JP2009210528A - Light transmitting/receiving device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To raise the capture probability of plume of a material to be measured of space, to minimize the device, to reduce the price, and to efficiently condense the return light to a light receiver. <P>SOLUTION: This light transmitting/receiving device comprises a light source 22, a collimator lens 23 for converting the light emitted from the light source 22 into parallel light, a turning mirror 25 that has a reflecting section 28a reflected in response to the parallel light emitted from the collimator lens 23 and is formed so as to turn a part having the reflecting section 28a within a predetermined angle range, a transmitting/receiving lens 35 that has the focal point positioned near the incidence position of the parallel light to the turning mirror 25, receives the parallel light reflected by the reflecting section 28a, emits it to transmitting/receiving object space, and condenses the return light from the transmitting/receiving object space to the proximity of the focal point, and a light receiving element 40 that is fixed to a position that is near the focal point of the transmitting/receiving lens 35 in a part of the turning mirror 25 having the reflecting section 28a and is separated from the incidence position of the parallel light, and receives the return light from the transmitting/receiving object space. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical transmission / reception apparatus used for emitting light to a space, receiving light returning from the space with respect to the light, and grasping a physical influence on the light by the space. Can be scanned spatially, and by making the optical system for transmission and reception the same, the size and cost of the apparatus can be reduced, and the scanned light is scattered and reflected back to the light source direction. The present invention relates to a technique for allowing return light to be focused on a light receiver with high efficiency.

  As one of methods for detecting a predetermined physical quantity, a method for detecting a change in the spectrum of light is used. For example, since a substance has an electromagnetic wave absorption peak at a natural frequency corresponding to its crystal structure or molecular structure, the substance is irradiated with the electromagnetic wave, the spectrum of the transmitted wave is detected, and the electromagnetic wave absorbed by the substance is detected. The substance can be known by examining the frequency. Furthermore, the content and concentration of the substance can be quantified from the absorption rate.

  Since the above absorption peak is unique to each substance, only the target substance can be efficiently detected by using an electromagnetic wave having a frequency matched to the peak. As an element capable of emitting an electromagnetic wave having this specific frequency, a semiconductor laser can be cited. This is because the semiconductor laser not only emits light of a specific wavelength at a high energy density but also can emit electromagnetic waves in the infrared region where there are many natural frequencies (absorption peaks) of gas molecules. For this reason, if a semiconductor laser and a light receiver are combined, it is possible to measure the concentration of a specific gas molecule present in the atmosphere.

  Conventionally, electric sensors have been used as a method for measuring the concentration of a substance present in space. However, these electric sensors must be installed at a place where the target substance exists. For this reason, when using it for the purpose of detecting the leakage of a substance, etc., multipoint measurement is required so as not to overlook it, and the installation and wiring of the sensor are enormous.

  Therefore, in recent years, there is an interest in a measurement method using the light absorption peak as described above, which can easily measure the concentration of a substance over a wide space without requiring the installation of a sensor and wiring. In particular, when detecting and measuring flammable substances, it has attracted a great deal of attention because of its high explosion resistance.

  For example, in the following Patent Document 1, laser light is emitted from a laser element that oscillates at an optical frequency that matches the absorption peak of a substance to be measured in the direction of the measurement object, scattered and reflected by a wall, etc., and returned to the laser element direction. A method of measuring the concentration of a target substance existing between a wall and the like from a laser element by receiving the returned light with a light receiver is disclosed.

  In this method, light emitted from the semiconductor laser is converted into parallel light by a collimator lens and then propagated to space, and return light scattered and reflected by the wall or the like is collected on a light receiver by a condenser lens. The concentration of the target substance can be measured from the attenuation of light power at the absorption peak.

JP-A-2005-106521

  Substances that are leaked or discharged from a specific part of the pipe flow normally into the wind, so they become plumes (bands of high-concentration gaseous substances) rather than isotropically spreading and spread into the space. For this reason, the substance concentration in the vicinity of the plume is high, but when it is away from it, the concentration decreases extremely. In order to detect this plume using light, light must be emitted aiming at a certain direction of the plume.

  However, in the case of the prior art in which the light emitted from the semiconductor laser is converted into parallel light by the collimator lens and propagated to the space as described above, the cross section of the parallel light is kept thin, so that the space in which the gas concentration can be measured The range must be very limited.

  When using the method disclosed in Patent Document 1, it is possible to search for a space where a plume exists by gradually changing the direction in which the parallel light is emitted. However, if the location where the measurement target substance exists is far from the measuring instrument, even if the parallel light emission angle is changed slightly, the passage position of the parallel light will be greatly shifted. It is necessary to change the emission angle of parallel light with high accuracy.

  As a means for solving this problem, a method of controlling the emission direction of the parallel light with high accuracy by adding a movable mechanism to the measuring device can be considered. However, when an additional movable mechanism is added in this way, the apparatus becomes large and expensive, and in particular, a problem arises that it is impossible to provide a handheld inexpensive apparatus.

  In addition, a method of reflecting parallel light with a galvanometer mirror and changing its emission direction is also conceivable, but when a light transmission system and a reception system are configured separately as in the prior art such as Patent Document 1, Not only does the number of optical components increase and the apparatus becomes large and expensive, but the light receiving efficiency of the return light in the light receiver also decreases.

  The present invention solves the above problems and spatially sweeps the direction of the emitted light emitted from the light source, thereby improving the probability that the plume of the measurement target substance can be captured and making the transmission / reception optical system the same. In this way, the optical transmitter / receiver can reduce the size and cost of the device, and can condense the return light that returns to the light source direction as the scanned light is scattered / reflected. The purpose is to do.

In order to achieve the above object, an optical transmission / reception apparatus according to claim 1 of the present invention includes:
A light source (22);
A collimating lens (23) for converting light emitted from the light source into parallel light;
A rotating mirror having a reflecting portion (28a) that receives and reflects the parallel light emitted from the collimating lens, and is formed so that the portion provided with the reflecting portion can be rotated within a predetermined angle range. (25) and
The focal point is located in the vicinity of the incident position of the parallel light with respect to the rotating mirror, receives the parallel light reflected by the reflecting unit and emits the parallel light to the transmission / reception target space, and returns light from the transmission / reception target space to the focus. A transmitting and receiving lens (35) for condensing in the vicinity;
The rotating mirror is fixed at a position near the focal point of the transmission / reception lens at a portion where the reflection unit is provided and is spaced from the incident position of the parallel light, and is incident from the transmission / reception target space via the transmission / reception lens. And a light receiving element (40) for receiving the returned light.

An optical transceiver according to claim 2 of the present invention is the optical transceiver according to claim 1,
The light source is a semiconductor laser, and an isolator (24) is provided between the collimating lens and the rotating mirror in order to block the return light reflected by the rotating mirror and emitted in the direction of the light source. ).

An optical transceiver according to claim 3 of the present invention is the optical transceiver according to claim 1 or 2,
The rotating mirror is
An inner frame (27);
A reflector (28) disposed inside the inner frame and having the reflecting portion formed on one surface;
A first connecting shaft (31, 32) that is twistably deformable and that rotatably supports the reflector on the inner side of the inner frame;
The light receiving element is provided on the one surface side of the reflecting plate.

An optical transceiver according to claim 4 of the present invention is the optical transceiver according to claim 3,
An outer frame (26);
A second connecting shaft (29, 30) that is twistable and deformable in a direction different from the twisting direction of the first connecting shaft, and that rotatably supports the inner frame inside the outer frame; It is characterized by being.

An optical transceiver according to claim 5 of the present invention is the optical transceiver according to claim 3 or claim 4,
A counter mass (45) that balances a rotational moment generated by the light receiving element is fixed to the other surface of the reflecting plate of the rotating mirror.

Moreover, the optical transmission / reception processing apparatus of Claim 6 of this invention is the optical transmission / reception apparatus in any one of Claims 1-5,
A mask (50) is provided between the collimating lens and the rotating mirror so that the light emitted from the collimating lens does not reach the light receiving element.

  With this configuration, the optical transmission / reception apparatus of the present invention can spatially repeatedly sweep the emission direction of the light emitted from the light source and converted into parallel light by the collimator lens, and exists in the transmission / reception space. The probability that the plume of the measurement target substance to be captured can be captured is greatly improved, and the spatial distribution of the measurement target substance can be measured.

  In addition, since the optical system for transmission and reception is shared, the size and cost of the device can be reduced without increasing the number of optical components, and the return light of the spatially scanned light can be reduced with fewer optical components. Since the light can be efficiently collected on the light receiver, it is possible to measure a high signal-to-noise ratio and improve the measurement accuracy of the target substance concentration.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows the structure of an optical transceiver 20 to which the present invention is applied.

  The optical transmitter / receiver 20 is configured by fixing a semiconductor laser 22 as a light source, a collimator lens 23, an isolator 24, a rotating mirror 25, and a transmitter / receiver lens 35 on a base 21.

  The semiconductor laser 22 emits light of a wavelength corresponding to the absorption wavelength of the substance to be measured in the transmission / reception target space to the collimator lens 23, and the collimator lens 23 converts the emitted light of the semiconductor laser 22 into parallel light and converts it to the base 21. The light is emitted to a rotating mirror 25 via an isolator 24 along an optical axis substantially parallel to the upper surface. The semiconductor laser 22, the collimating lens 23, and the isolator 24 are fixed on a base 21a having a predetermined height. The isolator 24 prevents the return light from the rotating mirror 25, in particular, the laser light of the semiconductor laser 22 returning from the transmission / reception target space, which will be described later, from returning to the semiconductor laser 22 and causing laser oscillation to become unstable.

  The rotating mirror 25 has a reflecting portion 28a that receives and reflects the parallel light emitted from the collimating lens 23, and is formed so that the portion provided with the reflecting portion can be rotated within a predetermined angle range. ing.

  As the rotating mirror, a one-axis structure that scans the space on a line and a two-axis structure that scans the space two-dimensionally can be used. Here, the two-axis is used so that the space can be inspected more efficiently. The structure will be described.

  The rotating mirror 25 has a gimbal structure having two axes (X axis and Y axis) orthogonal to each other in the same plane, and an outer frame 26, an inner frame 27, and a reflector 28 are used by etching the semiconductor substrate. In addition, it has a so-called MEMS structure in which the outer connecting shafts 29 and 30 and the inner connecting shafts 31 and 32 are integrally formed.

  As shown in FIG. 2, the outer frame 26 of the rotating mirror 25 is formed in a rectangular frame shape by an upper plate 26a, a lower plate 26b, and left and right side plates 26c, 26d, and an upper plate 27a and a lower plate 27b are disposed on the inside thereof. A rectangular frame-shaped inner frame 27 composed of left and right side plates 27c and 27d is concentrically disposed, and a rectangular reflector 28 is concentrically disposed inside thereof.

  The center of the inner edges of the side plates 26c, 26d of the outer frame 26 and the center of the outer edges of the side plates 27c, 27d of the inner frame 27 are connected by outer connecting shafts 29, 30 having torsionally deformable thinness. Between the center of the inner edge of the upper plate 27a and the lower plate 27b and the center of the upper and lower edges of the reflecting plate 28 are connected by inner connecting shafts 31 and 32 having a torsionally deformable thinness.

  Therefore, the reflecting plate 28 is supported so that it can be rotated about two orthogonal axes with the intersection of the line connecting the outer connecting shafts 29 and 30 and the line connecting the inner connecting shafts 31 and 32 to the outer frame 26 as the center of rotation. Has been.

  Although not described in detail here, the rotation drive of the inner frame 27 with respect to the outer frame 26 and the rotation drive of the reflection plate 28 with respect to the inner frame 27 may be either an electrostatic drive method or an electromagnetic drive method.

  The electrostatic drive method uses a suction force generated between the electrodes by applying a voltage to the opposing electrodes. In the case of the above structure, the electrode formed on at least one end side in the left-right direction of the reflector 28; A voltage is applied between the electrodes fixed to the inner frame 27 so as to oppose it, and the reflecting plate 28 is rotated with respect to the inner frame 27 using the inner connecting shafts 31 and 32 as rotation axes. A voltage is applied between an electrode formed on at least one end in the vertical direction of the inner frame 27 and an electrode fixed to the outer frame 26 so as to face the inner frame 27. Are rotated with the outer connecting shafts 29 and 30 as pivot axes.

  In the case of the electromagnetic drive system, the inner frame 27 and the reflection plate 28 are rotated using any combination of an electromagnet and a magnetic body, electromagnets or electromagnets and permanent magnets instead of the counter electrode.

  The direction of the reflecting plate 28 with respect to the outer frame 26 can be arbitrarily changed within a predetermined range by a signal for rotational driving, and thereby the scanning trajectory of light with respect to the space can be freely set.

  For example, if the biaxial drive signal is a sine wave signal having the same frequency and a phase difference of 90 degrees, the scanning trajectory of the emitted light can be made circular (or elliptical) as shown in FIG. If a frequency difference is given to the two drive signals, scanning of a rectangular space by a combination of scanning in the horizontal direction and the vertical direction as shown in FIG. 3B (this example is coarse scanning, but uniform scanning may be used. ) Is also possible.

  In the case of performing only one-dimensional scanning, a configuration in which the outer frame 26 and the outer connecting shafts 29 and 30 are removed from the rotating mirror 25 having the above configuration can be handled. Of course, in the rotating mirror 25 having the above-described configuration, the one-dimensional scanning can be performed by rotating the reflecting plate 28 in a state where the inner frame 27 is fixed to the outer frame 26.

  The rotating mirror 25 having such a structure is fixed with the outer frame 26 standing upright on a base 21b having a predetermined height, and reflects the parallel light emitted from the collimating lens 23 through the isolator 24. The light is received by a reflecting portion 28a formed at a position slightly away from the center of 28 and so as to exhibit a high reflectance with respect to light.

  Here, the case where the reflection portion 28a is formed only in the region where the parallel light is incident will be described. However, the reflection portion 28a exhibiting a high reflectance with respect to the light has a region where the parallel light is incident. It can be formed in an arbitrary area as long as it is a region excluding a portion where a light receiving element 40 described later is provided.

  The light is incident from the outside space through a transmission / reception lens 35 (described later) at a position slightly below the center of the surface of the reflecting plate 28 of the rotating mirror 25 (a distance approximately equal to the distance from the center to the reflecting portion 28a). A light receiving element 40 for receiving the received light is formed.

  The light receiving element 40 has a current-voltage conversion circuit (IV conversion circuit) inside, and outputs a signal having a voltage proportional to the intensity of incident light. The light receiving element 40 is formed separately from the rotating mirror 25 and fixed to the surface of the reflecting plate 28 in addition to the light receiving element 40 formed integrally with the surface of the reflecting plate 28 by the semiconductor technology in the manufacturing process of the rotating mirror 25. It may be what was done. However, when the light receiving element 40 is integrally formed on the surface of the reflecting plate 28 by the semiconductor technology, the light receiving surface is inclined with respect to the lens center axis C of the transmitting / receiving lens 35 due to the arrangement relationship of each part, and the reflecting plate The direction is changed by the rotation of 28, but if the change is within a predetermined range, the change in the light receiving sensitivity with respect to the change in the direction of the light receiving surface can be almost ignored. When the change in the direction of the light receiving surface is large, the signal processing unit 42 described later obtains a relationship between the direction and sensitivity in advance and corrects the light reception output for each angle based on the relationship. .

  The parallel light reflected by the reflecting portion 28 a of the rotating mirror 25 enters the transmission / reception lens 35. The transmission / reception lens 35 is a lens having a so-called convex property (the outer shape may be either a convex shape or a planar shape), and the position of the focal point F is the same as the center position of the surface of the reflecting plate 28 of the rotating mirror 25. In addition, the lens center axis C is supported by a support (not shown) in a state where the lens center axis C is parallel to the upper surface of the base 21 and is fixed upright on the base 21, and is reflected by the reflecting portion 28 a of the rotating mirror 25. The parallel light thus made is transmitted to an external space to be transmitted / received as transmission light T having an optical axis substantially parallel to the lens central axis C.

  Further, the transmission / reception lens 35 condenses the return light R from the external transmission / reception target space at the focal point and the vicinity thereof, and slightly from the focal position F at the center of the surface of the reflecting plate 28 of the rotating mirror 25 as described above. It is incident on the light receiving element 40 formed at a position away from the light receiving element.

  The semiconductor laser 22 is configured so that the light reflected by the reflecting portion 28a passes through the optical axis substantially coincident with the lens central axis C of the transmission / reception lens 35 in a state where the rotational drive of the rotational mirror 25 is stopped. Assume that the collimating lens 23 and the rotating mirror 25 are disposed.

  As shown in FIG. 2, a counter mass 45 that balances the rotational moment generated by the light receiving element 40 is fixed to the other surface of the reflecting plate 28 of the rotating mirror 25. The axial deviation of the rotation of the plate 28 is prevented.

  A mask 50 for preventing the light emitted from the collimator lens 23 through the isolator 24 from entering the light receiving element 40 is supported on the table 21c between the collimator lens 23 and the rotating mirror 25. Is provided.

  The optical transmission / reception apparatus 20 having the optical system configured as described above is portable, for example, as shown in FIG. 4. The optical transmission / reception apparatus 20 emits transmission light T from the transmission / reception lens 35 to the external space, and transmits / receives the transmission / reception lens 35 from the external space. The housing 100 has a gun shape that allows the return light R to be incident thereon, and is configured to be able to activate a light transmission / reception operation by operating an operation unit (not shown).

  Further, inside the apparatus, as shown in FIG. 5, an A / D converter 41 for A / D converting the output signal of the light receiving element 40, and a substance to be measured in the transmission / reception space based on the output of the A / D converter 41 A signal processing unit 42 that performs an evaluation process on the presence or concentration of the light and a display 43 that displays a processing result or the like are provided. Further, a mirror driving device 44 for electrostatically driving or electromagnetically driving the rotating mirror 25 is provided. The mirror driving device 44 drives the rotating mirror 25 based on scanning information designated by the signal processing unit 42.

  Although this signal processing is not described in detail, the simplest process is to compare the desired threshold value with the received light output, and display an alarm when the received light output is lower than the threshold value during the sweep. Notify that the target substance exists or the concentration is higher than the specified level.

  It is also possible to store the received light output during sweeping, perform averaging processing for each sweep, and display the spatial distribution on the display 43. From this distribution, the space where the measurement target substance is concentrated is specified. Can be easily done.

  In the optical transceiver 20 configured as described above, the light emitted from the semiconductor laser 22 and converted into parallel light by the collimator lens 23 is incident on the reflecting portion 28 a of the rotating mirror 25.

  The angle at which the light emitted from the collimator lens 23 is reflected changes as the reflecting plate 28 of the rotating mirror 25 rotates. However, since the incident position is in the vicinity of the focal point F of the transmitting / receiving lens 35, the light is emitted from the reflecting portion 28a. The transmitted light T transmitted through the transmission / reception lens 35 is emitted into the external space as a beam substantially parallel to the lens central axis C of the transmission / reception lens 35.

  The transmitted light T propagates through the space, the light component having a frequency corresponding to the absorption peak of the substance contained therein is absorbed, and further travels to the reflection / scattering body, where a part of the reflected / scattered light returns. The light R returns to the transmission / reception lens 35, is condensed at the focal point F and in the vicinity thereof, and is incident on the light receiving element 43.

  Therefore, if the wavelength of the light emitted from the semiconductor laser 22 is matched with the absorption peak of the substance to be measured, for example, the transmission / reception target space is determined from the ratio of the power of the emitted light and the power of the return light received by the light receiving element 40. It is possible to know the concentration of the target substance present in

  In addition, as described in Patent Document 1, the light emitted from the semiconductor laser 22 is subjected to frequency modulation (a variable wavelength light source), and this light is passed through a space where the measurement target substance exists, and the transmitted light is transmitted. It is also possible to determine the absorption spectrum characteristic of the space based on the output signal when received by the light receiving element 40 and measure the gas concentration of the measurement target gas. By using this method, the concentration of the substance to be measured can be measured with higher accuracy and stability.

  When the concentration of an object to be measured is actually measured by this method, light having a frequency matching the absorption peak is absorbed, but an intensity change at a frequency twice the modulation frequency can be obtained at an intensity corresponding to the concentration. Since the ratio of the intensity change of the double frequency component and the original modulation frequency is proportional to the concentration of the measurement object, the concentration can be known.

  Further, when the substance itself contained in the external space causes reflection / scattering with respect to the transmission light T, a simpler measurement principle can be applied. When light is emitted toward the particles that are reflected / scattered, if the particle density in the space is high, the return light is large, and if the density is low, the return light is small. Therefore, if the ratio of the return light to the power of the light emitted from the light source is measured, the particle density in the space can be known.

  In this case, it is not necessary to use light including a frequency corresponding to the absorption peak of the substance as described above, it is sufficient that the light has a frequency reflected and scattered by the substance, and the light source is not limited to the semiconductor laser. , LED, ASE, SLD and the like can be selected. In this case, the isolator 24 can be omitted. In the case of using the above various light sources, if the light cannot be directly incident on the collimating lens 23 due to its size or the like, the light emitted from the light source is once coupled to one end of the optical fiber and emitted from the other end. The emitted light can be emitted to the collimating lens 23.

  Furthermore, in this case, direct modulation of the light source itself or light emitted from the light source can be modulated by an external optical switch, and the transmission light T can be emitted as an optical pulse. In this case, if the same light pulse is emitted, reflected and scattered by the substance in the space, becomes return light, and the time until it is received by the light receiving element is measured, the distance to the place where the substance exists can also be known. it can.

  In the embodiment described so far, the position of the transmission / reception lens 35 is fixed relative to the rotation mirror 25, but the distance from the rotation mirror 25 to the transmission / reception lens 35 is set as shown in FIG. By providing the movable mechanism 60 that can be varied at least in a direction shorter than the focal length, the size of the scanning space can be expanded. Although the case where the transmission / reception lens 35 is moved by the variable mechanism 60 is shown here, the semiconductor laser 22, the collimating lens 23, the isolator 24, and the rotating mirror 25 may be moved integrally with respect to the transmission / reception lens 35.

  As described above, when the distance between the rotating mirror 25 and the transmission / reception lens 35 is shortened, transmission / reception lens transmission is performed except for the parallel light that is reflected by the reflecting portion 28a and travels toward the transmission / reception lens 35 but passes through the lens central axis C. Later, since the light propagates in a direction away from the lens central axis C without being parallel to the lens central axis C, the scanning space is expanded. However, since the amount of light returning to the light receiving element 40 due to reflection is reduced and defocusing occurs during reception, the S / N ratio is deteriorated and the measurement accuracy is lowered. However, since the scanning space is widened, the measurement is performed. The detection probability of the object is increased.

  Therefore, the measurement is first performed in the above-described wide-range scanning mode, and after the detection of the measurement object or after the region where the existence of the measurement object is predicted is specified, the scanning space is returned to the original to perform a high-precision measurement. You can also.

  In particular, in order to detect leaks from pipes etc., it is top priority to first detect the location of the leaking substance. Once the leaking substance is caught, the scanning space can be returned to the original state, or scanning can be performed. It is only necessary to stop and stop the rotation of the rotating mirror 25 and perform highly accurate concentration measurement. When the rotation of the rotating mirror 25 is stopped, the semiconductor laser 22, the collimating lens 23, and the rotating mirror 25 are arranged so that parallel light passes through the center of the transmission / reception lens 35 when the rotation is stopped. It is good to keep.

  The wide-range scanning mode is not limited to the method in which the lens is moved by the movable mechanism 60, but is configured so that the concave lens can be attached / detached in front of the fixed transmission / reception lens 35. A rough measurement may be performed by spreading the lens, and then the concave lens may be removed to perform an accurate measurement.

Configuration diagram of an embodiment of the present invention Diagram showing an example of the structure of a rotating mirror The figure which shows the example of the optical scanning orbit by the turning mirror The figure which shows the example of a shape of the housing | casing of embodiment The figure which shows the structure for the electric signal processing of embodiment The figure which shows the example which enabled position change of the transmission / reception lens 35

Explanation of symbols

  20: Optical transceiver, 21: Base, 22: Semiconductor laser, 23 ... Collimator lens, 24 ... Isolator, 25 ... Rotating mirror, 26 ... Outer frame, 27 ... Inner frame, 28 ... ... Reflector, 28a ... Reflecting part, 29-32 ... Connecting shaft, 35 ... Transceiving lens, 40 ... Light receiving element, 41 ... A / D converter, 42 ... Signal processing part, 43 ... Display 44, mirror drive device, 45 ... counter mass, 50 ... mask, 60 ... movable mechanism

Claims (6)

A light source (22);
A collimating lens (23) for converting light emitted from the light source into parallel light;
A rotating mirror having a reflecting portion (28a) that receives and reflects the parallel light emitted from the collimating lens, and is formed so that the portion provided with the reflecting portion can be rotated within a predetermined angle range. (25) and
The focal point is located in the vicinity of the incident position of the parallel light with respect to the rotating mirror, receives the parallel light reflected by the reflecting unit and emits the parallel light to the transmission / reception target space, and returns light from the transmission / reception target space to the focus. A transmitting and receiving lens (35) for condensing in the vicinity;
The rotating mirror is fixed at a position near the focal point of the transmission / reception lens at a portion where the reflection unit is provided and is spaced from the incident position of the parallel light, and is incident from the transmission / reception target space via the transmission / reception lens. And a light receiving element (40) for receiving the returned light.   The light source is a semiconductor laser, and an isolator (24) is provided between the collimating lens and the rotating mirror in order to block the reflected light reflected by the rotating mirror and emitted in the direction of the light source. The optical transmission / reception apparatus according to claim 1, wherein: The rotating mirror is
An inner frame (27);
A reflector (28) disposed inside the inner frame and having the reflecting portion formed on one surface;
A first connecting shaft (31, 32) that is twistably deformable and that rotatably supports the reflector on the inner side of the inner frame;
The optical transmission / reception apparatus according to claim 1, wherein the light receiving element is provided on the one surface side of the reflection plate. An outer frame (26);
A second connecting shaft (29, 30) that is twistable and deformable in a direction different from the twisting direction of the first connecting shaft, and that rotatably supports the inner frame inside the outer frame; The optical transceiver according to claim 3.   The light according to claim 3 or 4, wherein a counter mass (45) that balances a rotational moment generated by the light receiving element is fixed to the other surface of the reflecting plate of the rotating mirror. Transmitter / receiver.   The mask (50) arrange | positioned so that the light radiate | emitted from the said collimating lens may not reach | attain the said light receiving element between the said collimating lens and the said rotation mirror is provided. 5. The optical transmission / reception apparatus according to any one of 5 above.

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