JP2005172704A - Photodetection device and optical system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect a light flux having an incident angle of a wide range without a loss, in a photodetection device and an optical system of a compact type. <P>SOLUTION: This device is equipped with a position detection sensor 11 for detecting the light flux on a neutral position when an incident light flux enters a prescribed optical path along a main beam 15a on the axis, a cylindrical reflecting member 12 for deflecting the optical path along which the incident light flux advances to the outside of the position detection sensor 11 after deviating from the prescribed optical path, to the approaching side to the main beam 15a on the axis, and a position detection sensor 13 for receiving and detecting the light flux deflected by the cylindrical reflecting member 12. The amount of deviation of the incident light flux from the prescribed optical path is detected from detection outputs from the position detection sensors 11, 13. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a light detection device and an optical system. In particular, the present invention relates to various optical systems that perform light capturing and tracking capable of coarse tracking and fine tracking, for example, a light detection apparatus and an optical system that can be suitably used for a spatial light transmission apparatus.

  Conventionally, as a light detection device, a part of the light beam is branched by a beam splitter, received by a light sensor such as a quadrant detector, and the direction of the optical axis tilt of the light beam is detected by the position of the received light spot There is a known method with which to do this. For example, in Patent Document 1, the received signal light is divided by two half mirrors and led to a fine tracking sensor for a small incident angle variation and a coarse tracking sensor for a large incident angle variation.

In addition, a light detection method that does not use an optical sensor such as a quadrant detector has been proposed (see, for example, Patent Document 2). The apparatus used in the light detection method described in Patent Document 2 includes a vertical drive mirror that is tilt-driven in the vertical direction, a horizontal drive mirror that is tilt-driven in the horizontal direction, a condensing lens, and a light receiving element. ing. In order to detect and correct the inclination of the optical axis using this apparatus, first, the vertical drive mirror and the horizontal drive mirror are driven by two-dimensional control using a control voltage. Thereby, the light spot condensed on the light receiving element moves on the light receiving element while drawing a locus of a circle. At this time, the detection signal detected by the light receiving element fluctuates periodically according to the extent of the light spot protruding from the light receiving element. On the other hand, when the light spot does not protrude from the light receiving element, the detection signal is constant. Therefore, light can be detected without loss by adjusting the angle of each mirror so that the level of the detection signal does not change. Therefore, since the light receiving element serves as both detection of the optical axis shift and detection of the optical signal, an element for reducing the amount of light is not required, and there is no loss due to the received light.
JP 2000-292541 A (page 3-5, FIG. 1) Japanese Patent Laid-Open No. 5-122155 (Page 3, FIG. 1-2)

However, according to the method of Patent Document 1, when used for spatial light communication having an optical tracking function, a part of the received light is always used for detecting the inclination of the optical axis, so that it is detected by the light receiving element. The received light becomes weak. Especially in the case of long-distance communication, the received light itself is weak. If the light of the fine tracking and coarse tracking sensors is separated from this light by a half mirror, the light received by each sensor always loses light quantity in either the fine tracking or coarse tracking optical path, and the S / There was a problem that the N ratio decreased.
In Patent Document 2, since a light receiving element for signal detection is required to have a high-speed response, it is necessary to reduce the capacity of the light receiving element, and the light receiving area is generally small. Further, in order to detect without losing light, there is a premise that a part of the light spot always overlaps the light receiving area, so that the detection range of the optical axis deviation becomes extremely narrow. Therefore, there has been a problem that it is impossible to cope with a case where the incident angle is in a wide range.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a photodetector and an optical system that can detect a light beam having a wide range of incident angles without losing the amount of light for capturing and tracking. And

In order to solve the above-described problem, according to the first aspect of the present invention, there is provided a photodetector for detecting a deviation amount of an incident light beam from a predetermined optical path, wherein the incident light beam is relatively small when the deviation amount is relatively small. First light detecting means for detecting light by receiving light and optical path deflection for deflecting the incident light beam outside the light receiving range of the first light detecting means when the shift amount is relatively large And a second light detecting means for detecting light by receiving the light beam deflected by the optical path deflecting means, and at least one of the first light detecting means and the second light detecting means, The amount of deviation from the optical path is detected.
According to the present invention, when the amount of deviation of the incident light beam from the predetermined optical path is relatively small, it is possible to detect the amount of deviation of the incident light beam by detecting light with the first light detection means. When the amount of deviation is relatively large and the incident light beam enters outside the light receiving range of the first light detection means, the second light detection means can detect the light and detect the deviation amount of the incident light flux. Therefore, the shift amount can be detected by different light detection means corresponding to a wide range of shift amount.
Since the light beam incident on the second light detecting means is deflected by the optical path deflecting means, the optical path can be folded to be compact.
Further, since the incident light beam is incident on the first light detection means or the second light detection means or across them depending on the magnitude of the shift amount, the light quantity of the incident light beam is incident on any of the light detection means. The light can be detected without losing the light amount.

According to a second aspect of the present invention, in the light detection device according to the first aspect, the optical path deflecting unit causes an incident light beam shifted from the predetermined optical path to be on the traveling direction side of the predetermined optical path and on the optical axis of the predetermined optical path. The optical path is deflected in the approaching direction.
According to the present invention, an incident light beam that deviates from a predetermined optical path and travels outside the light receiving range of the first light detection means is converted by the optical path deflecting means to the traveling direction side of the predetermined optical path and the optical axis of the predetermined optical path (hereinafter simply referred to as the optical axis). The second light detection means can be arranged on the optical path of the predetermined optical path or in the vicinity of the optical path for light detection. Therefore, even if the incident angle of the incident light beam increases, light detection can be performed in a relatively narrow range on or near the extension of the predetermined optical path.

According to a third aspect of the present invention, in the light detection device according to the first or second aspect, the optical path deflecting unit includes a reflecting surface arranged symmetrically with respect to a plane passing through the optical axis of the predetermined optical path. And
According to the present invention, since the incident light beam is reflected symmetrically with respect to the symmetry plane (the plane passing through the optical axis of the predetermined optical path) on which the reflection surface is arranged, uniform light is used as the second light detection means. An optical element having detection sensitivity can be used. Therefore, the relationship between the light detection amount and the deviation amount of the incident light beam is simplified, and the deviation amount can be easily detected.

According to a fourth aspect of the present invention, in the photodetecting device according to the third aspect, the symmetrically disposed reflecting surfaces are composed of two pairs of plane reflecting surfaces, and each facing direction of the two pairs of plane reflecting surfaces. Are arranged so as to be orthogonal to each other.
According to the present invention, since the deflection directions by the light deflecting means are orthogonal to each other, a general-purpose optical element capable of obtaining a detection output for each of two orthogonal axial components as the second light detecting means, for example, a quadrant light receiver, a position A simple configuration using a detection light receiver or the like can be employed.

According to a fifth aspect of the present invention, in the photodetecting device according to the third or fourth aspect, the symmetrically disposed reflecting surfaces are disposed substantially parallel to a plane passing through the optical axis of the predetermined optical path. To do.
According to this invention, since the reflecting surface is arranged substantially parallel to the plane passing through the optical axis of the predetermined optical path, the arrangement of the reflecting surface is facilitated. Therefore, the optical path deflecting means can be manufactured at low cost and with high accuracy.

According to a sixth aspect of the present invention, in the light detection device according to any one of the first to fifth aspects, the first light detection means and the second light detection means are integrally provided.
According to the present invention, since the first and second light detecting means are provided integrally, the arrangement and assembly are facilitated, and the apparatus can be manufactured at low cost.

According to a seventh aspect of the present invention, in the light detection device according to any one of the first to sixth aspects, the detection surfaces of the first light detection means and the second light detection means are arranged on the same plane. The configuration.
According to this invention, since the detection surfaces of the first and second light detection means are arranged on the same plane, the arrangement and assembly are facilitated, and an inexpensive apparatus can be manufactured. Moreover, it can be set as a compact structure in an optical axis direction.

According to an eighth aspect of the present invention, in the light detection device according to any one of the first to seventh aspects, the center of the detection surface of the second light detection means is disposed on the optical axis of the predetermined optical path. And
According to this invention, since the center of the detection surface of the second light detection means is arranged on the optical axis, the detection means whose detection sensitivity is symmetrical with respect to the center of the light receiving surface is adopted as the second light detection means. The amount of deviation can be easily detected.

According to a ninth aspect of the present invention, in the light detection device according to any one of the first to eighth aspects, the optical path deflecting unit is filled with a light-transmitting medium having a refractive index different from that of the outside. And an optical element having an internal reflection surface formed on the boundary surface.
According to the present invention, since the optical path deflecting means is composed of an optical element having an internal reflection surface formed on the boundary surface with the outside, the number of parts can be reduced, and the assembly can be easily performed while maintaining the positional accuracy of the reflection surface with high accuracy. Can do. In particular, when the refractive index of the medium is larger than 1, when used in air or the like, the internal reflection surface can be configured as a total reflection surface. is there.

According to a tenth aspect of the present invention, in the optical system, the light detection device according to any one of the first to ninth aspects, a holding member that holds at least the optical detection device, and a deviation detected by the light detection device And a posture control means for controlling the posture of the holding member so that the incident light beam is incident along the predetermined optical path based on the amount.
According to the present invention, the amount of deviation of the incident light beam from the optical axis is detected by the light detection device according to any one of claims 1 to 9, and based on the result, the incident light beam is incident along the optical axis. Thus, the posture of the holding member can be controlled. Therefore, the change in the incident angle of the incident light beam can be tracked. That is, if another optical system for making the incident light beam incident on the holding member is disposed, the relative posture of the optical system can be controlled to be constant with respect to the incident light beam. As a result, an optical system capable of capturing and tracking light can be obtained. For example, an optical system suitable for a spatial light transmission system that can perform rough tracking and fine tracking can be constructed. And the effect similar to the invention in any one of Claims 1-9 can be provided.

According to an eleventh aspect of the present invention, in the optical system, the photodetector according to any one of the first to ninth aspects, and an incident optical path deflecting element that deflects the optical path of the incident light beam on the incident side of the photodetector. The incident light path deflecting element is controlled so that the incident light beam deflected along the optical path is incident along the predetermined optical path based on the amount of deviation detected by the light detection device.
According to this invention, the incident angle change of the incident light beam is tracked by controlling the incident light path deflecting element based on the deviation amount of the incident light beam detected by the light detection device according to any one of claims 1 to 9. Thus, the incident light beam can be captured. Then, the incident angle of the incident light beam can be detected by detecting the deflection angle of the incident optical path deflecting element. Further, it becomes possible to control the attitude of the entire optical system based on such detection information of the incident angle. For example, an optical system suitable for a spatial light transmission system that can perform rough tracking and fine tracking can be constructed. And the effect similar to the invention in any one of Claims 1-9 can be provided.

  According to the photodetector of the present invention and the optical system using the same, it is possible to detect light with respect to an incident light beam having a wide range of incident angles by the second light detection means, and to transmit such incident light beam to the optical path. Since the deflecting unit deflects the light to a relatively small area, there is an effect that a compact photodetector can be obtained. Further, at that time, there is an effect that it is possible to eliminate the light amount loss of the light beams incident on the first and second light detection means.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In all the drawings, even if the embodiments are different, the same or corresponding members are denoted by the same reference numerals, and redundant description is omitted.
[First Embodiment]
A photodetecting device according to a first embodiment of the present invention will be described.
FIG. 1A is a schematic optical path diagram for explaining the schematic configuration and operation of the photodetector according to the first embodiment of the present invention. FIG. 1B is a schematic optical path diagram for explaining the configuration of the modification. In addition, all are sectional views in the YZ plane described later.
As shown in FIG. 1A, the schematic configuration of the incident angle detection device 10 (photodetection device) of the present embodiment includes an aperture 16, a position detection sensor 11 (first light detection means), and a cylindrical reflection member 12. (Light deflection means) and a position detection sensor 13 (second light detection means).

  The aperture 16 is a light restricting member that has an opening such as a circle having a diameter D, for example, and shapes a light beam incident from the left side of the figure into a substantially circular shape. Reference numeral 15 a denotes an axial principal ray that passes through the center of the aperture of the aperture 16 and travels perpendicularly to the aperture 16.

The position detection sensor 11 is an optical element capable of detecting the center position of the light beam irradiated on the sensor surface 11a. For example, an image sensor such as a quadrant photoreceiver (quadrature PD), a position detection photoreceiver (PSD), a CCD, or a CMOS can be employed. In the following description, an example using a quadrant PD having a square detection area having a length h ₁ on one side so as to detect the displacement amount with high accuracy will be described.
Position of the position detection sensor 11, the sensor surface 11a is at a distance L ₁ from the aperture 16, the center of the sensor surface 11a is set to come on the axial principal ray 15a. In other words, the light beam 14a traveling along the axial principal ray 15a is disposed so as to be received at the neutral position of the sensor surface 11a. Therefore, the position detection sensor 11 can detect the amount of deviation from the optical path (predetermined optical path) traveling along the axial principal ray 15a.
As shown in FIG. 1A, the side h ₁ of the position detection sensor 11 is set so that a light beam having an incident half angle of view of θ ₁ or more outside the light receiving range is larger than the light beam diameter D of the light beam 14a. To do. That is,
h ₁ = 2 · L ₁ · tan θ ₁ −D (1)
And

The cylindrical reflection member 12 is a cylindrical tube having a square cross-section in which planar reflection surfaces 12A and 12B facing each other in parallel by a distance H and reflection surfaces 12C and 12D (not shown) are formed on the inner peripheral surface. It is a member. For example, a block material such as glass, metal, or synthetic resin with a square hole and a reflective film coating on the inner peripheral surface, or one with four surface reflectors bonded in a cylindrical shape it can. Further, the cylindrical reflection member 12 may be configured such that the inner peripheral side is filled with a medium having an appropriate refractive index and total reflection occurs on the reflection surface 12A or the like. In that case, there is an advantage that the reflection film coating can be omitted.
Thus, in this embodiment, the symmetrical surface that bisects the opposing reflecting surfaces 12A and 12B and the symmetrical surface that bisects the opposing reflecting surfaces 12C and 12D are orthogonal to each other.
The intersecting line is arranged so as to overlap the axial principal ray 15a. That is, in the XYZ rectangular coordinate system with the center O of the aperture 16 as the origin, if the Z axis coincides with the axial principal ray 15a and the symmetry plane of the reflecting surfaces 12A and 12B is the XZ plane, the YZ plane is It is a plane of symmetry of the reflecting surfaces 12C and 12D.
The X and Y axes are made to coincide with the two axes in the detection direction of the position detection sensor 11.
Note that the axial position of the cylindrical reflecting member 12 may be arranged at the rear stage (right side in the figure) of the position detection sensor 11 as shown in the figure, but if it does not hinder the optical path of the rear stage, the position detection sensor 11 may be arranged so as to be included inside the cylindrical reflecting member 12.

The position detection sensor 13 is an optical element that can detect the center position of the light beam irradiated on the sensor surface 13a. As with the position detection sensor 11, for example, a quadrant light receiver (four-part PD), a position detection light receiver (PSD), or an image sensor such as a CCD or CMOS can be employed. In the following, an example using a quadrant PD having a square detection region with a side length of h ₂ will be described (however, h ₂ ≦ H).
The arrangement position of the position detection sensor 13 is the rear stage of the cylindrical reflecting member 12, the sensor surface 13a is located at a distance L ₂ (where L ₁ <L ₂ ) from the aperture 16, and the center of the sensor surface 13a is the axis. It is set to come on the upper principal ray 15a.

  Although not shown, in the present embodiment, in order to operate the position detection sensors 11 and 13, an appropriate power source and a sensor output are subjected to waveform processing or arithmetic processing to detect the center position of the light beam to detect the light beam. Naturally, an incident angle detecting means for converting the incident angle into the incident angle is provided. The incident angle detection means can be constituted by, for example, a microcomputer programmed with arithmetic processing described later.

Next, operation | movement of the incident angle detection apparatus 10 is demonstrated for every optical path.
2A and 2B are schematic diagrams for explaining the operation of the position detection sensors 11 and 13 of the present embodiment. 2 (2a) and (2b) are graphs schematically showing an example of sensor outputs corresponding to each. In each graph, the horizontal axis is the incident angle, the vertical axis is the calculated value of the output of each sensor surface of the quadrant sensor, and the output of each sensor surface is represented by a, b as shown in FIGS. 2 (1a) and (1b). , C, and d, calculated values {(a + b) − (c + d)} for calculating the position (deviation amount) in the Y-axis direction are shown. The sign of the incident angle is positive in the counterclockwise direction with respect to the positive directions of the X axis and Y axis in the coordinate system of FIG.

As shown in FIG. 1A, when the incident angle of the incident light beam is relatively small, for example, all of the light beam reaches the sensor surface 11a and is received by the position detection sensor 11 like the light beam 14a. (Hereinafter, the optical path in this case is referred to as a central optical path).
On the other hand, the angle of incidence is relatively large, for example, approaches the angle theta _1, part of the light flux passes through the outside sensor surface 11a, the process proceeds to the tubular reflective member 12 side (hereinafter, referred to as boundary light path). Then, like the light beam 14b, the incident angle is the angle theta ₁ or more, all of the light beam passes through the detection area outside of the sensor surface 11a, is incident on the cylindrical reflective member 12 (hereinafter, referred to as periphery optical path).
For example, the principal ray 15b of the light beam 14b is incident on the reflecting surface 12A at the incident angle (90 ° −θ ₁ ) at the point Q and reflected as the light beam 14c. Then, the light reaches the sensor surface 13 a and is received by the position detection sensor 13.

Since the reflecting surface 12A is parallel to the axial principal ray 15a, the emission angle is (90 ° −θ ₁ ), and the light beam 14c advances toward the Z-axis positive direction while approaching the axial principal ray 15a. That is, as shown in FIG. 1A, the principal ray 15c is folded back like a line segment QS where it becomes a line segment QR without the reflecting surface 12A. As a result, it can be configured such that the center of the light beam on the sensor surface 13a approaches the point T as the incident angle of the incident light beam increases. Therefore, since the size of the sensor surface 13a does not exceed the cross-sectional area of the inner periphery of the cylindrical reflection member 12, it can be detected by the position detection sensor 13 that is smaller than the range of incident angles that can be detected. There is.

The position detection sensor 11 can detect the incident angle of the light beam passing through the central optical path and the boundary optical path. For example, as shown in FIG. 2 (1 a), when the incident angle changes from 0 ° to (−θ ₁ ) around the X axis and tilts from the light beam 14 a to the light beam 14 b, the calculated value of the sensor output is As shown in FIG. 2 (2a), the curve changes like a curve Oij.
A curve Oi indicates a change in the central optical path. In this optical path, the entire luminous flux is received by the sensor surfaces a, b, c, d. In this case, since the change in the incident angle is approximately proportional to the calculated value, even if the incident angle changes minutely, it can be easily detected with high accuracy.
A curve ij shows a change in the boundary optical path. In this optical path, since a part of the light beam passes outside the sensor surface 11a, the absolute value of the sensor output is attenuated, and as a result, the calculated value becomes zero. When the incident angle is (−θ ₁ ) or less, the sensor output is zero.

The position detection sensor 13 can detect the incident angle of the light beam passing through the boundary optical path and the peripheral optical path. For example, as shown in FIG. 2 (1b), when the light beam 14b is tilted around the X axis so that the incident angle is (−θ ₁ ) or less, the calculated value of the sensor output is shown in FIG. 2 (2b). As shown, it changes like a curve kmn. A curve Ok shows a state in which the sensor output becomes 0 because the light beam passing through the central optical path is blocked by the position detection sensor 11 and does not reach the position detection sensor 13.
A curve km indicates a change in the boundary optical path. In this optical path, a part of the light beam passes outside the sensor surface 11a and enters the sensor surfaces c and d of the position detection sensor 13, so that the calculated value increases in the negative direction. When the incident angle is (−θ ₁ ), all of the light beam is received on the sensor surfaces c and d like the light beam 14b, so that the calculated value is minimized. When the incident angle further increases in the negative direction, the light flux is also received by the sensor surfaces a and b, and the calculated value increases toward 0. Point n indicates that the light beam has entered the neutral position of the position detection sensor 13.
It should be noted that the case where the incident angle changes in the positive direction around the X axis and the case where there is a change around the Y axis are easily understood from the above description, and will not be described. For example, {(a + d) − (b + c)} may be used as the calculation value for detecting the angle around the Y axis.

The incident angle of the incident light beam can be uniquely determined from the graphs of FIGS. 2 (2a) and (2b). Two incident angles correspond to the converted value outputs of the position detection sensors 11 and 13, respectively, but one converted value output is 0 in the central optical path and the peripheral optical path, and the position detection sensor 11 in the boundary optical path. , 13 can be determined as one incident angle by using the fact that none of the converted value outputs of 13 is zero.
That is, when the converted value output of the position detection sensor 13 (11) that detects the peripheral optical path (center optical path) is 0, the conversion of the position detection sensor 11 (13) that detects the central optical path (peripheral optical path). The angle at which the absolute value of the incident angle corresponding to the value output is small (large) is the incident angle of the incident light beam.

On the other hand, when neither of the converted value outputs of the position detection sensors 11 and 13 is 0, an angle with a large (small) incident angle corresponding to the converted value output of the position detection sensor 11 (13) is an incident light beam. Of the incident angle. In this case, it goes without saying that the incident angles calculated from each are the same.
However, in this case, the detection accuracy differs depending on the amount of light incident on each sensor surface. Therefore, the angle at which the incident light beam is incident on the position detection sensors 11 and 13 by half is θ _B , and the incident angle θ in the range of | θ | ≦ | θ _B | If the incident angle θ in the range of | θ |> | θ _B | is output, the incident angle of the boundary optical path can be determined by the sensor having the larger amount of received light, which has the advantage of higher accuracy. . In addition, since the incident angle can be detected by either one of the position detection sensors 11 and 13, there is an advantage that detection output processing becomes easy.

Thus, in this embodiment, the incident angle can be continuously detected from a relatively small angle to a relatively large angle using the position detection sensors 11 and 13 respectively.
However, depending on the purpose of the incident angle detection, it may not be necessary to strictly detect the incident angle in the boundary optical path. For example, in the light capturing and tracking control, the position detection sensor 13 detects an angle control amount for making the incident light beam enter the position detection sensor 11 when the position detection sensor 13 is largely deviated from the target optical path (rough tracking). Is used for precise tracking to the target optical path. In this case, a sensor with coarse detection accuracy can be adopted as the position detection sensor 13.

Further, in order to detect a shift amount with higher accuracy, a sensor with a larger number of divisions can be used in place of the position detection sensor 13. For example, an optical element having a large number of divisions on the sensor surface, such as a position detection sensor 18 composed of a 16-division PD as shown in FIG.
The position detection sensor 18 causes the light beam to be simultaneously received by at least four sensor surfaces. For example, the illustrated light beam 14b is received by four surfaces of the sensor surfaces Ab, Ac, Bb, and Bc. At this time, if the four sensor surfaces Aa, Ab, Ac, Ad in the X-axis direction are the A portion, and the sensor surfaces Ba, Bb, Bc, Bd are the B portion, the sensor outputs are summed and expressed as outputs A, B. The relationship between the incident angle and the calculated value (AB) when the light beam 14b moves in the Y-axis direction is a graph as shown in FIG. 2 (2c).
That is, as long as the light beam center of the light beam 14b is within the A part and the B part, the calculated value shows a substantially linear change with respect to the incident angle (see the curve qs). Therefore, the incident angle can be detected with higher accuracy than the position detection sensor 13 by switching the calculation values by adjusting the outputs of the plurality of sensor surfaces in units of areas.

Next, a first modification of the present embodiment will be described.
FIG. 1B is a schematic optical path diagram for explaining a first modification of the light detection device according to the embodiment of the present invention.
In the incident angle detection device 17 of the present embodiment, the reflection optical element 29 is provided in the optical path incident on the position detection sensor 11 in the incident angle detection device 10, and the position detection sensor 11 is disposed off the axis of the axial principal ray 15a. The point is different.
The reflective optical element 29 is made of, for example, a plane mirror and the like, and bends the axial principal ray 15a at an appropriate position U at an appropriate angle. Then, the light beam 14d travels along the axial principal ray 15d after reflection. And the position detection sensor 11 is arrange | positioned so that the neutral position of the sensor surface 11a may be located on the axial principal ray 15d.

With such a configuration, the optical path length to the position detection sensor 11 can be adjusted without increasing the dimension in the axial principal ray 15a direction, so that a compact device can be obtained. Further, since the position detection sensor 11 can be arranged at an appropriate position, there is an advantage that the layout of the apparatus is easy.
In this way, even if the position detection sensor 11 has a non-detection area on the outer periphery of the sensor surface 11a, the light flux toward the position detection sensor 13 is not scattered by the non-detection area. There is an advantage that the incident angle can be detected with high accuracy.
Further, for example, by forming the reflective optical element 29 in a shape with less flux fluctuation, the incident angle θ ₂ incident on the position detection sensor 13 can be made shallower (see FIG. 1B).
The reflective optical element 29 may be a reflective element having power, and the light beam 14d may be converged light or diffused light to change the spot diameter on the position detection sensor 11 or the optical path length.

Next, a second modification of the present embodiment will be described.
FIG. 3 is a schematic perspective view for explaining a second modification of the photodetecting device according to the embodiment of the present invention.
The incident angle detection device 19 of this embodiment includes a transparent optical block 20 (optical path deflecting means) instead of the cylindrical reflecting member 12 of the incident angle detection device 10, and a position detection sensor 23 instead of the position detection sensors 11 and 13. The difference is that a condenser lens 21 is provided between the transparent optical block 20 and the position detection sensor 23.
The following briefly describes the differences.

The transparent optical block 20 is a regular quadrangular columnar member made of a medium having a refractive index of 1 or more, such as glass or synthetic resin, in which a light beam can enter and exit from both end faces. The side surfaces 20A and 20B and the side surfaces 20C and 20D of the regular quadrangular prism correspond to the reflecting surfaces 12A and 12B and the reflecting surfaces 12C and 12D of the cylindrical reflecting member 12, respectively, and are opposed to each other so that the light beam transmitted through the member can be totally reflected. The internal reflection surface is configured.
The symmetry axis of the regular quadrangular prism is arranged along the axial principal ray 15a.
On the incident side of the transparent optical block 20, a light-shielding aperture 20a is provided to prevent a light beam having a large incident angle as caused by the transparent optical block 20 from becoming noise in detecting the incident angle. However, the incident end face of the transparent optical block 20 has such a size that an incident light beam in an angle range that needs to detect an incident angle can be incident without being scattered.

The condensing lens 21 is a condensing optical element for allowing the light beam emitted from the transparent optical block 20 to have an appropriate spot diameter on the position detection sensor 23. Any condensing optical element may be used. For example, a spherical lens, a Fresnel lens, or the like may be employed.
The light blocking aperture 22 blocks flare light emitted from the condenser lens 21.

The position detection sensor 23 is formed by integrating a central position detection sensor 24 (first light detection means) and a peripheral position detection sensor 25 (second light detection means) with their light receiving surfaces arranged on the same plane. It is.
The center position detection sensor 24 is composed of a quadrant PD having sensor surfaces 24a, 24b, 24c, and 24d, and the neutral position thereof is disposed on the axial principal ray 15a.
The peripheral position detection sensor 25 includes sensor surfaces 25A, 25B, 25C, 25D, 25E, 25F, 25G, and 25H arranged so as to surround the four sides on the outer periphery of the central position detection sensor 24. Each of these sensor surfaces can detect the center position of the light beam received by each sensor surface. The center position can be detected. Therefore, an appropriate optical element such as a quadrant PD, PSD, or CCD can be adopted for each sensor surface.
The transparent optical block 20, the condensing lens 21, and the position detection sensor 23 receive the light beam that is not internally reflected by the transparent optical block 20 by the center position detection sensor 24, and the light beam that is internally reflected by the transparent optical block 20 is peripheral. They are arranged in such a positional relationship that they are received by the part position detection sensor 25.

Further, instead of the position detection sensor 11, a fiber end surface for optical communication or a light receiving surface such as a PD may be used. In this case, the size of the light receiving surface is approximately the same diameter as the incident light beam. However, in the case of the modification of the first embodiment, the size of the reflective optical element 29 is approximately the same diameter as the incident light beam.
By doing so, the incident angle of the incident light beam changes, so that the light beam outside the light receiving surface is incident on the position detection sensor 13 and the position is detected. Thereby, it can be set as the optical detection apparatus which can carry out light capture tracking without the light quantity loss of communication light.

According to such a configuration, the light beam 26 transmitted through the transparent optical block 20 having a relatively small deviation from the axial principal ray 15a is condensed on the center position detection sensor 24 by the condenser lens 21, and the accuracy is increased. The position is well detected. As a result, the incident angle of the light beam 26 is detected.
On the other hand, the light beam 27 having a relatively large deviation from the axial principal ray 15 a is deflected by the internal reflection surface in the transparent optical block 20, passes through the condenser lens 21, and is condensed on the peripheral position detection sensor 25. The position is detected by the peripheral position detection sensor 25 and the incident angle is detected.
Therefore, the incident angle of an incident light beam having a relatively wide range of incident angles can be detected. At this time, since the light beam having a large deviation amount is folded by the transparent optical block 20, it can be arranged in a relatively narrow space while having a wide range of incident angle detection. And the effective diameter of the condensing lens 21 can be made small. As a result, there is an advantage that a compact photodetection device can be configured.
Further, since the central position detection sensor 24 and the peripheral position detection sensor 25 are integrated, there is an advantage that an inexpensive apparatus with good assembling can be configured with high accuracy and ease. is there.

[Second Embodiment]
An optical system according to a second embodiment of the present invention will be described.
FIG. 4 is a schematic configuration diagram for explaining a schematic configuration of an optical system according to the second embodiment of the present invention.
The light transmission / reception system 30 according to the present embodiment is an optical system that enables light capture and tracking control by including the incident angle detection device 10 according to the first embodiment of the present invention.
The schematic configuration of the light transmission / reception system 30 includes a light transmission / reception optical system 33, a movable mirror 34 (incident optical path deflection element), and a light transmission unit in a housing 32 (holding member) held by a gimbal stage 44 (attitude control means). 38, beam splitters 35 and 36, a communication light detector 37, and an incident angle detector 10 are provided.

The light transmitting / receiving optical system 33 includes a substantial afocal optical system having a lateral magnification β. The incident light beam 51, which is a substantially parallel light beam incident from the aperture 31 provided in the housing 32, is appropriately imaged to be emitted as a substantially parallel light beam having a different light beam diameter, and the substantially parallel light beam is incident in the opposite direction. By doing so, it can be emitted from the aperture 31 as a substantially parallel light beam having a predetermined diameter. Here, reference numeral 50 denotes an axial principal ray of the optical system of the light transmission / reception system 30.
The intensity of the incident light beam 51 is modulated by communication information. When the communication light detector 37 that performs photoelectric conversion receives the light, the communication information is taken out and converted into an electric signal.
The movable mirror 34 controls the biaxial rotation by the movable mirror control means 34 a, thereby deflecting the incident light beam 51 according to a minute change in the incident angle of the incident light beam 51, and the incident position on the communication light detector 37. Is a mechanism for controlling the pressure substantially constant. For example, an optical deflection element such as a galvanometer mirror or optical MEMS can be employed.

The beam splitters 35 and 36 are branch optical elements that are arranged on the optical path deflected by the movable mirror 34 and branch the optical path. For example, it is possible to employ a prism or a plane parallel plate that can split an optical path by providing a half mirror surface, a polarization surface that branches light depending on the polarization direction, a wavelength selection surface that branches light depending on a wavelength difference, and the like.
The light transmitting unit 38 includes a laser light source 38 a and a collimating lens 38 b provided on the branch optical path side of the beam splitter 35. Then, divergent light modulated based on a predetermined information signal is emitted from the laser light source 38 a, converted into parallel light by the collimator lens 38 b, and incident on the axial principal ray 50 after being reflected by the beam splitter 35. Be able to.

The beam splitter 36 branches the incident light beam 51 that has passed through the beam splitter 35 into an optical path that is incident on the communication light detector 37 and an optical path that is directed toward the incident angle detector 10.
The description of the incident angle detection device 10 is omitted. Each sensor output from the position detection sensors 11 and 13 is input to the incident angle detection means 41 and converted into an incident angle.

The gimbal stage 44 is a moving mechanism that holds the casing 32 in a biaxial direction so that the posture can be controlled. The tilt drive unit 44a and the horizontal rotation drive unit 44b are held on the support base 44c, and rotate horizontally with the tilt drive unit 44a. Drive control means 44d for controlling the amount of movement with respect to the drive unit 44b is provided.
The horizontal rotation drive unit 44b and the tilt drive unit 44a can rotate around a vertical axis and rotate at a predetermined angle around the horizontal axis, respectively, by a mechanism such as a control motor (not shown) capable of controlling each rotation angle. It can be driven.
The drive control unit 44d is a unit for calculating a rotation drive amount of the tilt drive unit 44a and the horizontal rotation drive unit 44b based on a control signal generated by the control device 41 and performing a predetermined rotation drive.

The operation of the light transmission / reception system 30 will be briefly described.
When the incident light beam 51 travels and enters the axial principal ray 50, the movable mirror 34 is controlled to the neutral position, and the light beam emitted from the light transmission / reception optical system 33 is moved along the axial principal ray 50 by the movable mirror 34. The light is deflected, passes through the beam splitters 35 and 36, and enters the communication light detector 37 in an optimum state. Then, the incident light beam 51 branched by the beam splitter 36 is incident on the center of the position detection sensor 11.
In this state, the light beam incident on the beam splitter 35 from the light transmitting unit 38 is reflected by the movable mirror 34, travels in the direction opposite to the incident light beam 51 through the light transmitting / receiving optical system 33, and is emitted to the outside from the aperture 31. Is done. Therefore, communication can be performed in a stable state with another light transmission system at a remote position.

When the incident light beam 51 deviates from the axial principal ray 50 by the incident angle θ, a deviation of (β · θ) occurs on the communication light detector 37, but the incident angle detection device 10 detects the incident angle θ. The The incident angle detecting means 41 determines the magnitude of the incident angle θ or which of the position detection sensors 11 and 13 the incident light beam 51 is incident on.
When the absolute value of the incident angle θ is larger than a predetermined value, or when the incident light beam 51 is detected by the position detection sensor 13, the incident angle detection unit 41 controls the drive control unit 44d to control the biaxial movement amount. The signal 100 is output. Thereby, the shift amount of the incident light beam 51 is reduced by driving the gimbal stage 44 and controlling the posture of the housing 32. That is, a rough tracking operation is performed.
On the other hand, when the absolute value of the incident angle θ is smaller than the predetermined value, or when the incident light beam 51 is detected by the position detection sensor 11, the incident angle detecting means 41 is connected to the movable mirror control means 34a by the two axes of the movable mirror 34. The attitude control signal 101 is output. Thereby, the movable mirror 34 is rotated to deflect the optical path after the movable mirror 34. That is, the fine tracking operation is performed so that the incident light beam 51 deflected by the movable mirror 34 travels on the axial principal ray 50 without changing the attitude of the housing 32. Then, by repeating the fine tracking feedback, the incident light beam 51 is stably received by the communication light detector 37 in real time.
When the incident angle θ increases due to disturbance or the like, the movable mirror 34 is controlled to the neutral position, and the coarse tracking operation is started.

As described above, according to the light transmission / reception system 30 of the present embodiment, since the rough tracking and the fine tracking are selectively performed according to the amount of deviation of the incident angle of the incident light beam 51, the light receiving state of the communication light detector 37 is changed. It can be stabilized. As a result, highly accurate spatial light communication can be performed.
In that case, since the photodetection device according to the first embodiment of the present invention is used, an optical system having the same functions and effects as those of the photodetection device according to the first embodiment can be obtained.
That is, since fine tracking and rough tracking are performed by the light beam branched by the beam splitter 36, an incident angle detection device is provided for fine tracking and rough tracking, respectively, and the light beam directed to the communication light detector 37 is branched. Compared with this optical system, an optical system with less light loss can be obtained, and a highly accurate and compact optical system can be obtained.

In the description of the first embodiment, the case where the reflecting surface of the light deflecting means is parallel and symmetric with respect to a plane passing through the axial principal ray has been described as an example. Alternatively, they may be asymmetrically opposed. For example, when the change range of the incident angle of the incident light beam is biased, if the detection sensitivity of the light detection means is biased, it may be possible to perform light detection with higher accuracy.
In the description of the first embodiment, the case where the detection output of the quadrant sensor changes linearly with respect to the shift amount in the central optical path has been described. However, if the curve is a monotonous curve, the incident angle detection and control is performed. Is not limited to a straight line.

  In the description of the second embodiment, the spatial optical communication system provided with the light capturing and tracking function is described as an example of the optical system. However, this is an example and is not limited to this application. . For example, another optical system such as a telescope having a light capturing and tracking function may be used. Further, since the light detection device according to the first embodiment of the present invention can continuously detect the light receiving position on the light detection means from a relatively small angle to a relatively large angle, for example, an angle measurement system or the like. Also good.

  In the above description of the second embodiment, an optical system that performs fine tracking by controlling the incident optical path deflecting element 34 has been described. However, for example, the incident optical path deflecting element 34 is omitted, and the attitude control unit is configured to perform coarse tracking. The fine tracking operation may be performed separately by the fine tracking posture control means.

It is a schematic optical path diagram for demonstrating schematic structure and operation | movement of an example of the photodetector which concerns on the 1st Embodiment of this invention, and its modification. It is the schematic diagram and graph for demonstrating the structure and operation | movement of an example of the 1st and 2nd light detection means which concern on the 1st Embodiment of this invention, and its modification. It is a schematic perspective view for demonstrating the 2nd modification of the photon detection apparatus which concerns on the 1st Embodiment of this invention. It is a schematic block diagram for demonstrating schematic structure of the optical system which concerns on the 2nd Embodiment of this invention.

Explanation of symbols

10, 17, 19 Incident angle detector (photodetector)
11 Position detection sensor (first light detection means)
12 cylindrical reflection member (light deflection means)
12A, 12B, 12C, 12D Reflective surfaces 13, 18 Position detection sensor (second light detection means)
14a Luminous flux (incident luminous flux)
15a, 15d, 50 axial principal ray 20 transparent optical block (light deflecting means)
20A, 20B, 20C, 20D Side surface (internal reflection surface)
21 Condensing lens 23 Position detection sensor 24 Center part position detection sensor (first light detection means)
25 Peripheral position detection sensor (second light detection means)
29 reflective optical element 30 light transmission / reception system (optical system)
32 Housing (holding member)
33 Transmitting / receiving optical system 34 Movable mirror (incident optical path deflecting element)
35, 36 Beam splitter 37 Communication light detector 38 Light transmitter 44 Gimbal stage (Attitude control means)

Claims (11)

A light detection device that detects a deviation amount of an incident light beam from a predetermined optical path,
First light detection means for detecting light by receiving the incident light beam when the amount of deviation is relatively small;
An optical path deflecting means for deflecting the incident light flux outside the light receiving range of the first light detecting means when the shift amount is relatively large;
Second light detecting means for detecting light by receiving the light beam deflected by the optical path deflecting means,
An optical detection apparatus, wherein the amount of deviation of the incident light beam from a predetermined optical path is detected by at least one of the first and second light detection means.   2. The light detection according to claim 1, wherein the optical path deflecting unit deflects an incident light beam deviating from the predetermined optical path in a direction in which the predetermined optical path travels and approaches the optical axis of the predetermined optical path. apparatus.   The optical detection device according to claim 1, wherein the optical path deflecting unit includes a reflecting surface arranged symmetrically with respect to a plane passing through the optical axis of the predetermined optical path. The symmetrically arranged reflecting surfaces consist of two pairs of plane reflecting surfaces,
The light detection device according to claim 3, wherein the opposing directions of the two pairs of planar reflection surfaces are arranged to be orthogonal to each other.   5. The photodetecting device according to claim 3, wherein the symmetrically arranged reflecting surfaces are arranged substantially parallel to a plane passing through an optical axis of the predetermined optical path.   6. The light detection device according to claim 1, wherein the first light detection means and the second light detection means are provided integrally.   The light detection apparatus according to claim 1, wherein detection surfaces of the first light detection unit and the second light detection unit are arranged on the same plane.   The light detection device according to claim 1, wherein a center of a detection surface of the second light detection means is disposed on an optical axis of the predetermined optical path.   9. The optical path deflecting unit comprises an optical element filled with a light-transmitting medium having a refractive index different from that of the outside and having an internal reflection surface at a boundary surface with the outside. The light detection device according to any one of the above. The light detection device according to any one of claims 1 to 9,
A holding member for holding at least the optical detection device;
An optical system comprising: an attitude control unit configured to control an attitude of the holding member so that the incident light beam is incident along the predetermined optical path based on a deviation amount detected by the light detection device. The light detection device according to any one of claims 1 to 9,
An incident optical path deflecting element that deflects the optical path of the incident light beam on the incident side of the photodetecting device;
An optical system that controls the incident optical path deflecting element so that an incident light beam deflected along the optical path is incident along the predetermined optical path based on a deviation amount detected by the light detection device.

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