh of the light transmission part 4e is preferably 10 to 300 μm.

  As will be described later, the signals recorded on the recording medium and the tracking error signal are detected by the two signal detection photodiodes PD1 and PD2, and the semiconductor laser 6 is detected by the monitor photodiode M-PD. The power of laser light emitted from the front surface of the semiconductor laser 6 is detected, and auto power control of the semiconductor laser 6 is performed based on the detection result. Further, the photodiode IC3 is formed by integrating a current-voltage (IV) conversion amplifier of the output current signals of the photodiodes PD1, PD2, and M-PD, an arithmetic processing unit, and the like.

  A transparent light guide 7 is formed between the light transmitting portion 4e of the microprism 4 and the monitoring photodiode M-PD, and the light guiding portion 7 includes the light transmitting portion 4e and the monitoring photodiode M-. It is in close contact with the PD. The light guide 7 may be formed separately from the microprism 4 or may be formed integrally with the microprism 4, but the microprism 4 may be a photodiode. A part of the ultraviolet curable resin for mounting on the IC 3 protrudes behind the microprism 4 and is shaped so that the protruding ultraviolet curable resin is in close contact with the light transmitting portion 4e and the monitoring photodiode M-PD. By forming them, the light guide 7 can be formed in the process of fixing the prism to the base body without requiring different materials and processes, and the cost can be reduced. Further, when the microprism 4 is formed of an optical glass having a refractive index of about 1.75, the refractive index is approximately 1.5 and the refractive index of the ultraviolet curable resin is preferable.

  The case where the operation of the laser coupler 1 is applied to a CD player CDDV as an optical signal reader will be described as an example.

  The optical signal reading apparatus of the present invention is a composite optical system comprising a prism on a base, a light emitting element disposed opposite to the prism, and a signal detecting light receiving element formed on the base below the prism. And an optical element that guides the light emitted from the light emitting element to a recording medium on which a signal recording element that modulates and reflects the irradiated light is formed, and the light from the light emitting element is 1 by the optical element. Optical signal received by the signal detection light-receiving element, and the return light modulated by irradiating the signal recording element traveling sequentially on the point and being reflected by the signal recording element is incident on the prism. In the reading device, a light transmitting portion through which light of the light emitting element incident from the incident surface is transmitted to a portion of the prism located on a side opposite to the incident surface on which a part of light of the light emitting element is incident. Forming a light receiving element for monitoring at a position on the substrate facing the light transmitting portion, and monitoring a light emission output of the light receiving element by a part of light of the light emitting element received by the light receiving element for monitoring It is.

  In the CD player CDDV shown in FIG. 2, most of the S-polarized laser light L1 emitted from the semiconductor laser 6 is reflected on the inclined surface 4a of the microprism 4 by L1, for example, 70%, and rises in the vertical direction. For example, 30% is incident on the micro prism 4. The laser light Lm incident in the microprism 4 is directed to the light transmission part 4e, most of the light is transmitted through the light transmission part 4e, and further passes through the light guide part 7 and is received by the monitoring photodiode M-PD. . Based on the laser light Lm received by the monitoring photodiode M-PD, the output power of the semiconductor laser 6 is detected. Based on the detection result, the output power of the semiconductor laser 6 is set to a desired value to the semiconductor laser 6. The amount of current to be applied is adjusted, and auto power control is performed.

  On the other hand, the laser beam L1 reflected by the inclined surface 4a of the microprism 4 and rising in the vertical direction is irradiated onto the recording surface CDa of the compact disc CD via the quarter-wave plate QP and the objective lens OL, and formed on the recording surface CDa. The reflected light L2 reflected by the signal recording element, passed through the objective lens OL, and made P-polarized by the quarter-wave plate QP enters the microprism 4 from the inclined surface 4a of the microprism 4, and 50% is the signal first. Light is received by the detection photodiode PD1, and the remaining 50% is reflected by the half mirror on the photodiode PD1, and further reflected by the total reflection surface of the upper surface 4b and received by the signal detection photodiode PD2.

  In FIG. 2, a quarter-wave plate QP and an objective lens OL are used as optical elements for guiding laser light from the laser coupler 1 to the signal recording surface CDa of the compact disc CD and from the signal recording surface CDa to the laser coupler 1. Only an optical signal reading apparatus such as an actual CD player is provided with optical elements other than a quarter-wave plate QP and an objective lens OL, such as a mirror such as a rising mirror. In addition, in this specification, the term optical signal reading device is a so-called optical signal that reads a signal recorded on a recording medium, that is, only performs reproduction, and also records a signal on a recording medium. It is used to include a recording / reproducing device.

  Furthermore, the recording medium is not limited to an optical disc such as a CD or a DVD (Digital Versatile Disc), but includes other forms of optical recording media. Furthermore, the signal recording element recorded on the recording medium is relatively traveling, for example, the irradiation position of the laser beam is fixed (the fine movement during tracking and focusing is considered fixed) and the signal recording element is In addition to the case where the signal recording element moves, even if the signal recording element is fixed and the irradiation position of the laser light is moved in the arrangement direction of the signal recording element by, for example, a galvanomirror device, Are included in the definition of “signal recording element that travels sequentially”.

  FIG. 3 shows a second embodiment in which the composite optical element of the present invention is applied to a laser coupler.

  The laser coupler 11 according to the second embodiment is related to the first embodiment in that a transmittance adjusting film 18 having an appropriate light transmittance is formed on the light transmitting portion 4e of the microprism 4. Unlike the laser coupler 1, the other points are the same as those of the laser coupler 1 according to the first embodiment. Accordingly, the same parts as those of the laser coupler 1 according to the first embodiment are denoted by the same reference numerals as those of the laser coupler 1 according to the first embodiment, and the description thereof is omitted. .

  As described above, by forming the transmittance adjusting film 18 in the light transmitting portion 4e, the amount of light received by the monitoring photodiode M-PD can be arbitrarily set, and the monitoring accuracy can be improved. it can.

  FIG. 4 shows a modification of the second embodiment. The laser coupler 11A according to this modification is different from the laser coupler 11 in the method of forming the transmittance adjusting film. That is, in the laser coupler 11, the light absorption film 4d once formed on the rear surface 4c of the microprism 4 is removed, or the light absorption film 4d is formed by masking the portion to be the light transmission portion 4e of the rear surface 4c. Thus, the light transmission portion 4e is formed, and then the transmittance adjustment film 18 is formed only on the light transmission portion 4e (for example, by masking other portions). The laser coupler 11A according to this modification example In this case, after the light transmitting portion 4e is formed in the same manner as in the laser coupler 11, the light transmitting portion 4e is formed by forming the transmittance adjusting film 18 over the entire rear surface 4c (also on the light absorbing film 4d). Is covered with a transmittance adjusting film 18. By forming the transmittance adjusting film 18 on the entire rear surface 4c of the microprism 4 as in the laser coupler 11A, no extra work such as masking is required when forming the transmittance adjusting film 18, and the transmittance adjusting film 18 Even considering that extra material is required, the cost can be reduced.

  FIG. 5 shows a third embodiment in which the composite optical element of the present invention is applied to a laser coupler.

  The laser coupler 21 according to the third embodiment is different from the laser couplers 1 and 11 according to the first and second embodiments in the formation position of the light transmitting portion of the microprism 4. This is the same as the laser couplers 1 and 11 according to the first and second embodiments. Accordingly, the same parts as those of the laser couplers 1 and 11 according to the first and second embodiments are the same as the reference numerals assigned to the same parts of the laser couplers 1 and 11 according to the first and second embodiments. The description will be omitted by adding the reference numerals.

  An inclined surface 24 that is obliquely cut is formed at the lower end of the rear end of the microprism 4, and the inclined surface 24 is used as a light transmission portion. A light guide section 27 is formed between the light transmission section 24 and the monitoring photodiode M-PD, and the light guide section 27 is formed on the light receiving surfaces of the light transmission section 24 and the monitoring photodiode M-PD. It is in close contact. The opening width Ws of the light transmission part 24 is preferably 20 to 300 μm, and the inclination angle θ24 of the light transmission part 24 is preferably set to 5 to 70 °. Further, the light guide portion 27 can also be formed by a portion protruding from between the bottom surface of the microprism 4 of the ultraviolet curable resin for mounting the microprism 4 on the photodiode IC3 and the photodiode IC3.

  As described above, the lower end portion of the rear end portion of the microprism 4 is partly cut, and the light transmitting portion 24 is formed there, so that the monitoring photodiode M-PD facing the light transmitting portion 24 can be changed. It can be positioned more forward than in the first and second embodiments, that is, closer to the semiconductor laser 6, and accordingly, the length of the laser coupler 21, that is, the size in the arrangement direction of the semiconductor laser 6 and the microprism 4. Can be reduced.

  It should be noted that the shapes and structures of the respective parts shown in the above-described embodiments are merely examples of the embodiments for carrying out the present invention, and the technical scope of the present invention is limited thereby. It should not be interpreted.

It is a perspective view which shows the outline | summary of this invention composite optical element packaged in the flat package. 1 is an enlarged sectional view showing a first embodiment in which a composite optical element of the present invention is applied to a laser coupler. It is an expanded sectional view which shows 2nd Embodiment which applied the composite optical element of this invention to the laser coupler. It is an expanded sectional view showing the modification of a 2nd embodiment. It is an expanded sectional view which shows 3rd Embodiment which applied the composite optical element of this invention to the laser coupler. It is an expanded sectional view which shows an example of the conventional laser coupler.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Laser coupler (composite optical element), 3 ... Photodiode IC (base | substrate), 4 ... Micro prism (prism), 4a ... Slope (incident surface), 4e ... Light transmission part, 6 ... Semiconductor laser (light emitting element), 7 ... light guide, PD1 ... photodiode for signal detection (photodetector for signal detection), PD2 ... photodiode for signal detection (photodetector for signal detection), M-PD ... photodiode for monitor (monitor) Light receiving element), 11 ... laser coupler (composite optical element), 18 ... transmittance adjustment film, 11A ... laser coupler (composite optical element), 21 ... laser coupler (composite optical element), 24 ... light transmitting part, 27 ... Light guide unit, CDDV ... CD player (optical signal reader), QP ... quarter wave plate (optical element), OL ... objective lens (optical element), CD ... compact disc (recording medium)

Claims (5)

In a composite optical element comprising a prism on a substrate, a light emitting element disposed opposite to the prism, and a light receiving element for signal detection formed on the substrate below the prism,
Forming a light transmitting portion through which light of the light emitting element incident from the incident surface is transmitted at a portion of the prism located on a side opposite to the incident surface on which a part of the light of the light emitting element is incident; A composite optical element, wherein a light receiving element for monitoring is formed at a position facing the light transmitting portion. The composite optical element according to claim 1, wherein a light guide part is formed between the light-receiving element for monitoring and the light transmission part. The prism is bonded and fixed on the base by an ultraviolet curable resin,
The ultraviolet light curable resin that protrudes from between the bottom surface of the prism and the base is cured between the light receiving element for monitoring and the light transmitting portion to form the light guide portion. 2. The composite optical element according to 2. The composite optical element according to claim 1, wherein a transmittance adjusting film is formed on the light transmitting portion. A composite optical element comprising a prism on the substrate, a light emitting element disposed opposite to the prism, and a light receiving element for signal detection formed on the substrate below the prism;
An optical element that guides the light emitted from the light emitting element to a recording medium on which a signal recording element that modulates and reflects the irradiated light is formed;
The optical element irradiates the signal recording element that sequentially travels the light of the light emitting element on one point and is reflected by the signal recording element to be incident on the prism. An optical signal reader received by a light receiving element for detection,
Forming a light transmitting portion through which light of the light emitting element incident from the incident surface is transmitted at a portion of the prism located on a side opposite to the incident surface on which a part of the light of the light emitting element is incident; A light receiving element for monitoring is formed at a position facing the light transmitting portion,
An optical signal reading device, wherein the light emission output of the light receiving element is monitored by a part of the light of the light emitting element received by the monitoring light receiving element.

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