JP4569424B2 - Photodetection device and photodetection method - Google Patents

Description

The present invention relates to a light detection device and a light detection method capable of detecting the direction of a light emitting element and automating optical axis adjustment based on the detected direction of the light emitting element, for example, used in a light receiving and emitting module for optical wireless communication It is what is done.

  In recent years, optical wireless transmission technology using light has been proposed as a means for transmitting information signals. As such an optical wireless transmission technology, for example, a so-called “optical wireless LAN” for performing communication between a plurality of computers, a technology for transmitting video information and audio information to an AV (Audio-Visual) device, and the like have been proposed. Yes. Such optical wireless transmission is performed by transmitting and receiving a light beam modulated in accordance with digital information between devices configured by a light receiving and emitting device.

  In order to perform accurate information communication by such optical wireless transmission, it is necessary to match the optical axes between the light receiving and emitting devices, and the optical axis adjusting function in these light receiving and emitting devices is indispensable.

  Here, when the transmitted light beam of the light emitting element on the transmitting side does not have directivity, the optical axis adjustment may be performed only on the light receiving element on the receiving side, but when the light emitting element on the transmitting side has directivity. Needs to adjust the optical axis on both the transmitting and receiving sides. Further, when performing high-speed communication in the gigahertz band, it is necessary to reduce the diameter of the light beam used for communication in order to ensure the transmission SN ratio, and it is necessary to adjust the optical axis with high accuracy.

  As an optical axis adjustment mechanism for realizing such an optical axis adjustment function, as described in Patent Document 1, a light receiving / emitting element unit is supported by a biaxial drive mechanism, and the light receiving / emitting direction of the light receiving / emitting element unit is as follows. A mechanism has been proposed that can be deflected in two axial directions.

  Furthermore, in order to reduce the size of the communication system and increase the speed of the optical axis adjustment, a mirror (biaxial deflecting means) capable of controlling the deflection in the biaxial direction is used. There has been proposed a photodetection device having an angle control mechanism in which a light beam is incident on. In this photodetection device, the direction of the light emitting element on the transmitting side is searched by deflecting the mirror in two axes, and the optical axis between the light emitting element and the light receiving element is matched by controlling the angle of the mirror. Let In the search operation in the direction of the light emitting element on the transmission side in this photodetector, for example, while monitoring the amount of light received at the light receiving element on the reception side, the mirror is deflected according to preset conditions, and the amount of received light is maximized. The current mirror direction is stored, and after the mirror deflection operation, the mirror direction is set to the stored direction.

  In such a light detection device, in order to perform the optical axis control with higher accuracy, the light beam from the light emitting element on the transmission side passes through a mirror capable of controlling the deflection in the biaxial direction, and the two-dimensional optical position is controlled. The light is incident on the detection element. In this light detection device, the optical axis between the light emitting element and the light receiving element is controlled by feedback to the control of the deflection direction of the mirror based on the information on the incident position of the light beam in the two-dimensional light position detecting element. Is adjusted with high accuracy.

  In addition, when the search range and the optical axis adjustment range by the mirror capable of controlling the deflection in the biaxial direction are not sufficiently wide, the mirror and the biaxial drive mechanism are used in combination, and the entire light emitting / receiving element unit is biaxial. By deflecting in the direction, it is possible to achieve both a wide search range and high speed optical axis adjustment.

JP 2003-8515 A

  By the way, as described above, the closed loop control in the photodetecting device having the angle control mechanism using the mirror capable of deflection control and the two-dimensional optical position detecting element is performed by the light beam being incident on the two-dimensional optical position detecting element. This is possible only when the optical axis is off and the optical axis is greatly deviated and the light beam is not incident on the two-dimensional optical position detection element. Therefore, in such a light detection device, when the optical axis is greatly deviated, a search operation is first performed, and the light beam is made incident on the two-dimensional optical position detection element, and then servo-locked. It will be necessary.

  If the servo lock is released after the servo lock is performed, it is necessary to perform the search operation again so that the servo lock is performed when the optical path is restored. In this re-search operation, the search operation is performed again for the entire wide area where the search operation is possible. Once the servo lock is done, there is a high possibility that communication has already started, so if the servo lock is released due to an optical path interruption, etc., the communication that was in progress can be resumed quickly. In addition, it is necessary to promptly lock the servo when the optical path is restored.

  However, the speed (frequency) of deflecting the mirror is limited by the effect of mechanical frequency characteristics. When the mirror is deflected at high speed (high frequency), abnormal vibration occurs due to the effect of mechanical resonance. There is a possibility that an accurate search operation cannot be performed. Such problems due to frequency characteristics and resonance become more prominent when the mirror deflection angle is widened. That is, in such a light detection device, when the angle for deflecting the mirror is increased, the speed (frequency) for deflecting the mirror cannot be increased sufficiently, and the search operation cannot be performed quickly. . In particular, when the diameter of the light beam from the light emitting unit on the transmission side is small, a high-density search operation is required, and there is a problem that the time required for the search operation becomes longer.

Therefore, the present invention has been proposed in view of the above-described circumstances, and is a photodetection device having a biaxial light deflecting means such as a mirror capable of controlling the deflection of an incident light beam, and having a servo operation. Photodetection device capable of realizing reliable and quick research operation without increasing the deflection frequency in the biaxial light deflection means in the research operation performed when the incidence of the light beam is interrupted And an optical detection method .

  In the light detection device as described above, the servo lock is released after the servo lock is performed. The reason is that the light path from the light emitting element on the transmission side is blocked by an obstacle such as a person or a bird, and the light detection device. It can be considered that the optical axis shift due to the movement or rotation of the lens exceeds the servoable range by the mirror. When the optical path is blocked by an obstacle, there is a high possibility that the optical path from the light emitting element on the transmission side is not moving, and when a large optical axis shift occurs, the optical axis is shifted. There is a high possibility that an optical path from the light emitting element on the transmission side exists in the direction. Therefore, in any of these cases, performing the search operation again for the entire wide area where the search operation can be performed also performs the search operation for an area where the optical path from the light emitting element on the transmission side is unlikely to exist. It is supposed to be.

  Therefore, the cause of the servo lock being released is identified, and when it is determined that the servo lock has been removed due to a large optical axis deviation, the direction in which the optical axis deviation has occurred is identified, and the optical path from the light emitting element on the transmission side If the re-search operation is performed only for the region where there is a high possibility of the presence of the error, the re-search operation can be completed quickly and the servo lock can be performed quickly.

  That is, in order to solve the above-described problem, the photodetector according to the present invention has any one of the following configurations.

[Configuration 1]
Biaxial light deflecting means for deflecting and emitting a light beam incident from the outside in the biaxial direction, search control means for generating a search control signal and controlling the biaxial light deflecting means based on the search control signal, servo Servo control means that generates a control signal and controls the biaxial light deflection means based on the servo control signal, and a light beam that has passed through the biaxial light deflection means is incident, and the incident position of the light beam is detected two-dimensionally. A two-dimensional light position detecting means capable of storing the change amount of the servo control signal, and the search control means when the detected light amount in the two-dimensional light position detecting means is smaller than a preset threshold value. A search operation is performed by deflection of the biaxial light deflecting means, and after detecting the incident direction of the light beam from the outside based on the incident position of the light beam detected by the two-dimensional light position detecting means, The control means controls the biaxial light deflection means to servo-control the optical axis in the incident direction, and when the incident light beam is interrupted during the servo control, the search control means automatically performs a re-search operation. The search control means generates two periodic signals having different frequencies as a search control signal when the incident light beam is interrupted, and the locus of the incident position is Lissajous by the two periodic signals. The deflection of the biaxial light deflection means is controlled independently for each axis so as to form a figure, and this change amount is determined based on the change amount of the servo control signal in the servo control immediately before the interruption stored by the storage means . when greater than value, the deflection of the two-axis beam deflecting means performs the first re-search operation for controlling to perform the region capable of it, the variation amount is higher than a predetermined value When Sai limits the amplitude of the search control signal, the deflection of the two-axis beam deflecting means characterized in that performing a second re-search operation for controlling to perform the partial region capable of it is there.

In this photodetection device, when the light beam is blocked, the search control means uses two periodic signals having different frequencies as the search control signal based on the amount of change in the servo control signal in the servo control immediately before the blocking. In the servo control immediately before the interruption stored by the storage means, the deflection of the biaxial light deflection means is independently controlled for each axis so that the locus of the incident position becomes a Lissajous figure by the two periodic signals . based on the amount of change in the servo control signal, when the amount of change is larger than a predetermined value, performs the first re-search operation for controlling to perform the region capable it deflection in two-axis light deflecting means, the when the amount of change is smaller than a predetermined value, limits the amplitude of the search control signal, the deflection of the two-axis beam deflecting means to perform some of the possible it area Since the second re-search operation to be controlled is performed , for example, an operation corresponding to whether the light beam is blocked by an optical axis shift or by an obstacle can be performed. An area where there is a high possibility that an optical path exists can be identified.
In this photodetection device, the search control means uses a Lissajous figure as the locus of the incident position in the two-dimensional light position detection means of the light beam that has passed through the biaxial light deflection means, and the light beam in the two-dimensional light position detection means. In detecting the direction of the light emitting element that causes the light beam to enter the biaxial light deflecting means by detecting the incident position, in the first re-search operation, for example, when the light beam is blocked by the optical axis shift. As a corresponding operation, control is performed so that the deflection in the biaxial light deflecting means is performed in an area in which the deflection is possible. In the second re-search operation, for example, an operation corresponding to the case where the light beam is blocked by an obstacle As a result, the direction of the light emitting element is re-established reliably and quickly because the deflection in the biaxial light deflecting means is controlled so as to be performed on a part of the region where this is possible. It can be out.

  Here, a Lissajous figure (bowditch curve) means that particles moving on a plane perform harmonic motion in two orthogonal axes, and the ratio of their frequencies is a rational number (the quotient of two integers). This is a figure drawn by the particle. In the present invention, the Lissajous figure includes a case where the ratio of the frequencies in two orthogonal axial directions is an irrational number.

[Configuration 2]
The photodetecting device having the configuration 1 includes a biaxial driving mechanism for deflecting a base supporting the biaxial light deflecting means and the two-dimensional optical position detecting means in the biaxial direction, and the search control means includes a first re-search. In operation, the direction of the optical axis deviation is determined based on the polarity of the change amount of the servo control signal in the servo control immediately before the interruption stored by the storage means, and the two-axis drive is performed in the direction corresponding to the direction of the optical axis deviation. The mechanism is controlled .

  In this photodetection device, the search control means determines the direction of the optical axis deviation as an operation corresponding to the case where the incidence of the light beam is blocked by the optical axis deviation in the first re-search operation, and It is possible to specify a region where there is a high possibility that an optical path from the light emitting element exists.

  Further, in this photodetection device, the search control means performs an operation corresponding to the case where the incidence of the light beam is interrupted due to the optical axis shift in the first re-search operation according to the direction of the optical axis shift. Since the shaft drive mechanism is controlled, the direction of the light emitting element can be reliably and rapidly detected over a wider range than when only the biaxial light deflecting means is used.

  The light detection method according to the present invention has the following configuration.
[Configuration 3]
  A two-axis light deflecting means for deflecting a light beam incident from the outside controlled by the servo control means in a biaxial direction and a light beam having passed through the two-axis light deflecting means are incident, and the incident position of the light beam is two-dimensionally determined. The amount of light detected by the two-dimensional light position detection means is smaller than a preset threshold value using a two-dimensional light position detection means that can be detected automatically and a storage means that stores the change amount of the servo control signal Then, a search operation by deflection of the biaxial light deflecting means is executed, and the incident direction of the light beam from the outside is detected based on the incident position of the light beam detected by the two-dimensional light position detecting means, and then the servo control means 2 A light detection method for controlling the optical axis deflection means to servo-control the optical axis in the incident direction, and performing a re-search operation when the incidence of the light beam is interrupted during the servo control. When the beam is interrupted, the deflection of the biaxial light deflecting means is independently controlled for each axis so that the locus of the incident position becomes a Lissajous figure by two periodic signals having different frequencies. Based on the stored change amount of the servo control signal in the servo control immediately before the interruption, when the change amount is larger than a predetermined value, the first control is performed so that the deflection in the biaxial light deflecting means is performed in an area where the change is possible. When the amount of change is smaller than a predetermined value, a second re-search operation is performed to control so that the deflection in the biaxial light deflecting means is performed on a part of the region where the change is possible. It is what.

[Configuration 4]
  In the light detection method having configuration 3, in the first re-search operation, a memory is stored in the first re-search operation using a biaxial drive mechanism that deflects the base supporting the biaxial light deflecting unit and the two-dimensional optical position detecting unit in the biaxial direction. The direction of the optical axis deviation is determined based on the polarity of the change amount of the servo control signal in the servo control immediately before the interruption stored by the means, and the biaxial drive mechanism is controlled in the direction corresponding to the direction of the optical axis deviation. It is characterized by this.

In the light detection device and the light detection method according to the present invention, when the light beam is interrupted, the search control means includes a first different from each other based on the amount of change in the servo control signal in the servo control immediately before the interruption. Since either the re-search operation or the second re-search operation is executed, for example, it is possible to perform an operation corresponding to whether the light beam is blocked by an optical axis shift or by an obstacle. It is possible to identify a region where there is a high possibility that an optical path from the side light emitting element exists.

Further, in this photodetection device and photodetection method , the search control means uses the Lissajous figure as the locus of the incident position in the two-dimensional optical position detection means of the light beam that has passed through the biaxial optical deflection means, and the two-dimensional optical position detection means. In detecting the direction of the light emitting element that causes the light beam to be incident on the biaxial light deflecting means by detecting the incident position of the light beam in the first re-search operation, for example, in the first re-search operation, the light beam is blocked. As an operation corresponding to the case of the deviation, control is performed so that the deflection in the biaxial light deflecting unit is performed in an area where the deflection is possible. In the second re-search operation, for example, when the light beam is blocked by an obstacle Is controlled so that the deflection in the biaxial light deflecting means is performed on a part of the region where it is possible to ensure the direction of the light emitting element, One can quickly re-detected.

In this photodetection device and photodetection method , the search control means, in the first re-search operation, performs an optical axis deviation direction as an operation corresponding to the case where the incidence of the light beam is blocked by the optical axis deviation. Thus, it is possible to identify an area where there is a high possibility that an optical path from the light emitting element on the transmission side exists. Further, in this photodetection device, the search control means performs an operation corresponding to the case where the incidence of the light beam is interrupted due to the optical axis deviation in the first re-search operation, depending on the direction of the optical axis deviation. Since the shaft drive mechanism is controlled, the direction of the light emitting element can be reliably and rapidly detected over a wider range than when only the biaxial light deflecting means is used.

That is, the present invention is a light detection device having a biaxial light deflecting means such as a mirror capable of controlling the deflection of an incident light beam, and is performed when the light beam is blocked during the servo operation. In the search operation, it is possible to provide a photodetection device and a photodetection method that can realize a reliable and quick re-search operation without increasing the deflection frequency in the biaxial optical deflection means.

  Embodiments of the present invention will be described below with reference to the drawings.

  The light detection device according to the present invention is used, for example, in a light receiving and emitting module for optical wireless communication, detects the direction of the light emitting element, in other words, the incident direction of the light beam, and emits the optical axis of the light receiving element. This is a light detection device for always following the optical axis of the element.

[Configuration of First Embodiment]
(Configuration of photodetection device)
FIG. 1 is a block diagram showing the configuration of the photodetection device according to the first embodiment of the present invention.

  As shown in FIG. 1, the light detection apparatus according to the present invention includes a biaxial deflection mirror 1 that is a biaxial light deflecting means capable of deflecting an incident received light beam 11 in a biaxial direction and emitting it. A light receiving beam 11 reflected by the axial deflection mirror 1 is incident, and an optical position detecting element 2 which is a two-dimensional light position detecting means capable of two-dimensionally detecting the incident position of the light receiving beam 11 is provided. Yes.

  The received light beam 11 from the light emitting element of the counterpart light emitting / receiving module incident on the light detection device is incident on the biaxial deflection mirror 1. The light receiving beam 11 incident on the biaxial deflecting mirror 1 is reflected and deflected by the biaxial deflecting mirror 1, passes through the light transmitting / receiving lens 7, and is deflected by the first beam splitter 3 and the second beam splitter 4, respectively. Then, the light passes through the condenser lens 9 and enters the light receiving surface of the optical position detecting element 2. The condensing lens 9 condenses the received light beam on the light receiving surface of the optical position detecting element 2.

  A part of the received light beam 11 incident on the second beam splitter 4 passes through the second beam splitter 4, passes through the condenser lens 10, and is received by the light receiving element 6. The light receiving element 6 receives the received light beam 11 and outputs a detection signal corresponding to the intensity of the received light beam 11. Based on this detection signal, it is possible to demodulate the reception data sent from the counterpart light emitting / receiving module.

  The photodetecting device includes an LD (Laser Diode) light emitting element 5 for signal transmission. The LD light emitting element 5 emits a transmission light beam 12 that is optically modulated in accordance with transmission data. The transmission light beam 12 emitted from the LD light emitting element 5 is converted into a parallel light beam by passing through the collimator lens 8, passes through the first beam splitter 3, and enters the biaxial deflection mirror 1. The transmitted light beam 12 incident on the biaxial deflecting mirror 1 is reflected by the biaxial deflecting mirror 1 and emitted toward a counterpart light emitting / receiving module having a light emitting element that emits a light receiving beam 11.

  The optical system of this light detection apparatus is adjusted so that the transmission light beam 12 and the light reception beam 11 are coaxial in a state where the light reception beam 11 is incident on the center of the light receiving surface of the optical position detection element 2. That is, in this optical system, the center of the light receiving surface of the optical position detecting element 2 and the light emitting point of the LD light emitting element 5 are conjugate with respect to the reflecting surfaces of the first and second beam splitters 3 and 4. Yes. Thus, in the state where the transmission light beam 12 and the light reception beam 11 are coaxial, the transmission light beam 12 can be accurately incident on the light receiving element for signal reception of the other light receiving and emitting module. it can.

  Therefore, in this photodetection device, the biaxial deflection mirror 1 is controlled so that the received light beam 11 is incident on the center of the light receiving surface of the optical position detecting element 2, thereby correcting the optical axis deviation of the transmitted / received light. Can do.

  FIG. 2 is a plan view (A), a sectional view (B), and a side view (C) showing the configuration of the biaxial deflection mirror 1.

  As shown in FIG. 2A, the biaxial deflection mirror 1 has a mirror 1a. On the back surface of the mirror 1a, four magnets 1b are fixed at symmetrical positions with respect to the center of the mirror 1a. As shown in FIG. 2B, the mirror 1a is supported at its center by a pivot 1d fixed on a base 1e. And each magnet 1b fixed to the mirror 1a is located in the magnetic path space of the four coils 1c fixed on the base 1e.

  Each magnet 1b and each coil 1c in a symmetrical position with respect to the center of the mirror 1a are attracted in one direction by supplying a predetermined drive current to the coil 1c as shown in FIG. And repel each other. By arranging the magnets 1b and the coils 1c having such a relationship on the orthogonal axes, the mirror 1a is driven in the biaxial direction with the central portion of the mirror 1a (the tip of the pivot 1d) as a fulcrum. Is done.

  FIG. 3 is a front view showing the configuration of the optical position detection element 2.

  In this optical detection device, the optical position detection element 2 to which the light beam having passed through the biaxial deflecting mirror 1 is incident, for example, as shown in FIG. This is a 4-division PD (Photo Diode) that can detect the position two-dimensionally.

  FIG. 3 shows a state in which the light receiving beam spot 2o is incident on the four light receiving surfaces 2a, 2b, 2c and 2d of the optical position detecting element 2. The optical position detection element 2 outputs four independent detection signals corresponding to the amounts of incident light on the light receiving surfaces 2a, 2b, 2c, and 2d. By comparing the detection signals from these four light receiving surfaces 2a, 2b, 2c, and 2d, the incident position of the light receiving beam spot 2o can be obtained.

  The two-dimensional light position detection means is not limited to the four-divided PD, but can be replaced with a two-dimensional PSD (Position Sensitive Detector) element, a C-MOSS sensor, or the like. In these cases, a signal similar to that obtained when the quadrant PD is used can be generated.

  In this photodetection device, the biaxial deflection mirror 1 is controlled by a DSP (Digital Signal Processor) 13 serving as search control means and servo control means for controlling the biaxial deflection mirror 1 as shown in FIG. The DSP 13 is a processor capable of performing arithmetic operation processing for discrete-time signal processing at a high speed during a fixed sampling period, and includes a plurality of operation processing units 13a, 13b, 13c and a memory 13d. Yes. In the DSP 13, the output from the servo signal calculation unit 13b is sent to the switching unit 13e and the servo amount detection calculation unit 13a. The output from the servo amount detection calculation unit 13a is sent to and stored in the memory 13d. The read signal from the memory 13d is sent to the search signal calculation unit 13c. The output from the search signal calculation unit 13c is sent to the switching unit 13e.

  Four outputs from the optical position detection element 2 are input to the DSP 13 via the A / D converter 14 to the servo signal calculation unit 13b and the switching unit 13e. The output from the DSP 13 is output from the switch 13e and sent to the mirror driver 16 via the D / A converter 15. The mirror driver 16 supplies a drive current to each coil 1c of the biaxial deflecting mirror 1 based on the signal sent from the DSP 13, and drives the biaxial deflecting mirror 1. The mirror 1a of the biaxial deflection mirror 1 is tilted in the X-axis direction and the Y-axis direction according to the drive current supplied to each coil 1c.

  The DSP 13 outputs a search control signal to the biaxial deflection mirror 1 when the search operation is executed and a servo control signal when the servo control is executed.

  In FIG. 1, in order to explain the functions of the DSP 13 in the present invention, the inside of the DSP 13 is represented by functional blocks. The memory 13d is a memory function, and the other blocks are functions executed by a program. The arrows in the DSP 13 in FIG. 1 indicate the flow of data in the DSP 13.

  The search signal calculation unit 13c executes a program routine for generating a periodic signal such as a sine wave (sine wave) to force the biaxial deflection mirror 1 to perform a biaxial deflection operation as a search control signal. To do. The search signal calculation unit 13c can receive the DC component data stored in the memory 13d and superimpose the DC component on the search control signal.

  The search control signal can cause the biaxial deflecting mirror 1 to perform a two-dimensional scanning operation by performing a raster scanning operation like electron beam scanning in a television apparatus. Further, as described in Japanese Patent Application Laid-Open No. 2005-64898, biaxial deflection is provided by providing two periodic signals having different frequencies for the X axis and Y axis of the biaxial deflection mirror 1 as a search control signal. The tilt direction of the mirror 1a of the mirror 1 changes in the direction of drawing a Lissajous figure (Bowditch curve). That is, the locus of the incident position in the optical position detecting element 2 of the light beam incident on the biaxial deflecting mirror 1 and reflected by the mirror 1a of the biaxial deflecting mirror 1 is a Lissajous figure. In this case, a high-density and high-speed search operation can be realized even with a relatively low periodic signal.

  Here, a Lissajous figure is a particle that moves on a plane that performs harmonic motion in two orthogonal axial directions, and the ratio of its frequencies is a rational number (a number that can be expressed by the quotient of two integers). Sometimes a figure drawn by the particles.

  The servo signal calculation unit 13b is configured by a servo processing program routine based on a phase compensation filter calculation for the dynamic characteristics of the biaxial deflection mirror 1. As shown in FIG. 1, the servo signal calculation unit 13b generates X-axis and Y-axis servo control signals (Sx, Sy) based on the received beam spot position information from the optical position detection element 2. Closed loop control of the biaxial deflection mirror 1 can be performed. Thereby, the incident position of the optical beam 11 with respect to the optical position detection element 2 can be set as the coordinate center in the optical position detection element 2. Thereby, it is possible to correct the optical axis deviation of the light receiving beam 11 and the transmission light beam 12.

  The switching unit 13e determines switching to whether the output of the DSP 13 is for search or for servo based on the light reception level that is the sum of the output levels of the four light receiving surfaces of the optical position detection element 2. As a result, the DSP 13 can output a search control signal to the biaxial deflecting mirror during search control, and can output a servo control signal during servo control.

  FIG. 4 is a graph showing how the servo control signal is sampled in this photodetection device.

  In the DSP 13, as shown in FIG. 4, the servo amount detection calculation unit 13a samples the servo control signal output from the servo signal calculation unit 13b at a constant period, and the latest sampling data (Sx, Sy) The average DC component (SAx, SAy) of the servo control signal is calculated by averaging calculation processing (moving average processing) with data of a predetermined number of samples before the data.

  In addition, the servo amount detection calculation unit 13a performs a difference calculation between the average DC component (SAx, SAy) of the servo control signal and the latest sampling data (Sx, Sy), thereby changing the amount of variation (SDx) of the servo control signal. , SDy).

  The servo control signal sampling data, the servo control signal fluctuation amount, and the data indicating the average DC component obtained by the servo amount detection calculation unit 13a are stored in the memory 13d while being periodically updated.

[Operation in the First Embodiment]
Hereinafter, the operation of the photodetecting device will be described.

(Search / servo switching operation)
In this photodetection device, as shown in FIG. 1, the biaxial deflection mirror 1 is controlled so that the light receiving beam 11 from the other light receiving and emitting module is incident on the coordinate center of the light receiving surface of the optical position detecting element 2. In this state, the optical axis of the transmission light beam 12 and the optical axis of the light reception beam 11 coincide with each other, and stable signal transmission is possible.

  If the light receiving beam 11 is incident on the light receiving area of the light receiving surface of the optical position detecting element 2, the servo control operation by the DSP 13 causes the light receiving beam 11 to be incident on the coordinate center of the light receiving surface. The deflection mirror 1 is controlled, and the optical axis adjustment is continued while correcting the optical axis deviation due to minute vibrations.

  However, when communication is started for the first time after installing this photodetection device, or when the relative position (angle) with the counterpart light emitting / receiving module is changed or the optical path is blocked by an obstacle, the light of the light receiving beam 11 Since the axis and the optical axis of the transmission light beam 12 are greatly deviated, the light receiving beam 11 does not enter the light receiving surface of the optical position detecting element 2, so that the optical axis cannot be adjusted by the operation of the DSP 13.

  In this photodetection device, when the optical axis of the transmission light beam 12 and the optical axis of the light reception beam 11 are greatly deviated as described above, the biaxial deflection mirror 1 is widened by the search control operation by the DSP 13. A search operation for detecting the incident direction of the received light beam 11 is performed by scanning within an angular range.

  FIG. 5 is a graph showing a Lissajous locus drawn in one second when the frequency for the X axis is 50 [Hz] and the frequency for the Y axis is 59 [Hz] in the biaxial deflection mirror.

  At the time of the search operation in this photodetection device, as shown in FIG. 5, the search control signal supplied to the biaxial deflection mirror 1 is a sine wave signal having a different frequency for the X axis control and the Y axis control. The locus of the incident position of the light beam reflected by the mirror 1a of the biaxial deflecting mirror 1 on the optical position detecting element 2 draws a Lissajous figure.

  As described above, the optical system of the light detection device is adjusted so that the transmission light beam 12 and the light reception beam 11 are coaxial when the light reception beam 11 is incident on the center of the light reception surface of the optical position detection element 2. Therefore, a Lissajous figure is also drawn in the transmission direction of the transmission light beam 12.

  When the transmission direction of the transmission light beam 12 and the optical axis of the light reception beam 11 approach during the search operation, the light reception beam 11 enters the light reception area of the light reception surface of the optical position detection element 2. At this time, the optical axis is adjusted by switching from the search operation to the servo operation (closed loop control operation), and the search operation ends.

  When the light receiving level (PL), which is the sum of the output levels from the four light receiving surfaces of the light position detecting element 2, becomes equal to or higher than a specified servo threshold (SL), the switching unit 13e performs a servo operation (closed loop control). Switch to operation) so that the optical axis is adjusted.

  During the servo operation, the optical axis is adjusted by following the direction of the light receiving beam 11 by the biaxial deflection mirror 1 as long as the light receiving beam is incident on the light receiving area of the light receiving surface of the optical position detecting element 2. .

  However, when the sum of the output levels of the four light receiving surfaces of the optical position detection element 2 is less than the prescribed servo threshold due to relative position (angle) fluctuations between the light emitting and receiving modules and an optical path interruption due to some obstacle, After determining that servo control is impossible and stopping servo control, another search operation (re-search operation) is performed.

(Detection method of servo control stop cause)
In this light detection device, during servo control, the servo control signal of the biaxial deflecting mirror 1 changes according to the change in the relative position (angle) between the light receiving and emitting modules, so that the change in the servo control signal is detected. Thus, it is possible to detect the presence or absence of relative position fluctuation between the light emitting and receiving modules.

  FIG. 7 is a flowchart illustrating a method for detecting a change in the servo control signal. This flowchart shows the operation during optical axis correction, that is, during servo control.

  In S1, the search operation is switched to the servo operation, servo control is started, and the process proceeds to S2.

  In S2, the light receiving level (PL) which is the sum of the output levels of the four light receiving surfaces of the light position detecting element 2 is sampled, and the process proceeds to S3.

  In S3, the light reception level (PL) is compared with the servo threshold value (SL). If the light reception level (PL) is larger than the servo threshold value (SL), the process proceeds to S4. Then, the process proceeds to the search routine of S7. In this search routine, the above-described search operation is executed.

  In the light reception level (PL) sampling, as indicated by (C) in FIG. 4, for example, at the time of sampling at time tb, the light reception level (PL) is recognized as being equal to or less than the servo threshold (SL).

  In S4, the X-axis and Y-axis servo control signals from the servo signal calculation unit 13b are sampled, and the process proceeds to S5. This sampling and calculation processing is performed for the X-axis and Y-axis servo control signals of the biaxial deflecting mirror 1, respectively. The servo control signal is sampled at predetermined sampling periods as shown in (A) and (B) of FIG.

  In S5, a moving average based on the sampled servo control signal and past sampling data stored in the memory 13d is obtained, the average DC component (SA) data stored in the memory 13d is updated, and the process proceeds to S6. That is, here, the average DC component (SA) of the servo control signal is updated and stored in the memory 13d until the servo control is interrupted.

  The average DC component (SAx, SAy) of the servo control signal represents the DC component of the servo control signal by optimizing the sampling interval.

  In S6, the difference (SDx, SDy) between the sampled servo control signal (Sx, Sy) and the average DC component (SAx, SAy) is obtained, and the difference (sDx, sDy) data stored in the memory 13d is updated. Then, the process returns to S2. In other words, here, the difference between the latest sampling data and the average value of the servo control signal is updated and stored in the memory 13d until the servo control is interrupted.

  When relative position fluctuations occur between the light receiving and emitting modules, the sampled servo control signals (Sx, Sy) fluctuate greatly as shown in (A) of FIG. At this time, the light receiving level (PL) in the optical position detecting element 2 is recognized as being equal to or less than the servo threshold (SL) at time tb as shown in (C) of FIG. As described above, the difference between the servo control signal (Sx, Sy) and the average DC component (SAx, SAy) at the sampling time ta immediately before the time tb when the light receiving level (PL) is equal to or less than the servo threshold (SL) ( When SDx, SDy) is larger than the predetermined threshold value (ML), it can be determined that the relative position (angle) between the light emitting and receiving modules has changed.

  When shielding occurs between the light receiving and emitting modules, the sampled servo control signals (Sx, Sy) hardly change as shown in (B) of FIG. At this time, the light receiving level (PL) in the optical position detecting element 2 is recognized as being equal to or less than the servo threshold (SL) at time tb as shown in (C) of FIG. As described above, the difference between the servo control signal (Sx, Sy) and the average DC component (SAx, SAy) at the sampling time ta immediately before the time tb when the light receiving level (PL) is equal to or less than the servo threshold (SL) ( When SDx, SDy) is smaller than a predetermined threshold (ML), it can be determined that shielding has occurred between the light receiving and emitting modules.

(Selecting the optimal search method)
FIG. 8 is a flowchart for explaining the re-search operation in the present embodiment.

  In S7 of FIG. 7 described above, the process proceeds to the search routine shown in FIG. 8, and either the first re-search operation or the second re-search operation that is different from each other is performed depending on the difference (SD).

  In S1, the search operation is started, and the process proceeds to S2. In S2, if the difference (SDx, SDy) data in the memory 13d is larger than a predetermined threshold value (ML), it is determined that the optical axis is blocked due to a relative position (angle) variation between the light receiving and emitting modules. Proceeding to S7, the first re-search operation, which is a wide-range search operation, is started, and then proceeding to S8. If the difference (SDx, SDy) data in the memory 13d is smaller than the predetermined threshold value (ML), it is determined that the optical path is blocked by temporary obstruction between the light emitting and receiving modules, and the process proceeds to S3. Then, a second re-search operation that is a search operation for a specific minute region is started.

  In S3, since it is recognized that there is no (small) relative position (angle) variation between the light emitting and receiving modules, the search control signal amplitude is limited, the search range is narrowed, and high speed and high resolution 2 starts the re-search operation and proceeds to S4.

  Since the biaxial deflecting mirror 1 has vibration characteristics caused by mass, panel constant, etc., it is difficult to drive large amplitude and high frequency, but if the search range is narrowed, the driving angle of the biaxial deflecting mirror 1 is small. Therefore, stable operation is possible even if the frequency of the drive signal is increased.

  In the first re-search operation, which is a wide-range search operation shown in FIG. 5, due to the influence of the mechanical characteristics of the biaxial deflection mirror 1, for example, the frequency of each axis is set as a sine wave drive signal of 50 Hz and 59 Hz, and the Lissajous A search operation is performed using a search trajectory as a figure. In this case, the search trajectory converges with 50 sine waves and the same trajectory is drawn every second. Further, this search trajectory is a trajectory that crosses the Y axis 100 times and the X axis 118 times when the X axis and the Y axis are defined with the center of the search trajectory as the origin. At this time, the search resolution is 11800 by multiplying the number of intersections of the two.

  FIG. 6 is a graph showing a Lissajous locus drawn in one second when the frequency on the X axis is 400 [Hz] and the frequency on the Y axis is 404 [Hz].

  When performing the second re-search operation for a minute region, for example, as shown in FIG. 6, the amplitude of the biaxial deflection mirror 1 is set to 30% (search area 9%), and the frequency of each axis is set to 400 Hz. As a sine wave drive signal of 404 Hz, a search operation is performed using a search locus that becomes a Lissajous figure.

  In this case, the search trajectory converges with 100 cycles of the sine wave, and the same trajectory is drawn every 0.25 seconds. In addition, this search trajectory is a trajectory that crosses the Y axis 200 times and the X axis 202 times when the X axis and the Y axis are defined with the center of the search trajectory as the origin. At this time, since the amplitude is 30%, the search resolution can be considered to be 133320, which is approximately 3.3 times the numerical value (40400) obtained by multiplying the number of intersections of the two.

  When performing the second re-search operation for such a minute region, the search center is determined by the average DC component (SA) of the servo control signal. By superimposing the average direct current component (SA) of the servo control signal on the search control signal, the position of the light receiving beam immediately before the optical path is interrupted can be reproduced, so only the second re-search operation for the minute region is performed. Thus, there is a high possibility that the servo control can be resumed after the obstacle disappears.

  In S4, it is determined whether or not the execution time of the second re-search operation for the minute region exceeds the specified time. If the specified time has not been exceeded, the process proceeds to S5. If the specified time has been exceeded, it is determined that the relative position (angle) between the light emitting and receiving modules has changed during the second re-search operation, and the process proceeds to S7. 1 re-search operation is started.

  In S5, the light reception level (PL) which is the sum of the output levels of the four light receiving surfaces of the optical position detection element 2 is sampled, and the process proceeds to S6.

  In S6, the light reception level (PL) is compared with the servo threshold (SL). If the light reception level (PL) is larger than the servo threshold (SL), the process proceeds to S11, and if it is smaller, the process returns to S4. The second re-search operation is continued.

  In S11, the search operation is terminated, the search operation is switched to the servo operation (closed loop control operation), the process proceeds to S12, and the search routine returns to the servo control routine shown in FIG.

  On the other hand, in S7 of FIG. 8, since the difference (SD) data in the memory 13d in S2 is larger than the predetermined threshold (ML), the optical axis is blocked by the relative position (angle) variation between the light emitting and receiving modules. The first search operation in a wide range is started, and the process proceeds to S8.

  In S8, it is determined whether the execution time of the search operation for a wide range does not exceed a specified time. If the specified time has not been exceeded, the process proceeds to S9. If the specified time has been exceeded, it is determined that the search is impossible, and the process proceeds to S13.

  In S13, the search operation is stopped, the process proceeds to S14, the apparatus is stopped, and an error display is performed.

  In S9, the light reception level (PL) which is the sum of the output levels of the four light receiving surfaces of the optical position detection element 2 is sampled, and the process proceeds to S10.

  In S10, the light reception level (PL) is compared with the servo threshold (SL). If the light reception level (PL) is larger than the servo threshold (SL), the process proceeds to S11, and if it is smaller, the process returns to S8. The re-search operation of 1 is continued.

  In S11, the search operation is terminated, the search operation is switched to the servo operation (closed loop control operation), the process proceeds to S12, and the search routine returns to the servo control routine shown in FIG.

[Configuration of Second Embodiment]
FIG. 9 is a block diagram showing a configuration of a photodetection device according to the second embodiment of the present invention.

  As shown in FIG. 9, this photodetection device can also be configured to include a biaxial drive mechanism that deflects the base supporting the biaxial deflection mirror 1 and the optical position detection element 2 in the biaxial direction. .

  In other words, in the second embodiment, the photodetecting device is housed in a frame 20 serving as a base in which the biaxial deflecting mirror 1, the optical position detecting element 2, and other optical systems are configured as one casing. It is configured. The frame 20 is deflected in the biaxial direction by a biaxial drive mechanism. The biaxial drive mechanism includes a pan drive mechanism 17 that is movable in the horizontal direction and a tilt drive mechanism 18 that is movable in the vertical direction.

  Each of the pan driving mechanism 17 and the tilt driving mechanism 18 includes a motor, and is driven via a driving circuit 19 in accordance with a driving control command from the pan / tilt driving control unit 13f of the DSP 13.

  The light detection apparatus according to the second embodiment includes the pan driving mechanism 17, the tilt driving mechanism 18, the pan / tilt driving control unit 13f, and the driving circuit 19, except for the first embodiment described above. It is comprised similarly to the photon detection apparatus in the form.

[Operation in Second Embodiment]
The photodetector in the second embodiment is based on the biaxial deflection mirror 1 only by driving the entire photodetector in the first embodiment by the pan driving mechanism 17 and the tilt driving mechanism 18. A wider range of re-search operations is possible than re-search operations.

  FIG. 10 is a flowchart for explaining a re-search operation in the second embodiment.

  Also in this photodetection device, as shown in FIG. 7 described above, when the change in the servo control signal is detected and the light reception level (PL) is smaller than the prescribed servo threshold (SL) in S3 of FIG. Then, it is determined that the re-search operation is necessary, and the process proceeds to the search routine shown in FIG.

  In S1, the search operation is started, and the process proceeds to S2. In S2, if the difference (SDx, SDy) data in the memory 13d is larger than a predetermined threshold value (ML), it is determined that the optical axis is blocked due to a relative position (angle) variation between the light receiving and emitting modules. Proceeding to S7, the first re-search operation, which is a wide-range search operation, is started, and then proceeding to S8. If the difference (SDx, SDy) data in the memory 13d is smaller than the predetermined threshold value (ML), it is determined that the optical path is blocked by temporary obstruction between the light emitting and receiving modules, and the process proceeds to S3. Then, a second re-search operation that is a search operation for a specific minute region is started.

  In S3, since it is recognized that there is no (small) relative position (angle) variation between the light emitting and receiving modules, the search control signal amplitude is limited, the search range is narrowed, and high speed and high resolution 2 starts the re-search operation and proceeds to S4.

  In S4, it is determined whether or not the execution time of the second re-search operation for the minute region exceeds the specified time. If the specified time has not been exceeded, the process proceeds to S5. If the specified time has been exceeded, it is determined that a change in the relative position (angle) between the light emitting and receiving modules has occurred during the search operation, and the process proceeds to S8. 1 re-search operation is started.

  In S5, the light reception level (PL) which is the sum of the output levels of the four light receiving surfaces of the optical position detection element 2 is sampled, and the process proceeds to S6.

  In S6, the light receiving level (PL) is compared with the servo threshold (SL). If the light receiving level (PL) is larger than the servo threshold (SL), the process proceeds to S13, and if it is smaller, the process returns to S4. The second re-search operation is continued.

  In S13, the search operation is terminated, the search operation is switched to the servo operation (closed loop control operation), the process proceeds to S14, and the search routine returns to the servo control routine shown in FIG.

  On the other hand, in S7 of FIG. 10, since the difference (SD) data in the memory 13d is larger than the predetermined threshold (ML) in S2, the optical axis is blocked by the relative position (angle) variation between the light emitting and receiving modules. The first re-search operation which is a wide-range search operation is started, and the process proceeds to S8.

  Here, only the driving of the pan driving mechanism 17 and the tilt driving mechanism 18 has a low driving speed and cannot perform a search operation with high resolution. Therefore, the search operation by the biaxial deflection mirror 1 is also started simultaneously. That is, in S8, a search operation for continuously driving the pan drive mechanism 17 and the tilt drive mechanism 18 is started, and a wide-range first re-search operation is performed in combination with the search operation by the biaxial deflection mirror 1. To do.

  At this time, as shown in FIG. 4A, the pan / tilt drive control unit 13f has the magnitude and polarity of the servo control data (Sx, Sy) sampled at time ta immediately before the optical path is blocked. The pan direction position data and the tilt direction position data in the direction in which the optical axis deviates is calculated (predicted) based on, and the pan drive mechanism 17 and the tilt drive are set so that these positions become the start positions of a wide range search operation. The mechanism 18 is controlled.

  In this way, in this photodetection device, the movement direction of the optical axis deviation can be predicted, and the first re-search operation can be preferentially executed in the predicted direction.

  In S9, it is determined whether or not the execution time of the first re-search operation for a wide range exceeds a specified time. If the specified time has not been exceeded, the process proceeds to S10. If the specified time has been exceeded, it is determined that the search is impossible and the process proceeds to S15.

  In S15, the search operation is stopped, the process proceeds to S16, the apparatus is stopped, and an error display is performed.

  In S10, the light reception level (PL) which is the sum of the output levels of the four light receiving surfaces of the optical position detection element 2 is sampled, and the process proceeds to S11.

  In S11, the light receiving level (PL) is compared with the servo threshold (SL). If the light receiving level (PL) is larger than the servo threshold (SL), the process proceeds to S12, and if smaller, the process returns to S9. The re-search operation of 1 is continued.

  In S12, the driving of the pan driving mechanism 17 and the tilt driving mechanism 18 is stopped.

  In S13, the re-search operation is terminated, the search operation is switched to the servo operation (closed loop control operation), the process proceeds to S14, and the search routine returns to the servo control routine shown in FIG.

  As described above, in the light detection device according to the present invention, when the light receiving level (PL) is lowered and servo control for optical axis correction becomes impossible, the amount of change in the servo control signal immediately before that is changed. By detecting whether or not the cause is, for example, an optical axis shift due to the movement of the relative position between the light receiving and emitting modules, or whether the optical path is interrupted by a temporary obstacle. Search operations can be performed and re-search operations can be optimized.

  Further, in this photodetection device, it is possible to determine (predict) the direction of the optical axis deviation based on the moving direction of the optical axis deviation, and to perform a pre-research operation for the direction of the optical axis deviation. Rapid optical axis alignment becomes possible.

  The light detection device according to the present invention is not limited to the light emitting / receiving module as in the above-described embodiment, but also includes a sensor that detects the position (direction) of the light emitter and the light reflector, and a light emitter tracking system. It is also applicable to.

It is a block diagram which shows the structure of the photon detection apparatus which concerns on the 1st Embodiment of this invention. It is the top view (A), sectional drawing (B), and side view (C) which show the structure of the biaxial deflection | deviation mirror 1 of the said photon detection apparatus. It is a front view which shows the structure of the optical position detection element 2 of the said photon detection apparatus. It is a graph which shows the mode of the sampling of the servo control signal in the said photon detection apparatus. 6 is a graph showing a Lissajous locus drawn in one second when the frequency about the X axis is 50 [Hz] and the frequency about the Y axis is 59 [Hz] in the two-axis deflection mirror of the photodetecting device. 4 is a graph showing a Lissajous locus drawn in one second when the frequency for the X axis is 400 [Hz] and the frequency for the Y axis is 404 [Hz] in the biaxial deflecting mirror of the photodetecting device. It is a flowchart explaining the detection method of the change of the servo control signal in the biaxial deflection | deviation mirror of the said photon detection apparatus. It is a flowchart explaining the re-search operation | movement of the said photon detection apparatus. It is a block diagram which shows the structure of the photon detection apparatus which concerns on the 2nd Embodiment of this invention. It is a flowchart explaining the re-search operation | movement in the 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 2 axis | shaft deflection | deviation mirror 2 Optical position detection element 11 Light reception beam 13 DSP (Digital Signal Processor)
17 Pan drive mechanism 18 Tilt drive mechanism ML Predetermined threshold value PL detected light quantity Sx servo control signal Sy servo control signal SL threshold value

Claims (4)

A biaxial light deflecting means for deflecting and emitting a light beam incident from the outside in the biaxial direction;
Search control means for generating a search control signal and controlling the biaxial light deflection means based on the search control signal;
Servo control means for generating a servo control signal and controlling the biaxial light deflection means based on the servo control signal;
A two-dimensional light position detecting means capable of two-dimensionally detecting an incident position of the light beam incident on the light beam having passed through the two-axis light deflecting means ;
Storage means for storing a change amount of the servo control signal ,
When the amount of light detected by the two-dimensional light position detecting means is smaller than a preset threshold, the search control means executes a search operation by deflection of the two-axis light deflecting means, and the two-dimensional light position detecting means detects After detecting the incident direction of the light beam from the outside based on the incident position of the light beam, the servo control unit controls the biaxial light deflecting unit to servo-control the optical axis in the incident direction. A photodetection device that automatically performs a re-search operation by the search control means when the incidence of the light beam is interrupted during the servo control,
The search control means generates two periodic signals having different frequencies as the search control signal when the incidence of the light beam is interrupted, and the locus of the incident position becomes a Lissajous figure by the two periodic signals. The deflection of the biaxial light deflection means is independently controlled for each axis , and based on the change amount of the servo control signal in the servo control immediately before the interruption stored by the storage means , this change amount is a predetermined value. when larger, the deflection of the two-axis beam deflecting means performs the first re-search operation for controlling to perform the area available it, when the variation amount is smaller than a predetermined value, the search control limiting the amplitude of the signal, and performing a second re-search operation for controlling to perform some of the possible it regions deflection in the two-axis light deflecting means Detection device. A biaxial drive mechanism for deflecting a base supporting the biaxial light deflecting means and the two-dimensional optical position detecting means in a biaxial direction;
The search control means determines the direction of the optical axis deviation based on the polarity of the change amount of the servo control signal in the servo control immediately before the interruption stored by the storage means in the first re-search operation, The photodetection device according to claim 1 , wherein the biaxial drive mechanism is controlled in a direction corresponding to the direction of the optical axis deviation.   A biaxial light deflector that deflects and emits a light beam incident from the outside controlled by the servo control means in a biaxial direction, and a light beam that has passed through the biaxial light deflector is incident. Using a two-dimensional optical position detection means capable of detecting in a two-dimensional manner and a storage means for storing a change amount of the servo control signal,
  The light beam detected by the two-dimensional light position detecting means is executed by performing a search operation by deflection of the two-axis light deflecting means when the detected light amount in the two-dimensional light position detecting means is smaller than a preset threshold value. After detecting the incident direction of the light beam from the outside based on the incident position, the servo control means controls the biaxial light deflection means to servo-control the optical axis in the incident direction, and this servo control A light detection method for performing a re-search operation when the incident light beam is interrupted,
  When the incidence of the light beam is interrupted, the deflection of the biaxial light deflecting means is independently controlled for each axis so that the locus of the incident position becomes a Lissajous figure by two periodic signals having different frequencies. Based on the change amount of the servo control signal in the servo control immediately before the interruption stored by the storage means, when this change amount is larger than a predetermined value, the deflection in the biaxial light deflecting means can be performed. When the first re-search operation is performed to control the change, and the amount of change is smaller than a predetermined value, the second re-search is performed to control the deflection in the biaxial optical deflecting means for a part of the region where the change is possible. Perform search operation
  An optical detection method characterized by the above.   Using a biaxial drive mechanism for deflecting the base supporting the biaxial light deflecting means and the two-dimensional optical position detecting means in the biaxial direction,
  In the first re-search operation, the direction of the optical axis deviation is determined based on the polarity of the change amount of the servo control signal in the servo control immediately before the interruption stored by the storage means, and the direction of the optical axis deviation. The biaxial drive mechanism is controlled in the direction according to
  The light detection method according to claim 3.