JPH0862096A - Device for measuring beam spread angle - Google Patents

Abstract

PURPOSE: To provide beam spread angle measuring instrument which can easily and accurately measure a spread angle for a flux of light emitted from a light space transmission device. CONSTITUTION: The title device is provided with angle detection systems 21, 23, 26, and 28 and 22, 24, 27, and 29 for detecting angles θ1 and θ2 of a flux of light L1 for a light axis and a spread angle detection system 30 for detecting a spread angle θ as an entire flux of light L1 based on the angle detection results θ1 and θ2 at both edges of the flux of light L1 in a direction for crossing the light axis.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a beam divergence angle measuring device, and can be applied to, for example, an adjusting device of an optical space transmission device for transmitting an information signal to a transmission target through a light beam propagating in space.

[0002]

2. Description of the Related Art Conventionally, in an optical space transmission device, a desired information signal is transmitted through a laser beam propagating in space so that it can be easily installed and used for television relay or the like. .

That is, in an optical space transmission system formed by this type of optical space transmission device, for example, a pair of optical space transmission devices face each other at points where it is difficult to easily install a cable or the like. And a laser beam is transmitted and received between the pair of optical space transmission devices.

Here, the pair of optical space transmission devices have the same structure, and as shown in FIG. 7, the lens barrel 2 is provided in a predetermined housing.
It is formed by housing. Here, the lens barrel 2 holds an optical system inside the lens barrel 2, and in the optical space transmission device 1, the laser beam L1 is emitted from the lens barrel 2 toward the transmission target, and also comes from the transmission target. Laser beam L2
To receive.

Further, in the optical space transmission apparatus 1, the direction of the lens barrel 2 is moved vertically and horizontally by an actuator as shown by arrows a and b with reference to the incident direction of the laser beam L2 coming from the transmission object. Thus, the emission direction of the laser beam L1 is corrected to irradiate the transmission target.

That is, the lens barrel 2 has the laser diode 3 arranged above the optical axis of the lens barrel 2 and drives the laser diode 3 with an information signal S1 used for transmission of, for example, a video signal. As a result, the optical space transmission device 1
A linearly polarized laser beam L1 modulated by the information signal S1 is emitted from the laser diode 3, and the laser beam L1 is converted into a substantially parallel light beam by the convex lens 4.

Further, the optical space transmission device 1 reflects the laser beam L1 in the optical axis direction by the deflection beam splitter 5 arranged on the optical axis of the lens barrel 2 and emits it toward the front concave lens 6. Here, the concave lens 6 converts the laser beam L1 into divergent light and emits it toward the large-diameter lens 7, and the large-diameter lens 7 causes the laser beam L1 to approach the substantially parallel rays.
The spread angle θ of 1 is corrected and sent to the transmission target.

Here, the spread angle θ is selected to be a small angle of 1 [mrad] in the optical space transmission device 1,
Thereby, when the laser beam L1 is irradiated toward the transmission target, the laser beam L1 can surely irradiate the transmission target, and the laser beam L1 can be received by the transmission target with a sufficient light amount. There is.

When emitting the laser beam L1, when the optical space transmission device 1 looks at the optical space transmission device 1 from the front of the large-diameter lens 7, the polarization plane of the laser beam L1 is oriented with respect to the vertical direction. The laser diode 3 is held so as to be tilted at 45 degrees. As a result, the optical space transmission device 1 transmits and receives the laser beams L1 and L2 for the laser beam L1 to be transmitted to the transmission target and the laser beam L2 coming from the transmission target by commonly using the concave lens 6 and the large diameter lens 7. This laser beam L1 and L
The deflecting beam splitter 5 is used to easily separate the two.

That is, in the optical space transmission device 1, the large-diameter lens 7 has a laser beam L coming from a transmission target.
2 is received and guided to the concave lens 6, where it is converted into substantially parallel rays and emitted to the deflection beam splitter 5. The polarization beam splitter 5 transmits the laser beam L2 and outputs it to the beam splitter 9 by holding the polarization plane of the laser beam L2 at an angle inclined by 90 degrees with respect to the polarization plane of the laser beam L1. Beam splitter 9
Reflects a part of the laser beam L2 to be emitted to the convex lens 10, and transmits the rest to be emitted to the convex lens 11.

The convex lens 11 applies a laser beam L2 to a light receiving element 12 formed of an avalanche photodiode.
Thus, the optical free space transmission apparatus 1 receives the information signal sent from the transmission target, after the output signal S2 of the light receiving element 12 is subjected to current-voltage conversion processing and then demodulated.

On the other hand, the convex lens 10 focuses the laser beam L2 on the light receiving element 13 formed by the position detecting element, and the light receiving element 13 changes the signal level according to the focusing position of the laser beam L2. Then, the position detection signal S3 is output. As a result, the optical space transmission device 1 performs a current-voltage conversion process on the position detection signal S3 and then outputs the position-detection signal S3 to the servo circuit, so that the lens barrel 2 is oriented so that the focus position of the laser beam L2 becomes a specified position. It can be changed vertically and horizontally. As a result, the optical space transmission device 1 changes the direction of the lens barrel 2 with reference to the incident direction of the laser beam L2 coming from the transmission target, and irradiates the laser beam L1 correctly toward the transmission target. There is.

[0013]

However, the conventional optical space transmission device 1 has a problem that the measurement of the divergence angle θ of the laser beam L1 is complicated.

That is, as a method of measuring the spread angle θ in accordance with the actual use condition, for example, the optical space transmission device 1
There is a method in which a wall surface is formed at a position separated by about 200 [m] from and the laser beam L1 is emitted toward this wall surface. That is, by measuring the beam diameter of the laser beam L1 formed on this wall surface and measuring the beam diameter of the laser beam L1 near the large-diameter lens 7,
The divergence angle θ can be measured by the difference between the two beam diameters and the distance to the wall surface.

However, in the case of this method, it is possible to obtain a measurement result according to the actual use condition, but there is a drawback that a large facility is required for the measurement. In particular, in order to improve the measurement accuracy of the spread angle θ, it is necessary to set a large distance to the wall surface. For example, when it is performed outdoors, the influence of the weather cannot be avoided. Also, since it is necessary to measure the beam diameter on the wall surface far from the optical space transmission device, it is necessary to communicate the measurement result to the optical space transmission device side by side to adjust the spread angle θ, which is complicated. And there is also a drawback that it requires manpower.

On the other hand, a method of arranging a collimator on the front surface of the optical space transmission device 1 and measuring the spread angle θ by this is also conceivable. That is, the collimator is formed by disposing a lens having a large diameter and a long focal length at the tip of a lens barrel, and disposing a monitor device near the focal position of this lens, and moving this monitor device in the optical axis direction to move this lens. The parallelism of the light incident on this lens can be observed by detecting the condensing position by. The divergence angle θ can be measured by injecting the laser beam L1 into the collimator and measuring the focus position of the laser beam L1.

However, in practice, when a collimator is used, it is difficult to accurately detect the position where the beam diameter of the laser beam L1 is the smallest (that is, at the focus position). Therefore, in the case of this method. , There is a problem of poor reproducibility.

The present invention has been made in consideration of the above points, and an object of the present invention is to propose a beam divergence angle measuring device which can measure the divergence angle of a beam of this kind simply and accurately.

[0019]

In order to solve such a problem, in the present invention, at both ends of the light beam L1 in the direction crossing the optical axis, the angles θ1, θ of the light beam L1 with respect to the optical axis are set.
2 is detected respectively and the first and second angle detection results θ1
And the second angle detection systems 21 and 2 which output θ2 and θ2.
3, 26, 28 and 22, 23, 27, 29 and the light flux L based on the first and second angle detection results θ1 and θ2.
1 Spread angle detection system 3 for detecting the spread angle θ as a whole
Be prepared with 0 and.

In particular, these first and second angle detection systems 21, 23, 26, 28 and 22, 23, 27, 29.
Is a lens system 21 and 22 for receiving and condensing the light flux at both ends of the light flux L1, and a position detection signal S _x1 for receiving the condensed light flux and changing the signal level according to the converging position of the light flux. _-1 , S _x1-2 and S _x2-1 , S _x2-2 and the light receiving elements 23 and 24 which output S _x1-1 , S _x1-2 and S _x2-1 , S _x2-2 . Based on this, the signal processing circuits 26, 28 and 27, 30 for outputting the first and second angle detection results θ1 and θ2, respectively, are formed.

[0021]

At both ends of the light beam L1 in the direction crossing the optical axis,
Angles θ1 and θ2 of the light beam L1 with respect to the optical axis are detected to obtain first and second angle detection results θ1 and θ2, respectively, and the light beam L1 is obtained based on the first and second angle detection results θ1 and θ2. By detecting the spread angle θ as a whole, the spread angle θ can be measured easily and accurately.

In particular, the first and second angle detection systems 21, 2
3, 26, 28 and 22, 23, 27, 29, and lens systems 21 and 22 for receiving and condensing a light beam, respectively.
The position detection signals S _x1-1 , S _x1-2, and S, which receive the condensed light flux and whose signal level changes in accordance with the _focal position of the light flux
_Based on the light receiving elements 23 and 24 that output _x2-1 and S _x2-2 , and the position detection signals S _x1-1 , S _x1-2 and S _x2-1 and S _x2-2 , the first and second The divergence angle θ can be measured with a simple structure by forming the angle detection results θ1 and θ2 with the signal processing circuits 26, 28 and 27, 30.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

In FIG. 2, reference numeral 20 indicates a beam divergence angle measuring device, and in this embodiment, a lens barrel 2 of the optical space transmitting device.
Is placed in front of the beam divergence measuring device 20 to measure the divergence angle of the laser beam.

Therefore, the beam divergence angle measuring device 20 is
The lens barrel 2 is held integrally with a jig for installing the lens barrel 2. In the optical space transmission device, after the lens barrel 2 is assembled, the lens barrel 2 is mounted on this jig to adjust the optical system. . At this time, the lens barrel 2 is held by the jig so that the major axis of the ellipse-shaped beam spot SP of the laser beam L1 is in the horizontal direction (that is, in the x direction in FIG. 2). It is designed to be.

On the other hand, the beam divergence angle measuring device 20
Has convex lenses 21 and 22 arranged side by side in the horizontal direction so as to face the large-diameter lens held by the lens barrel 2. In the optical space transmission device 1, the laser beam L1 is directed to the convex lenses 21 and 22. It is mounted on the jig so that it is not blocked. The beam divergence angle measuring device 20 uses the convex lens 2
The light receiving elements 23 and 24 are arranged on the focal planes 1 and 22.

Here, the light receiving elements 23 and 24 respectively have four types of position detection signals S _x1-1 and S x whose signal levels change in the x and y directions according to the focal position of the light beam.
_x1-2 , S _y1-1 , S _y1-2 and S _x2-1 , S _x2-2 , S _y2-1 , S
It adapted to output _Y2-2, beam divergence angle measuring device 20, the output signal S _x1-1 for x-direction of these output signals _{S x1-1} ~S _y2-2, S x1-2 and S _x2-1 , S _x2-2
Then, the divergence angle θ of the laser beam L1 is measured.

That is, as shown in FIG. 3, the convex lens 21
When the laser beam L1 is incident with an inclination to the optical axes of the laser beams 22 and 22, the focus position P of the laser beam L1 formed on the position detection elements 23 and 24 is convex lenses 21 and 2 accordingly.
The optical axis of 2 is separated from the point O where the light receiving surfaces of the position detection elements 23 and 24 intersect, and the distance from the condensing position P to the point O changes according to this inclination. In FIG. 3, the light receiving elements 23 and 24 will be described by taking a cross section in the x direction.

Here, the position detecting elements 23 and 24 are
Since the convex lenses 21 and 22 are arranged on the focal planes, the focal lengths of the convex lenses 21 and 22 are set to f, and the distances from this point O to the condensing positions P in the respective light receiving elements 23 and 24 are respectively set. Assuming x1 and x2, the inclinations θ1 and θ2 of the laser beam L1 incident on the respective convex lenses 21 and 22 can be expressed by the following equations.

[0030]

[Equation 1]

Therefore, in each light receiving element 23 or 24,
If this distance x1 or x2 can be detected, when the optical axis of the convex lens 21 or 22 and the optical axis of the laser beam L1 are held parallel to each other, this inclination θ1 or θ
2 can be used as the divergence angle θ of the laser beam L1. On the other hand, when the optical axis of the laser beam L1 is deviated from the optical axis of the convex lens 21 or 22, the spread angle θ of the laser beam L1 is calculated from the inclinations θ1 and θ2.
Is given by

[Equation 2] Can be detected with.

Here, when the optical axes of the convex lenses 21 and 22 are held at the centers of the light receiving surfaces of the light receiving elements 23 and 24, which are the position detecting elements of this type, the length of the light receiving surface in the x direction is determined. Letting A be the following equation between this length A and the distance x to the focus position:

(Equation 3) The relational expression of can be obtained. Where I1 and I2 are
The current values of the position detection signals S _x1-1 and S _x1-2 , S _x2-1 and S _x2-2 obtained from the electrodes arranged in the x direction are shown.

As a result, the relational expression of the expression (3) is changed to the expression (1)
Substituting into the formula, the following formula

[Equation 4] It is possible to obtain the relational expression of ## EQU1 ## and thus the currents I1 and I2 can be detected by the light receiving elements 23 and 24, and the divergence angle of the laser beam L1 can be detected from the expression (2).

On the basis of this detection principle, the beam divergence angle measuring device 20 is provided with the light receiving elements 23 and 2 as shown in FIG.
Among the four output signals S _{x1-1 to} S _y2-2 , the output signals S _x1-1 , S _x1-2 and S _x2-1 , S _x2-2 in the x direction are supplied to the current-voltage conversion circuits 26 and 27, respectively. Output and convert current to voltage here. Furthermore, the output signals of the current-voltage conversion circuits 26 and 27 are output to the angle calculation circuits 28 and 29, respectively, and the calculation processing of the above-mentioned equation (4) is executed here to obtain the inclination θ.
1 and θ2 are detected. Further, the beam divergence angle measuring device 20 subtracts the detection results of the inclinations θ1 and θ2 from the subtraction circuit 3
Then, the beam divergence angle θ is detected by executing the arithmetic processing of the equation (2).

Specifically, the beam divergence angle measuring device 20
Measures the beam divergence angle θ with the circuit configuration shown in FIG. That is, the beam divergence angle measuring device 20 _inputs the output signals S _x1-1 and S _x1-2 of the light receiving element 23 in the x direction to the inverting input terminals of the operational amplifier circuits 32 and 33, respectively. Here, each of the operational amplifier circuits 32 and 33 has a non-inverting input terminal grounded, and forms a feedback circuit with a parallel circuit of the resistor 34 and the capacitor 35 and a parallel circuit of the resistor 36 and the capacitor 37, whereby the output signal S _x1-1 ,
S _x1-2 is converted into a current voltage and output.

The operational amplifier circuit 38 inputs the output signals of the operational amplifier circuits 32 and 33 to the inverting input terminal via the input resistors 39 and 40, respectively, and feeds the output signal back to the inverting input terminal by the feedback resistor 41. Has been done. Further, the operational amplifier circuit 38 grounds the non-inverting input terminal, thereby adding and outputting the output signals of the operational amplifier circuits 32 and 33. Thus, the operational amplifier circuit 32 has the second right side of the equation (4).
The denominator of the term will be calculated.

On the other hand, the operational amplifier circuit 42 inputs the output signal of the operational amplifier circuit 32 to the inverting input terminal via the input resistor 43, and the output signal of the operational amplifier circuit 33 is input resistor 4.
It is input to the non-inverting input terminal via 4. Further, in the operational amplifier circuit 42, the output signal is fed back to the inverting input end by the feedback resistor 45, and the non-inverting input end is grounded by the resistor 46. As a result, the operational amplifier circuit 42 executes the subtraction process between the output signals of the operational amplifier circuits 32 and 33,
The numerator of the second term on the right side of the equation (4) will be calculated.

Further, the operational amplifier circuit 42 inputs the offset voltage V1 to the inverting input terminal via the resistor 47, and the beam divergence angle measuring device 20 can adjust the offset voltage V1. As a result, the beam divergence angle measuring device 20 can detect the offset voltage V
1 is adjusted to correct the offset voltage of the operational amplifier circuits 32, 33, 38, 42, and the positional deviation of the light receiving element 23 with respect to the convex lens 21 is corrected to improve the measurement accuracy of the spread angle θ.

The division circuit 50 uses the operational amplifier circuit 42.
The output signal is output by dividing it by the output signal of the operational amplifier circuit 38, whereby the operational processing of the equation (4) is executed together with the operational amplifier circuits 38 and 42, and the processing result is output. At this time, the division circuit 50 amplifies the division result and outputs the result.

(Equation 5) As shown in, the 10-fold division result Vθ1 is output. Therefore, by substituting the equation (4) into the equation (5), the division circuit 50

(Equation 6) The angle detection signal Vθ1 represented by the relational expression is output. Thus, the beam divergence angle measuring device 20 improves the measurement sensitivity by amplifying and outputting the division result.

Similarly, the beam divergence measuring device 20
Is an output signal S _x2-1 of the light receiving element 24 in the x direction,
S _x2-2 is input to the inverting input terminals of the operational amplifier circuits 52 and 53, respectively. Here, the operational amplifier circuits 32 and 33 form a current-voltage conversion circuit having a feedback resistor 54, a feedback capacitor 55, a feedback resistor 56, and a feedback capacitor 57, respectively, while grounding their non-inverting input terminals, respectively, and thereby the output signal. S _x2-1 and S _x2-2 are converted into current and voltage and output.

The operational amplifier circuit 58 includes input resistors 59 and 6
0 and the feedback resistor 61 form an adder circuit, which adds the output signals of the operational amplifier circuits 42 and 43 and outputs them. The operational amplifier circuit 62 forms a subtraction circuit together with the input resistors 63 and 64, the feedback resistor 65 and the ground resistor 66, and the operational amplifier circuit 5
Subtraction processing is executed between the output signals of 2 and 53, and the processing result is output.

Further, the operational amplifier circuit 62 inputs the offset voltage V2 to the inverting input terminal via the resistor 67, whereby the beam divergence angle measuring apparatus 20 adjusts the offset voltage V1 also on the side of the light receiving element 24. The divergence angle θ can be detected with high accuracy.

The division circuit 70 has the operational amplifier circuit 62.
The output signal of 1 is divided by the output signal of the operational amplifier circuit 58 and output, and the processing result is output. At this time, the division circuit 50 amplifies and outputs the division result,
The following equations corresponding to equations (5) and (6)

(Equation 7) The calculation processing result is output to improve the measurement sensitivity of the beam divergence angle measuring apparatus 20.

The operational amplifier circuit 71 inputs the output signals of the division circuits 50 and 70 to the inverting input terminal and the non-inverting input terminal via the resistor 72 and the semi-fixed variable resistor 73, respectively. In this operational amplifier circuit 71, a negative feedback circuit is formed by the feedback resistor 74, and the non-inverting input terminal is grounded by the resistor 75, thereby forming a subtraction circuit. As a result, the operational amplifier circuit 71 executes the subtraction process between the output signals of the division circuits 50 and 70.

[Equation 8] The calculation processing result represented by is output. Thus, the beam divergence angle measuring device 20 outputs the beam divergence angle detection result Vθ via the operational amplifier circuit 71.

Here, the angles θ1 and θ2 are angles detected in the opposite directions with respect to the optical axis of the laser beam L1, and also the optical axes of the convex lenses 21 and 22 and the optical axis of the laser beam L1. Since the values are equal when the two are held in parallel, the equation (8) in this case becomes
Letting the angles θ1 and θ2 be the angle θ, the following equation

[Equation 9] Can be represented by

Therefore, the equation (9) is modified to obtain the following equation.

[Equation 10] Can be obtained, and the detection sensitivity can be determined from this. In this embodiment, the focal length f of the convex lenses 21 and 22 is selected to be 250 [mm], and the light receiving elements 23 and 24 having the light receiving surface length A of 4.1 [mm] are used. Substituting this value into equation (10),

[Equation 11] It is possible to obtain the relational expression of ## EQU1 ## and to obtain practically sufficient detection sensitivity.

Further, the operational amplifier circuit 71 includes an input resistor 76.
The offset voltage V3 is input to the inverting input terminal via the
3 can be adjusted. Thereby, the beam divergence angle measuring device 20 corrects the offset generated in the division circuits 50 and 70, etc., and improves the measurement accuracy. Also, a semi-fixed variable resistor 73
Is adjusted to adjust variations in gain between the division circuits 50 and 70, thereby improving the measurement accuracy.

Thus, the beam divergence angle measuring device 20 outputs the angle measurement result Vθ via the test point T1 formed on the output side of the operational amplifier circuit 71.

By the way, as a premise for measuring the divergence angle θ in this way, the lens barrel 2 is used as the beam divergence angle measuring device 20.
Must be set correctly. Therefore, in this embodiment, the operational amplifier circuits 38, 42, 58 and 6 are used.
Test points T2 to T5 are formed on the respective output sides of 2 and whether or not the output signals of the test points T2 and T3, T4 and T5 are respectively input to the XY axis of the oscilloscope and are maintained within the specified range. By judging,
The light amount of the laser beam L1 is confirmed, and it is also confirmed that the optical axis of the laser beam L1 is not largely deviated from the beam divergence angle measuring device 20.

Further, in the beam divergence angle measuring device 20,
Test points T6 and T7 are formed on the output sides of the division circuits 50 and 70, respectively, whereby the output signals of the test points T6 and T7 are monitored in the same manner to shift the optical axis, saturate the operational amplifier circuit 38, etc. The saturation of the division circuits 50 and 70 is monitored.

Further, the beam divergence angle measuring device 20 includes position detection signals S _y1-1 and S y of the light receiving elements 23 and 24 in the y direction.
_y1-2 and S _y2-1, using _S y2-2, detects whether the lens barrel 2 is properly set. That is, when the light amount of the laser beam L1 is inappropriate, or when the optical axis of the laser beam L1 is largely deviated, test points T2 to T7
The output signal of can be monitored and confirmed. On the other hand, it may be considered that the optical axis of the laser beam L1 is not accurately set.

Therefore, as shown in FIG. 5, the beam divergence angle measuring apparatus 20 outputs the output signals S _y1-1 and S _y1-2 of the light receiving element 23 in the y direction to the operational amplifier circuits 80 and 8, respectively.
Input to the inverting input terminal of 1. Here, the operational amplifier circuits 80 and 81 form a current-voltage conversion circuit having a feedback resistor 82, a feedback capacitor 83, a feedback resistor 84, and a feedback capacitor 85, respectively, while grounding their non-inverting input terminals, respectively, and thereby an output signal. S _y1-1 and S _y1-2 are converted into current and voltage and output.

The operational amplifier circuit 86 includes input resistors 87 and 8
8. An adder circuit is formed together with the feedback resistor 89, and the output signals of the operational amplifier circuits 80 and 81 are added and output. The operational amplifier circuit 90 forms a subtraction circuit together with the input resistors 91 and 92, the feedback resistor 93, and the ground resistor 94, and the operational amplifier circuit 8
Subtraction processing is executed between the output signals 0 and 81, and the processing result is output. The division circuit 95 uses the operational amplification circuit 90.
Output signal is divided by the output signal of the operational amplifier circuit 86 and output, and the processing result is output.

Similarly, the operational amplifier circuits 96 and 97 are
A non-inverting input terminal is grounded, and a current-voltage conversion circuit having a feedback resistor 98, a feedback capacitor 99, a feedback resistor 100, and a feedback capacitor 101 is formed, and the output signals S _y2-1 and S _y2-2 are _{thereby generated} . Converts current and voltage and outputs.

The operational amplifier circuit 102 forms an adder circuit together with the input resistors 103 and 104 and the feedback resistor 105, adds the output signals of the operational amplifier circuits 96 and 97, and outputs them. The operational amplifier circuit 106 includes input resistors 107, 108,
A subtraction circuit is formed together with the feedback resistor 109 and the grounding resistor 110, a subtraction process is executed between the output signals of the operational amplifier circuits 96 and 97, and the processing result is output.

The division circuit 115 has the operational amplifier circuit 1
The output signal of 06 is divided by the output signal of the operational amplifier circuit 102 and output, and the processing result is output. As a result, the beam divergence measuring device 20 detects the divergence angle in the y direction even for the laser beam L1 incident via the convex lenses 21 and 22.

Since the convex lenses 21 and 22 are arranged at both ends in the long axis direction of the laser beam L1, when the straight line connecting the centers of the convex lenses 21 and 22 intersects the optical axis of the laser beam L1. That is, when the optical axis of the laser beam L1 is correctly held between the convex lenses 21 and 22, the detection result of the value 0 is obtained.
As a result, the beam divergence angle measuring device 20 can output the output signals of the dividing circuits 95 and 115 via the test points T8 and T9 and confirm whether or not the optical axis is correctly held. ing.

Thus, the result of the actual measurement is represented by the symbol "*".
As shown in FIG. 6, the maximum is 0.02 [mra
The divergence angle can be detected by the error [d], and sufficient accuracy can be secured for practical use.

In the above structure, the laser beam L1 emitted from the large-diameter lens of the lens barrel 2 is received by the convex lenses 21 and 22 at both ends in the major axis direction of the laser beam L1 and serves as a position detecting element. The light is collected on the light receiving elements 23 and 24, and this causes the light receiving element 2
3 and 24, it is possible to detect the output signals S _{x1-1 to} S _y2-2 whose signal levels change according to the inclinations θ1 and θ2 of the laser beam L1 with respect to the respective convex lenses 21 and 22.

Of the output signals of the light receiving elements 23 and 24, the output signals S _x1-1 , S _x1-2 and S _x2-1 , S in the x direction are _included .
_{The x2-2} is subjected to current-voltage conversion processing in the operational amplifier circuits 32, 33, 52 and 53 forming the current-voltage converter circuits 26 and 27, and then the operational amplifier circuits 38 and 42, the division circuit 50 and the operational amplifier circuit, respectively. 58, 62 and the division circuit 70 convert the signals Vθ1 and Vθ2 representing the angles, and the operational amplification circuit 71 forming the subtraction circuit 30 detects a difference signal between the signals Vθ1 and Vθ2, thereby expanding the beam. The angle θ is detected.

According to the above configuration, the laser beam L1
The laser beam L1 is condensed by the convex lenses 21 and 22 at both ends in the major axis direction of the laser beam, and the inclination of the laser beam L1 incident on the convex lenses 21 and 22 is detected by the light receiving elements 23 and 24, and the inclination is detected. By detecting the divergence angle of the laser beam L1 based on the result,
The divergence angle of the laser beam L1 can be detected simply and accurately.

In the above embodiment, the case where the divergence angle of the laser beam L1 is simply measured has been described, but the present invention is not limited to this, and the tilt of the optical axis may be detected together. That is, the tilt detection results of the angle calculation circuits 29 and 30 can be added together to measure the tilt of the optical axis.

Further, in the above-described embodiment, the case where the divergence angle is measured only in the major axis direction of the laser beam L1 has been described, but the present invention is not limited to this, and the measurement is also performed in the minor axis direction. Good.

Further, in the above-mentioned embodiments, the case where the divergence angle of the laser beam emitted from the optical space transmission device is measured has been described, but the present invention is not limited to this, and the luminous flux emitted from various optical systems is described. It can be widely applied to the case of measuring the parallelism of.

[0065]

As described above, according to the present invention, it is possible to easily and accurately measure the divergence angle of a light beam emitted into a space or the like.

[Brief description of drawings]

FIG. 1 is a block diagram showing a beam divergence angle measuring apparatus according to an embodiment of the present invention.

FIG. 2 is a perspective view showing an arrangement of the laser beam of the optical free space transmission apparatus when the beam divergence angle measuring apparatus of FIG. 1 is used.

FIG. 3 is a schematic diagram showing the principle of tilt measurement of the beam divergence angle measuring device of FIG.

FIG. 4 is a connection diagram for explaining signal processing of the beam divergence angle measuring apparatus of FIG.

FIG. 5 is a connection diagram for explaining the signal processing in the y direction shown corresponding to FIG.

FIG. 6 is a characteristic curve diagram showing a measurement result of the beam divergence angle measuring apparatus of FIG.

FIG. 7 is a schematic diagram showing an optical space transmission device.

[Explanation of symbols]

 1 Optical Space Transmission Device 7 Large Diameter Lens 20 Beam Divergence Measurement Device 21, 22 Convex Lens 23, 24 Light-Receiving Element 26, 27 Current-Voltage Conversion Circuit 28, 29 Angle Calculation Circuit 30 Subtraction Circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical indication H04B 10/22

Claims (2)

[Claims] 1. At both ends of a light beam in a direction transverse to the optical axis,
Based on the first and second angle detection results, first and second angle detection systems that respectively detect the angle of the light flux with respect to the optical axis and output first and second angle detection results, A beam divergence angle measuring device, comprising: a divergence angle detection system for detecting a divergence angle of the entire light flux. 2. The first and second angle detection systems include a lens system that receives and focuses the light flux at both ends of the light flux, and receives the focused light flux and condenses the light flux. A light receiving element that outputs a position detection signal whose signal level changes according to the position, and a signal processing circuit that outputs the first and second angle detection results based on the position detection signal, respectively. The beam divergence angle measuring device according to claim 1.