JP2007318741A - Optical receiver and optical receiving method - Google Patents

Abstract

An optical receiver that realizes a high S / N ratio of a received signal by branching a part of an optical signal and performing optical axis detection only when the optical axis is deviated.
A condensing unit condenses an incident optical signal. The optical element 110 has a transmission region 111 and a branch region 112, and an optical signal collected by the light collecting unit 100 is incident thereon. The signal light receiving unit 120 receives the transmitted light transmitted through the transmission region 111. The detection light receiving unit 130 receives the branched light branched in the branch region 112 and performs photoelectric conversion to output a detection intensity signal indicating the intensity of the branched light. The optical axis detection unit 140 detects an optical axis shift based on the detection intensity signal output from the detection light receiving unit 130, and outputs an optical axis detection signal. The optical axis adjustment unit 150 performs optical axis adjustment based on the optical axis detection signal.
[Selection] Figure 1

Description

  The present invention relates to an optical receiver used in optical space transmission, and more specifically, a part of an optical signal is branched only when the optical axis is shifted, and optical axis detection is performed, so that S of a high received signal can be obtained. The present invention relates to an optical receiver that realizes an / N ratio and an optical reception method.

  As a data communication method in a portable information terminal such as a cellular phone or a PDA, wireless transmission that does not require wiring has become popular. In particular, wireless LANs that use 2.4 / 5.2 Hz band radio waves as a carrier wave are widely used, but contrary to their convenience, inter-channel interference and security degradation due to radio wave leakage, transmission speed limit (several tens of Mbps) There are also disadvantages.

  Therefore, optical space transmission using infrared rays having various advantages over radio waves has begun to attract attention. Advantages of using infrared rays as a carrier wave include security due to light straightness / light-shielding property, possibility of high-speed transmission utilizing the broadband property of an optical carrier wave, and the like. However, in the case of optical carrier waves, it is necessary to install the transmitters and receivers so as to face each other because of their straightness. Therefore, in the optical receiver, the flexibility of installation increases as the light receiving range is wider.

  Conventionally, as means for expanding the light receiving range of an optical receiver, an optical system that uses a high numerical aperture lens to devise an optical system to widen the light receiving range and the optical axis of the optical signal output from the optical transmitter are used. There is a mechanical type that detects and moves the optical receiver itself or adjusts the optical axis by moving a lens, a mirror, a light receiving element or the like. In the case of the latter, the light receiving angle of the optical system is not as wide as in the case of the former optical, but by adjusting the optical axis, only the optical signal near the optical axis can be received. Compared with, it was possible to reduce the influence of unnecessary light and increase the S / N of the received signal.

  Here, as a conventional optical receiver using mechanical means, for example, there is one described in Patent Document 1. FIG. 11 is a block diagram showing a configuration of a conventional optical receiver described in Patent Document 1. In FIG. In FIG. 11, a conventional optical receiver includes a total reflection mirror 900, a branch mirror 910, a signal light receiving element 920, an optical axis detecting light receiving element 930, condensing lenses 901 and 902, and an optical axis detecting circuit. A unit 940 and an optical axis adjustment unit 950.

  The optical signal that has reached the optical receiver is reflected by the total reflection mirror 900 toward the branch mirror 910, and after a part of the optical signal is reflected by the branch mirror 910 toward the condenser lens 901, The condensed light is combined with the light receiving element 930 for detecting the optical axis. The optical signal transmitted through the branch mirror 910 is collected by the condenser lens 902 and coupled to the signal light receiving element 920.

FIG. 12 is a diagram illustrating an example of a schematic configuration of a light receiving element 930 for detecting an optical axis used in a conventional optical receiver. The optical axis detecting light receiving element 930 is a light receiving element whose light receiving surface is divided into a plurality of regions 931, 932, 933, and 934 as shown in FIG. An electric signal corresponding to the ratio of the spot 935 is output. The optical axis detection circuit unit 940 detects an optical axis shift based on the electrical signal output from the optical axis detection light receiving element 930 and outputs an optical axis detection signal to the optical axis adjustment unit 950. The optical axis adjustment unit 950 adjusts the angle of the total reflection mirror 900 based on the optical axis detection signal.
JP-A-5-133716

  However, in the conventional optical receiver, a part of the received optical signal is branched by the branch mirror 910, so that even when the optical axis is not shifted, a part of the optical signal is always branched for detecting the optical axis. Therefore, there is a problem that the power of the optical signal combined with the signal light receiving element 920 is reduced, and the S / N of the received signal is deteriorated.

  Therefore, an object of the present invention is to solve the above-described conventional problems, and by dividing a part of an optical signal and performing optical axis detection only when the optical axis is shifted, an S / N of a high received signal is obtained. It is an object to provide an optical receiver and an optical reception method.

  The present invention is directed to an optical receiver that receives an optical signal transmitted to a medium through space. In order to achieve the above object, the optical receiver of the present invention has a condensing unit that condenses an incident optical signal, a transmission region, and a branch region, and is collected by the condensing unit. An optical element to which an optical signal is incident, a signal light receiving unit that receives and transmits light transmitted through the transmission region, and a branch light branched in the branch region are received and photoelectrically converted. A detection light-receiving unit that outputs a detection intensity signal indicating the intensity of the branched light, and an optical axis detection that detects an optical axis shift based on the detection intensity signal output from the detection light-receiving unit and outputs an optical axis detection signal And an optical axis adjustment unit that performs optical axis adjustment based on the optical axis detection signal. The optical element is disposed at a position between the light condensing unit and the signal light receiving unit so that the central axis of the signal light receiving unit and the central axis of the transmission region substantially coincide with each other. The branch region is a part of the optical signal, leaked light caused by the optical axis deviation is incident, and the branched light is emitted toward the detection light receiving unit.

  According to this, when an optical axis shift occurs, a part of the optical signal is used for optical axis detection, and when there is no optical axis shift, most of the optical signal collected by the light collecting unit is transmitted. Since it passes through the area and is coupled with the signal light receiving unit, it is possible to efficiently receive the optical signal.

  Preferably, the optical element has an annular boundary shape between the transmission region and the branch region, and the boundary diameter is larger than the diameter of the cross section of the light beam of the collected optical signal at the position of the optical element. . According to this, even if the optical axis is shifted in any direction with respect to the normal direction of rotation about the central axis of the transmission region, a part of the collected optical signal can be incident on the branch region. .

  In addition, the optical element has an annular boundary shape between the transmission region and the branch region, the boundary diameter is larger than the diameter of the light beam cross section of the collected optical signal at the position of the optical element, and the boundary shape However, it may be substantially similar to the light beam cross section of the collected optical signal at the position of the optical element. According to this, even if the optical axis is deviated in any direction with respect to the normal direction of rotation about the central axis of the transmission region, a part of the uniformly collected optical signal is incident on the branch region. Can do.

  Preferably, the transmission region is a hole having a diameter larger than the diameter of the light beam cross section of the collected optical signal opened in the optical element. According to this, it is possible to reduce a loss when the optical signal passes through the transmission region.

  Preferably, the detection light-receiving unit is disposed concentrically with the signal light-receiving unit. According to this, the branched light can be received regardless of which direction the optical axis is deviated from the normal direction of rotation about the central axis of the transmission region.

  Further, the detection light-receiving unit may be concentrically arranged with the signal light-receiving unit, and may have a plurality of regions for performing photoelectric conversion. According to this, branched light can be received regardless of the direction of the optical axis in any direction relative to the normal direction of rotation about the central axis of the transmission region, and the branch is received in a region where a plurality of photoelectric conversions are performed. Thus, a more detailed optical axis shift can be detected.

  The branch region has a negative focal length, and spreads the incident light toward the detection light-receiving unit. According to this, the branched light can be emitted to the plurality of light receiving regions of the detection light receiving unit.

  Preferably, the branch region is configured by a Fresnel lens or a diffractive lens. According to this, the optical element can be made thin.

  Further, the detection light-receiving unit is formed on the same substrate as the signal light-receiving unit. According to this, the light receiving part for detection and the light receiving part for signal can be integrated, and the number of parts can be reduced.

  Preferably, the optical receiver further includes a reception circuit unit that outputs a reception intensity signal indicating a reception intensity of the transmitted light based on a signal obtained by photoelectrically converting the transmitted light by the signal reception unit. In this case, the optical axis adjustment unit performs optical axis adjustment based on the optical axis detection signal and the reception intensity signal. According to this, the optical axis adjustment unit can adjust the optical axis while judging the degree of optical axis deviation.

  Preferably, the optical axis adjustment unit satisfies the first condition that the reception intensity signal is larger than the first threshold value and the optical axis detection signal is smaller than the second threshold value. And when the first condition is not satisfied, the second condition is that the reception intensity signal is larger than the first threshold value and the optical axis detection signal is larger than the second threshold value. When the second condition is satisfied, it is determined whether or not the optical axis adjustment is performed by reducing the change width of the optical axis adjustment. When the second condition is not satisfied, the reception intensity signal is the first. It is determined whether or not the third condition that the optical axis detection signal is smaller than the second threshold value and the optical axis detection signal is larger than the second threshold value is satisfied. If the optical axis is adjusted with a medium change width and the third condition is not satisfied, the change width of the optical axis adjustment is increased. Thus, the optical axis search is performed in all directions where the optical axis can be adjusted. At that time, the reception intensity signal is larger than the first threshold value, or the optical axis detection signal is larger than the second threshold value. It is determined whether or not the fourth condition of large is satisfied, and when the fourth condition is satisfied, it is determined again whether or not the first condition is satisfied, and when the fourth condition is not satisfied, the optical axis Stop adjustment.

  According to this, the optical axis adjustment unit changes the optical axis adjustment width according to the magnitudes of the reception intensity signal and the optical axis detection signal, thereby enabling more efficient optical axis adjustment. It becomes possible.

  The optical axis adjustment unit adjusts the optical axis based on the optical axis detection signal and satisfies the first condition when the first condition that the optical axis detection signal is larger than the predetermined threshold value is satisfied. If there is not, it is determined whether or not the reception intensity signal satisfies the second condition that the signal light receiving unit is larger than the minimum reception signal intensity that can be communicated without error, and when the second condition is satisfied, When the optical axis is maintained and the second condition is not satisfied, the optical axis search is performed in all directions where the optical axis can be adjusted, and the third condition that the optical axis detection signal is larger than a predetermined threshold value at that time It may be determined whether or not the third condition is satisfied, the optical axis may be adjusted based on the optical axis detection signal when the third condition is satisfied, and the optical axis adjustment may be interrupted when the third condition is not satisfied.

  According to this, the optical axis adjustment unit can detect and adjust the optical axis deviation by a simpler procedure.

  The present invention is also directed to an optical receiving method executed by an optical receiver that receives an optical signal transmitted to a medium through space. In order to achieve the above object, the method of the present invention includes a condensing step for condensing an incident optical signal, and among the collected optical signals, an optical signal that coincides with the optical axis is used as transmitted light. A step of branching an optical signal that has been transmitted and does not coincide with the optical axis as a branched light, a signal receiving step for receiving the transmitted light and performing photoelectric conversion, and a branch by receiving the branched light and performing photoelectric conversion A detection light receiving step for outputting a detection intensity signal indicating the intensity of light, an optical axis detection step for detecting an optical axis shift based on the detection intensity signal, and outputting an optical axis detection signal, and an optical axis detection signal. An optical axis adjustment step for performing optical axis adjustment.

  According to this, when an optical axis shift occurs, a part of the optical signal is used for optical axis detection, and when there is no optical axis shift, most of the optical signal collected by the light collecting unit is transmitted. Since it passes through the area and is coupled with the signal light receiving unit, it is possible to efficiently receive the optical signal.

  The present invention is also directed to an optical axis misalignment detection method executed by an optical receiver that receives an optical signal transmitted to a medium through a space. In order to achieve the above object, the optical axis misalignment detection method of the present invention includes a condensing step for condensing an incident optical signal, and an optical signal that matches the optical axis among the collected optical signals. A step of branching the leakage light that is transmitted as transmitted light and caused by optical axis misalignment as a branched light, a light receiving step for receiving the transmitted light and performing photoelectric conversion, and receiving the branched light and performing photoelectric conversion A detection light receiving step for outputting a detection intensity signal indicating the intensity of the branched light, and an optical axis detection step for detecting an optical axis shift based on the detection intensity signal and outputting an optical axis detection signal.

  According to this, when an optical axis shift occurs, a part of the optical signal is used for optical axis detection, and when there is no optical axis shift, most of the optical signal collected by the light collecting unit is transmitted. The optical axis shift can be detected while realizing a high S / N ratio of the received signal because it is coupled with the signal light receiving section through the region.

  As described above, according to the present invention, the boundary between the transmission region and the branch region of the optical element is annular, and the boundary diameter is larger than the light beam diameter of the collected optical signal at the position of the optical element. Therefore, when there is no optical axis deviation, all of the collected optical signal can pass through the transmission region and be coupled to the signal light receiving unit, and when the optical axis deviation occurs, the light is collected. Only a part of the optical signal enters the branch region, and the optical axis can be detected by the detection light receiving unit. This makes it possible to realize optical axis adjustment while reducing optical signal loss.

  These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.

Embodiments of the present invention will be described below with reference to the drawings.
(First embodiment)
1 and 2 are block diagrams showing an example of a schematic configuration of the optical receiver 1 according to the first embodiment of the present invention. FIG. 3 is a perspective view showing a schematic configuration of the optical receiver 1 according to the first embodiment of the present invention. However, FIGS. 1 and 3 show the state of the optical receiver 1 when there is no optical axis deviation, and FIG. 2 shows the state of the optical receiver 1 when the optical axis deviation occurs.

  1 to 3, the optical receiver 1 includes a condensing unit 100, an optical element 110, a signal light receiving unit 120, a detection light receiving unit 130, an optical axis detection unit 140, and an optical axis adjustment unit 150.

  The condensing unit 100 is a convex lens that receives an optical signal and emits the collected optical signal toward the optical element 110. The optical element 110 includes a transmission region 111 and a branch region 112, and the central axis of the signal light receiving unit 120 and the center of the transmission region 111 are positioned between the light collecting unit 100 and the signal light receiving unit 120. Arranged so that the axes coincide. Further, the boundary shape between the transmission region 111 and the branch region 112 is annular, and the diameter of the boundary is larger than the diameter of the light beam of the collected optical signal at the position where the optical element 110 is disposed. Further, it is desirable that the shape of the boundary is substantially similar to the light beam cross section of the collected optical signal at the position where the optical element 110 is disposed.

  FIG. 4 is a schematic diagram illustrating an example of a schematic configuration of the optical element 110. In FIG. 4, the hatched portion indicates the branch region 112. The transmission region 111 is a hole that is opened in the optical element 110 and has a diameter larger than the diameter of the light beam of the collected optical signal, and emits the collected optical signal as transmitted light.

  The branch region 112 shown in FIG. 4A is composed of a Fresnel lens, has a negative focal length, that is, a focus opposite to the incident direction of the light beam, and spreads the light flux of the incident optical signal. Exit. That is, when an optical signal collected on the branch region 112 is incident, the light beam of the incident optical signal is spread and emitted as branched light. The branch region 112 is preferably made of a material having a high refractive index with respect to the wavelength of the optical signal and a low absorption loss.

  The shape of the branch region 112 is not limited to the Fresnel lens as shown in FIG. 4A, but may be a diffractive lens or a prism shape as shown in FIG. Further, the transmissive region 111 may be made of the same material as that of the optical element 110 as shown in FIG. 4B and FIG.

  The signal light receiving unit 120 receives transmitted light and photoelectrically converts it to output an electrical signal. The detection light receiving unit 130 receives the branched light and photoelectrically converts it to output a detection intensity signal indicating the intensity of the branched light. The optical axis detection unit 140 detects an optical axis shift based on the detection intensity signal output from the detection light receiving unit 130, and outputs an optical axis detection signal. The optical axis adjustment unit 150 performs optical axis adjustment based on the optical axis detection signal output from the optical axis detection unit 140. In addition, the optical receiver shown in this embodiment has shown the structure which adjusts an optical axis by moving the condensing part 100. FIG.

  As shown in FIGS. 1 and 3, when the optical axis shift does not occur, the optical signal is collected by the light collecting unit 100, and then passes through the transmission region 111 and is coupled to the signal light receiving unit 120. At that time, the boundary between the transmission region 111 and the branch region 112 is annular, and the diameter of the boundary is larger than the diameter of the light beam section 113 of the collected optical signal at the position where the optical element 110 is disposed. Most of the collected optical signal passes through the transmission region 111 and hardly enters the branch region 112. Therefore, it is possible to significantly reduce the loss of the optical signal as compared with the conventional optical receiver that always branches a part of the received optical signal.

  On the other hand, when the optical axis shift occurs as shown in FIG. 2, after the optical signal is collected by the light collecting unit 100, a part of the light signal passes through the transmission region 111 and is coupled to the signal light receiving unit 120. A part of the leakage light enters the branch region 112. Here, the leakage light is light that is not coupled to the signal light receiving unit 120 among the collected optical signals if the optical element 110 is not provided. As shown by the broken line in FIG. 2, the leaked light incident on the branch region 112 is emitted so that the light beam spreads toward the detection light receiving unit 130.

  Here, the method in which the optical receiver 1 detects the optical axis deviation will be specifically described with reference to FIG. FIG. 5 is a schematic diagram showing a schematic configuration of the detection light receiving unit 130. In FIG. 5, the detection light-receiving unit 130 is manufactured on the same substrate as the signal light-receiving unit 120, and the photoelectric conversion regions 131 to 134 that are divided so as to have substantially the same area are the signal light-receiving unit 120. Are arranged concentrically. The detection light receiving unit 130 outputs a detection intensity signal corresponding to the ratio of the branched light received by each of the photoelectric conversion regions 131 to 134.

  5 indicate a transmitted light image 160 and a branched light image 161 in the detection light receiving unit 130, respectively. When the optical axis is shifted, the branched light image 161 is received by the plurality of photoelectric conversion regions 131 to 134 of the detection light receiving unit 130. For example, if the magnitudes of the detection intensity signals output from the photoelectric conversion area 131 and the photoelectric conversion area 133 are equal, it can be detected that the optical axis is shifted in the X-axis direction. Further, when the magnitudes of the detection intensity signals output from the photoelectric conversion area 131 and the photoelectric conversion area 133 are different, the detection intensity signals output from the photoelectric conversion area 131 and the photoelectric conversion area 133 are different. Depending on the size ratio, for example, it can be detected that the optical axis is displaced in the direction of the arrow a.

  As described above, when the optical signal is spread out at the branch region 112 and emitted, the detection light receiving unit 130 can receive the optical signal at the plurality of photoelectric conversion regions 131 to 134, so that the light beam is not expanded. It becomes possible to detect a detailed optical axis deviation direction.

  As described above, according to the optical receiver 1 according to the first embodiment of the present invention, the boundary between the transmission region 111 and the branch region 112 of the optical element 110 is annular, and the boundary diameter is the position of the optical element 110. Becomes larger than the beam diameter of the collected optical signal. Therefore, if there is no optical axis deviation, all of the collected optical signals can pass through the transmission region 111 and be coupled to the signal light receiving unit 120, and if there is an optical axis deviation, Only a part of the emitted optical signal enters the branch region 112, and the optical axis can be detected by the detection light receiving unit 130. This makes it possible to realize optical axis adjustment while reducing optical signal loss.

  The condensing unit 100 only needs to have a function of condensing incident light, and the form thereof may be a convex lens, a diffractive lens, or a concave mirror. If the lens has a higher numerical aperture, the optical system can be downsized.

  In addition, the detection light receiving unit 130 has the photoelectric conversion region divided into four parts, but the number of divisions is not limited to this, and the photoelectric conversion region is divided into a plurality of parts. Thus, it is possible to detect an accurate optical axis deviation direction.

  Further, the detection light receiving unit 130 may have a configuration in which a plurality of light receiving elements are arranged concentrically around the signal light receiving unit 120.

  Further, the optical axis adjustment unit 150 is not limited to the configuration for moving the condensing unit 100, and has a function equivalent to this, such as changing the optical axis of the optical receiver 1 by a reflection mirror or the like. If it is.

(Second Embodiment)
6 and 7 are block diagrams illustrating an example of a schematic configuration of the optical receiver 2 according to the second embodiment of the present invention. However, FIG. 6 shows the optical receiver 2 when there is no optical axis deviation, and FIG. 7 shows the optical receiver 2 when the optical axis deviation occurs. Here, the same components as those of the optical receiver 1 according to the first embodiment of the present invention are denoted by the same reference numerals, and description thereof is omitted.

  6 and 7, the optical receiver 2 further includes a receiving circuit unit 121. The reception circuit unit 121 outputs a reception intensity signal Pa based on the electrical signal photoelectrically converted by the signal light receiving unit 120. The optical axis adjustment unit 151 performs optical axis adjustment based on the reception intensity signal Pa output from the reception circuit unit 121 and the optical axis detection signal Pb output from the optical axis detection unit 140.

  Here, the operation of the optical axis adjustment unit 151 will be specifically described with reference to FIG. FIG. 8 is a flowchart illustrating an example of the operation of the optical axis adjustment unit 151. Referring to FIG. 8, in order to determine whether or not there is an optical axis shift, optical axis adjustment unit 151 has reception intensity signal Pa larger than a predetermined threshold value P1, and optical axis detection signal Pb is a predetermined value. It is determined whether or not the condition of being smaller than the threshold value P2 (that is, Pa> P1 and Pb <P2) is satisfied (step S101). When this condition is satisfied, since most of the optical signals are coupled to the signal light receiving unit 120, the optical axis adjustment unit 151 maintains the optical axis and determines the condition of step S101 again after a certain period of time. (Step S111).

  When the condition of step S101 is not satisfied, the optical axis adjustment unit 151 determines that the optical axis deviation is large, so that the reception intensity signal Pa is greater than the predetermined threshold value P1 and the optical axis detection signal Pb is predetermined. It is determined whether or not the condition (ie, Pa> P1 and Pb> P2) that is greater than the threshold value P2 is satisfied (step S102). When this condition is satisfied, since a certain amount of optical signals are coupled to the signal light receiving unit 120 and a part of the optical signals are coupled to the detection light receiving unit 130, the optical axis adjustment unit 151 has the optical axis. The optical axis adjustment is performed by reducing the adjustment change range, and after a certain period, the condition of step S101 is determined again (step S112).

  When the condition of step S102 is not satisfied, the optical axis adjustment unit 151 further determines the degree of optical axis deviation, so that the reception intensity signal Pa is smaller than the predetermined threshold value P1, and the optical axis detection signal Pb is It is determined whether or not a condition of being larger than a predetermined threshold value P2 (ie, Pa <P1 and Pb> P2) is satisfied (step S103). When this condition is satisfied, since the optical signal is not coupled to the reception light receiving unit 120 and most of the optical signals are coupled to the detection light receiving unit 130, the optical axis adjustment unit 151 performs the optical axis adjustment. The optical axis adjustment is performed with the change width of the medium being medium, and after a predetermined time, the condition of step S101 is determined again (step S113).

  If the condition of step S103 is not satisfied, the optical axis may be shifted to the extent that it cannot be coupled to the detection light receiving unit 130. Therefore, the optical axis adjustment unit 151 increases the change width of the optical axis adjustment to increase the optical axis. The optical axis search is performed in all adjustable directions (step S114). At this time, the reception intensity signal Pa is larger than the predetermined threshold value P1, or the optical axis detection signal Pb is higher than the predetermined threshold value P2. Is also satisfied (ie, Pa> P1 or Pb> P2) (step S104). When this condition is satisfied, the optical axis adjustment unit 151 performs the determination in step S101 again.

  If the condition of step S104 is not satisfied, the optical signal may not reach the optical receiver 2, so the optical axis adjustment unit 151 stops the optical axis adjustment (step S115). In this case, the user is informed that communication is not possible, such as displaying an error.

  As described above, according to the optical receiver 2 according to the second embodiment of the present invention, in addition to the effects of the optical receiver 1 according to the first embodiment, the reception intensity signal Pa and the optical axis detection signal. By changing the optical axis adjustment width according to the respective sizes of Pb, more efficient optical axis adjustment can be performed.

  In order to realize a communicable state when the optical axes coincide with each other, when the minimum received signal strength indicating the strength of the minimum received signal that the signal light receiving unit 120 can communicate without error is Pmin, the threshold value P1 is It is desirable that it is equal to or smaller than Pmin or 1 to 2 dB larger than Pmin.

  In addition, since the optical signal deviated from the signal light receiving unit 120 due to the optical axis deviation is coupled to the detection light receiving unit 130, the smaller the threshold P2, the smaller the optical axis deviation can be detected. Become.

(Third embodiment)
Hereinafter, an optical receiver 3 according to a third embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 9 is a block diagram showing an example of a schematic configuration of the optical receiver 3 according to the third embodiment of the present invention. However, FIG. 9 shows the optical receiver 3 when there is no optical axis deviation. In FIG. 9, the optical receiver 3 is different from the second embodiment only in the operation of the optical axis adjustment unit 152. Here, the same components as those of the optical receiver 2 according to the second embodiment of the present invention are denoted by the same reference numerals, and description thereof is omitted.

  The operation of the optical axis adjustment unit 152 will be specifically described with reference to FIG. FIG. 10 is a flowchart illustrating an example of the operation of the optical axis adjustment unit 152. Referring to FIG. 10, the optical axis adjustment unit 152 sets a condition that the optical axis detection signal Pb is larger than a predetermined threshold value P0 (that is, Pb> P0) in order to determine whether or not there is an optical axis shift. It is determined whether or not it is satisfied (step S201). When this condition is satisfied, the optical axis is shifted within a range that can be detected by the detection light receiving unit 130, so the optical axis adjustment unit 152 is based on the optical axis detection signal Pb output from the optical axis detection unit 140. The optical axis is adjusted, and after a certain period, the condition of step S201 is determined again (step S211).

  When the condition of step S201 is not satisfied, there are a case where the optical axis is aligned and a case where the optical axis is shifted beyond a range that can be detected by the detection light receiving unit 130. Therefore, in order to distinguish these two cases, the optical axis adjustment unit 152 determines whether or not the condition that the reception intensity signal Pa is larger than the minimum reception signal intensity Pmin (that is, Pa> Pmin) is satisfied. (Step S202). When this condition is satisfied, the optical axis is matched and the reception intensity at which communication can be performed without error is obtained. Therefore, the optical axis adjustment unit 152 maintains the optical axis, and after a predetermined period, repeats step S201. The condition is determined (step S212).

  If the condition of step S202 is not satisfied, the optical axis adjustment unit 152 performs an optical axis search in all directions where the optical axis can be adjusted (step S213), and at this time, the optical axis detection signal Pb is from a predetermined threshold value P0. Is also satisfied (ie, Pb> P0) (step S203). When this condition is satisfied, the optical axis is shifted within a range that can be detected by the detection light receiving unit 130, so the optical axis adjustment unit 152 is based on the optical axis detection signal Pb output from the optical axis detection unit 140. The optical axis is adjusted, and after a certain period, the condition of step S201 is determined again (step S214).

  If the condition of step S203 is not satisfied, the optical signal may not reach the optical receiver 3, so the optical axis adjustment unit 152 interrupts the optical axis adjustment (step S215). At this time, the user is informed that communication is not possible, such as displaying an error.

  Note that the smaller the value of the threshold value P0, the smaller the optical axis deviation can be detected.

  As described above, according to the optical receiver 3 according to the third embodiment of the present invention, the detection and adjustment of the optical axis deviation can be performed with a simpler procedure as compared with the optical receiver 2 according to the second embodiment. Is possible.

  The optical receiver according to the present invention is useful as a configuration for improving the received light power of an optical space transmission device or the like. It can also be applied to uses such as an optical receiver of an optical sensor.

  Although the present invention has been described in detail above, the above description is merely illustrative of the present invention in all respects and is not intended to limit the scope thereof. It goes without saying that various improvements and modifications can be made without departing from the scope of the present invention.

1 is a block diagram showing an example of a schematic configuration of an optical receiver 1 according to a first embodiment of the present invention (no optical axis deviation) 1 is a block diagram showing an example of a schematic configuration of an optical receiver 1 according to a first embodiment of the present invention (with optical axis deviation) 1 is a perspective view showing a schematic configuration of an optical receiver 1 according to a first embodiment of the present invention (no optical axis deviation) Schematic diagram showing an outline of the optical element 110 according to the first embodiment of the present invention. The schematic diagram which shows the outline | summary of the light-receiving part 130 for a detection which concerns on the 1st Embodiment of this invention. The block diagram which shows an example of schematic structure of the optical receiver 2 which concerns on the 2nd Embodiment of this invention (no optical axis deviation) Block diagram showing an example of a schematic configuration of an optical receiver 2 according to the second embodiment of the present invention (with optical axis deviation) The flowchart which shows an example of operation | movement of the optical axis adjustment part 151 which concerns on the 2nd Embodiment of this invention. The block diagram which shows an example of schematic structure of the optical receiver 3 which concerns on the 3rd Embodiment of this invention. The flowchart which shows an example of operation | movement of the optical axis adjustment part 152 which concerns on the 3rd Embodiment of this invention. Block diagram showing the configuration of a conventional optical receiver The figure which shows an example of schematic structure of the light receiving element 930 for optical axis detection used with the conventional optical receiver

Explanation of symbols

1-3 Optical receiver 100 Condensing unit 110 Optical element 111 Transmission region 112 Branching region 113 Light beam cross section 120 Signal light receiving unit 121 Reception circuit unit 130 Detection light receiving unit 131-134 Photoelectric conversion region 140 Optical axis detection unit 150- 152 Optical axis adjustment unit 160 Image of transmitted light 161 Image of branched light 900 Total reflection mirror 901, 902 Condensing lens 910 Branch mirror 920 Signal light receiving element 930 Optical axis detection light receiving element 940 Optical axis detection circuit unit 950 Optical axis adjustment Part

Claims (15)

An optical receiver for receiving an optical signal transmitted to a medium through space,
A condensing unit for condensing the incident optical signal;
An optical element having a transmission region and a branch region, into which an optical signal collected by the light collecting unit is incident;
A light receiving unit for receiving light transmitted through the transmission region and performing photoelectric conversion;
A detection light receiving unit that receives the branched light branched in the branch region and outputs a detection intensity signal indicating the intensity of the branched light by photoelectric conversion;
An optical axis detection unit that detects an optical axis shift based on the detection intensity signal output from the detection light receiving unit and outputs an optical axis detection signal;
An optical axis adjustment unit that performs optical axis adjustment based on the optical axis detection signal,
The optical element is disposed at a position between the light collecting unit and the signal light receiving unit so that a central axis of the signal light receiving unit and a central axis of the transmission region substantially coincide with each other.
The optical receiver, wherein the branch region is a part of the optical signal and leaks light caused by an optical axis shift, and emits the branched light toward the detection light receiving unit.   In the optical element, a boundary shape between the transmission region and the branch region is annular, and a diameter of the boundary is larger than a diameter of a light beam cross section of the collected optical signal at the position of the optical element. The optical receiver according to claim 1, wherein:   The optical element has an annular shape at the boundary between the transmission region and the branch region, and the diameter of the boundary is larger than the diameter of the light beam cross section of the collected optical signal at the position of the optical element, 2. The optical receiver according to claim 1, wherein a shape of the boundary is substantially similar to a light beam cross section of the collected optical signal at the position of the optical element.   2. The optical receiver according to claim 1, wherein the transmission region is a hole having a diameter larger than a diameter of a beam cross section of the collected optical signal opened in the optical element.   The optical receiver according to claim 1, wherein the detection light-receiving unit is arranged concentrically with the signal light-receiving unit.   2. The optical receiver according to claim 1, wherein the detection light-receiving unit is arranged concentrically with the signal light-receiving unit and includes a plurality of regions for performing photoelectric conversion.   2. The optical receiver according to claim 1, wherein the branch region has a negative focal length and emits incident light toward the detection light receiving unit.   The optical receiver according to claim 7, wherein the branch region includes a Fresnel lens.   The optical receiver according to claim 7, wherein the branch region includes a diffractive lens.   The optical receiver according to claim 1, wherein the detection light-receiving unit is formed on the same substrate as the signal light-receiving unit. The signal light receiving unit further includes a reception circuit unit that outputs a reception intensity signal indicating a reception intensity of the transmitted light based on a signal obtained by photoelectrically converting the transmitted light.
The optical receiver according to claim 1, wherein the optical axis adjustment unit performs optical axis adjustment based on the optical axis detection signal and the reception intensity signal. The optical axis adjustment unit is
Maintaining the optical axis when the first condition that the intensity signal for reception is larger than a first threshold and the optical axis detection signal is smaller than a second threshold is satisfied,
Second condition that when the first condition is not satisfied, the reception intensity signal is larger than the first threshold value and the optical axis detection signal is larger than the second threshold value. If the second condition is satisfied, the optical axis adjustment is performed by reducing the change width of the optical axis adjustment,
A third condition that the reception intensity signal is smaller than the first threshold value and the optical axis detection signal is larger than the second threshold value when the second condition is not satisfied. If the third condition is satisfied, the optical axis adjustment is performed with the change width of the optical axis adjustment being medium,
If the third condition is not satisfied, the optical axis search is performed in all directions where the optical axis adjustment is increased and the optical axis adjustment is possible. At this time, the reception intensity signal is the first intensity signal. It is determined whether or not the fourth condition that the optical axis detection signal is greater than the threshold value or the optical axis detection signal is greater than the second threshold value is satisfied, and when the fourth condition is satisfied, Determine again whether the first condition is met,
The optical receiver according to claim 11, wherein the optical axis adjustment is interrupted when the fourth condition is not satisfied. The optical axis adjustment unit is
When the first condition that the optical axis detection signal is larger than a predetermined threshold is satisfied, the optical axis is adjusted based on the optical axis detection signal,
When the first condition is not satisfied, it is determined whether or not the reception intensity signal satisfies a second condition that the signal light receiving unit is larger than a minimum reception signal intensity with which the signal light receiving unit can communicate without error; If the second condition is satisfied, the optical axis is maintained,
If the second condition is not satisfied, an optical axis search is performed in all directions where the optical axis can be adjusted, and a third condition that the optical axis detection signal is larger than the predetermined threshold is satisfied. And when the third condition is satisfied, the optical axis is adjusted based on the optical axis detection signal,
The optical receiver according to claim 11, wherein the optical axis adjustment is interrupted when the third condition is not satisfied. An optical reception method executed by an optical receiver that receives an optical signal transmitted through a medium through space,
A condensing step of condensing the incident optical signal;
A step of transmitting, as transmitted light, an optical signal that matches the optical axis among the collected optical signals, and branching an optical signal that does not match the optical axis as branched light;
A signal receiving step for receiving the transmitted light and performing photoelectric conversion;
A light receiving step for detection that receives the branched light and outputs a detection intensity signal indicating the intensity of the branched light by photoelectric conversion;
An optical axis detection step of detecting an optical axis shift based on the detection intensity signal and outputting an optical axis detection signal;
An optical axis adjustment step of adjusting an optical axis based on the optical axis detection signal. An optical axis misalignment detection method executed by an optical receiver that receives an optical signal transmitted to a medium through space,
A condensing step of condensing the incident optical signal;
A step of transmitting, as transmitted light, an optical signal that coincides with an optical axis among the collected optical signals, and branching leakage light caused by an optical axis shift as branched light;
A signal receiving step for receiving the transmitted light and performing photoelectric conversion;
A light receiving step for detection that receives the branched light and outputs a detection intensity signal indicating the intensity of the branched light by photoelectric conversion;
An optical axis detection step of detecting an optical axis shift based on the detection intensity signal and outputting an optical axis detection signal.

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