JPH04151504A - Detecting device for relative angle - Google Patents

Abstract

PURPOSE:To conduct regulation only by a part on one side and thereby to simplify the regulation by a method wherein a parallel light flux emitted from a light source is made to fall at a large incident angle on the light-sensing surfaces of photoelectric detecting elements located inside the light flux. CONSTITUTION:A parallel light flux 4 is emitted from a light source 3 fixed on a first reference part 1, while a photoelectric detector 5 made up of photoelectric detecting elements 51 and 52 is fixed on a second reference part 2. The light flux 4 falls on the elements 51 and 52 at a large incident angle. An angle formed by a light-sensing surface and the incident light flux is denoted by alpha and the angle alpha is set at an appropriate value. When alpha is changed in a minute amount in the vicinity of the value, an output of the detector 5 changes. By detecting the change in the output of the detector 5, accordingly, a change in a relative angle is determined. When alpha is set at the appropriate value, the change in the angle in the vicinity thereof is proportional to a difference between outputs of the two elements 51 and 52. When the value of alpha is small and approximate to zero, therefore, the sensitivity is increased and, besides, the output itself turns small. The precision in detection is improved consequently. As stated above, it is needed only to emit the light flux 4 toward the part 2, and regulation can be executed only by the part 2.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a relative angle detection device that precisely measures relative directional fluctuations between objects located far apart. The present invention also relates to a device used for calibrating the direction between an inertial reference device composed of an accelerometer and an artificial satellite antenna or a astronomical meridian image.

[Conventional technology] Conventionally, devices for performing more precise measurements must be installed in one central location, but due to structural constraints, etc., this has not been possible and the devices have been installed in separate locations. There are cases. In such a case, each measuring device is placed on a reference stand and is fixed, and variations in the relative distance between the stands will affect measurement accuracy.

One such example is an artificial satellite observation vessel. As shown in Fig. 12, this observation vessel is equipped with an inertial reference system (INS) 112 consisting of a gyroscope and an accelerometer, an antenna 111 for satellite tracking, and a meridian image (not shown) for astronomical measurements. We are prepared. The inertial reference device 112 constantly detects the position of the ship, but since the detection accuracy decreases due to accumulation of errors, it is necessary to calibrate it by satellite observation or astronomical measurement as appropriate. Or, conversely, there may be cases where it is necessary to precisely confirm the position of the artificial satellite using the inertial reference device 112.

Due to the arrangement on the observation ship, the inertial reference device 112, the antenna 111, and the meridian image cannot be installed at the same position, but are installed at distant positions, for example, 30 mm apart.

Each device is mounted on solid platforms 1g and 2g, but the relative position of the platforms varies depending on the rigidity of the ship. This variation is affected by weather conditions, and in particular, variations in the direction of the platform greatly affect observation accuracy, so it is necessary to precisely measure the changes in the direction of the platform and correct the observation results.

Conventionally, therefore, fluctuations in the relative angle have been detected using a device as shown in FIG. In FIG. 13, the light source unit 3h and the photoelectric position converter 121, which serve as angular references, are fixed to, for example, an antenna stand, and the reflection mirror 122 is fixed to an inertial reference device stand. A laser beam is normally used as the light source 3h, but it is not limited to a laser as long as it is collimated light, and the mirror may be a prism.The photoelectric position converter 1
Reference numeral 21 uses a COD, a four-part light receiving element, a position sensor, etc.

When initially setting the gyroscope, the mirror 122 is tilted by θ with respect to the light beam, and the light beam reflected at an angle of 2θ is set so that it hits the center of the photoelectric position converter 1216.Normally, the light beam is free from external influences. To avoid interference, the intermediate optical path section is in a pipe supported at both ends by flexible sections. Therefore, the optical path cannot be made very large, and the photoelectric position converter 121 is placed adjacent to the light source 3h to make θ as small as possible.

At this time, if the relative direction of the table on which the device is mounted changes by Δθ within the plane of FIG. 13, the angle of the mirror with respect to the light flux also changes by Δθ
The light flux changes to θ+Δθ, and the reflection direction of the light flux changes by 2Δθ to 2(θ+Δθ). If the distance between the photoelectric position converter 121 and the mirror 122 is l, then the photoelectric position converter 121
The positional change ΔP of the luminous flux above is expressed by the following equation.

Δp=f(sin2(θ◆Δθ)−sin2θl:=2
1-Δθ...(1) Therefore, the position change Δ of the light flux on the photoelectric position converter 121
If P is detected, the direction change Δθ can be found.

However, the direction change that can be detected here is only the direction change within two orthogonal planes containing the light beam, and the direction change within the plane perpendicular to the light beam cannot be detected. Conventionally, fluctuations in this direction have not been measured because they are small.

[Problem to be solved by the invention]

As shown in FIG. 13, a light source 3h, a photoelectric position converter 121
Since both have a certain size, the passing range of the light beam on the way needs to have a certain size, which is a constraint on the arrangement.

Furthermore, the light source and photoelectric position converter 121 and the mirror 122 are separated by, for example, 30 mm, each having an adjustment point, and it takes time to mutually adjust the parts separated by this distance. , accuracy is also difficult to obtain.

Further, the angle of incidence with respect to the photoelectric position converter 121 is 2θ, and when θ increases to a certain extent, correction for this angle becomes necessary.

Also, as mentioned above, it is not possible to detect a change in direction within a plane perpendicular to the light beam, making this method insufficient as a measurement method.

The present invention has been made in view of the above-mentioned problems, and it is possible to perform adjustment only on one side of a device for detecting the relative angle between separate reference portions whose directions can vary without enlarging the optical path. The purpose is to simplify the adjustment.

[Means to solve the problem]

FIG. 1 is a principle diagram showing the basic principle of the present invention. 1st
A parallel beam of light 4 is emitted from a light source 3 fixed to a reference portion 1 of. The second reference portion 2 includes a photoelectric detection element 51.
, 52 is fixed. The photoelectric detector 5 detects inside the parallel light beam 4 emitted from the light source 3,
The photoelectric detection elements 51 and 52 are installed so that the light beam is incident on the light receiving surfaces at a large angle of incidence.

The photoelectric detection elements 51 and 52 have almost the same characteristics,
The angle of incidence with respect to the parallel light beam 4 is also set to be approximately the same. 6 is a processing section that detects the difference in output from each photoelectric detection element.

[For production]

In FIG. 1, the parallel light beam 4 passes through the photoelectric detection elements 51°
incident at a large angle of incidence. Let the angle between the light-receiving surface and the incident light beam be α. Here, if there is no reflection etc. on the light receiving surface, and the light receiving surface has an area of A and a -like sensitivity, the output of the photoelectric detector 5 is a function of α, and if it is I(α), I(α) is expressed by the following equation.

I(a)=kAs1nα-(2) where k is a predetermined constant.

Also, the photoelectric detection element 51 when the angle α changes by Δα,
The change Δ■(α) in the output of 52 is expressed by the following equation, which is obtained by differentiating equation (2) with respect to α.

ΔI (a) = k AcosaΔa
-(3) From equation (3), the sensitivity to angle change is eO8α
It is expressed as

Therefore, if α is set to an appropriate value and α is changed by a minute amount around that value, the output of the photoelectric detector 5 will change. Therefore, if the fluctuation in the output of the photoelectric detector 5 is detected, the change in relative angle can be determined using equation (3).

However, in order to accurately detect changes in the relative angle, it is necessary to capture minute fluctuations in the output, making it difficult to obtain high accuracy.
1 and 52 to face the parallel light beam 4 so that they have almost the same angle of incidence. Then, the respective outputs of the photoelectric detection elements 51 and 52 change in opposite directions with respect to changes in relative angle, and are expressed as in the following equation. Here I, and I
2 is the output of each of the photoelectric detection elements 51 and 52.

ΔI I((Z)=k Acosα・ΔαΔtz(α
)= kAcosα・Δα ... (4) Δα=
(Δr, (α)−ΔI2(α))/2kAcosα・・
(5) From equation (5), it can be seen that if α is set to an appropriate value, the angle change in the vicinity is proportional to the difference in the outputs of the two photoelectric detection elements 51 and 52. If the value of α is small and close to zero, the value of cos α will be approximately 1, and the sensitivity will increase. Furthermore, since the output itself is smaller than in equation (2), the detection accuracy is improved. Further, the output difference can be detected with high accuracy by using a differential amplifier in the processing section 6, and the value of α is set in consideration of the influence of reflection on the light receiving surface. In any case, the photoelectric detection element 51
, 52, it is possible to detect a change in the angle of incidence of the parallel light beam 4 and the photoelectric detector 5, that is, a change in the direction of the reference portions 1 and 2 to which they are fixed.

As described above, the light source 3 fixed to the reference part 1 simply emits the collimated parallel light beam 4 toward the reference part 2, and there is no need for adjustment with the part on the reference part 2.
Adjustments can be made only on the reference part 2. Furthermore, the optical path is only for the parallel light beam.

〔Example〕

The device shown in Figure 1 was able to detect only changes in direction perpendicular to the plane of the paper, but if the photoelectric detector is also installed in a direction rotated 90 degrees, changes in direction perpendicular to the plane of the paper, including the optical axis of the parallel light beam, can be detected. Changes in direction can also be detected. Only the photoelectric detector portion of this embodiment is shown in FIG.

In the following figures, the same parts are represented by the same numbers and alphabets.

In FIG. 2, 4a is a parallel light beam. 51a to 5
Each of the photoelectric detection elements 4a has the same characteristics and is attached to the sensor unit 50 so as to have the same incident angle with respect to the parallel light beam 4a. 51d and 52a and 53a and 54a are set as a pair, and the difference in output is determined, and the directional fluctuation in two planes including the optical axis of the parallel light beam is detected.

The light source 3 may be anything that emits a collimated parallel light beam 4, but it is preferable to use a laser beam such as a He-Ne laser if possible.

The sensor unit 50 is a member for stably holding the four photoelectric detection elements 51a to 54a, and the set angles of the photoelectric detection elements 51a to 54a need to be held accurately because they affect detection accuracy. . In addition, in order to reduce the influence of reflection from the sensor unit 50 itself and reflection from the light receiving surface,
Surface treatment and shape are taken into consideration.

That is, the light-receiving surfaces of the photoelectric detection elements 51a to 54a are coated with an anti-reflection coating that is effective against the incident angle and wavelength of the parallel light beam. Reflection on the light-receiving surface reduces the amount of light received by itself, and the reflected light enters other light-receiving elements, causing errors, and therefore requires highly accurate anti-reflection measures.

Moreover, it is desirable that the parallel light beam 4a has a −-like light amount distribution if possible. This is because the difference in output between the photoelectric detection elements is detected, so if the intensity of light differs depending on the position within the light beam, it will cause an error.0 Normally, a laser beam has a light intensity distribution close to a normal distribution. Therefore, in order to obtain a light intensity distribution similar to that of the laser beam, it is conceivable to perform correction using a density filter having characteristics opposite to the light intensity distribution of the laser beam.

However, it is not easy to obtain a parallel light beam with a similar light intensity distribution due to diffraction during the optical path, and there is also a problem in terms of cost.

FIG. 3 shows an embodiment in which the light quantity distribution of the parallel light beam 4 is made into a normal distribution and this is electrically corrected.

FIG. 3 shows an example in which changes in only two-dimensional directions are detected to simplify the explanation. As shown in FIG. 3, the parallel light beam 4b has a normal light intensity distribution, and the zero peripheral portion is blocked by the aperture of the entrance. 51b, 52
b, 55b, and 56b are photoelectric detection elements. 6
b is a processing section, which includes amplifiers 63b to 66 that vary the amplification factor of the output from each photoelectric detection element according to an external control signal.
b, differential amplifiers 61b and 62b that output the difference between the respective outputs of amplifiers 63b and 64b and 65b and 66b; adder 69b that adds the outputs of differential amplifiers 61b and 62b and outputs the result as a differential output; amplifier 63b; and 64b, and adders 67b and 68 that add the outputs of 65b and 66b.
b. Furthermore, a corrector 70b receives the outputs of the adders 67b and 68b, calculates the output change in response to a change in the position of the photoelectric detection element within the light beam 4b, and changes the amplification factor of each amplifier 63b to 66b. .

Next, the operation of this embodiment will be explained. Each photoelectric detection element 51
b, 52b, 55b, 56b have the same shape,
Even if they are made to have the same characteristics, they will not produce the same output because the intensity of the incident light differs. Therefore, at the time of initial setting, the luminous flux 4b and the photoelectric detection elements 51b, 52b, 5
After aligning the positions of amplifiers 5b and 56b, the amplification factors of each amplifier are adjusted so that the outputs of amplifiers 63b to 66b are equal.

As described above, when the direction of the light beam 4b changes, a difference occurs in the output between the photoelectric detection elements 51b and 52b, and 55b and 56b. Differential amplifiers 61b and 62 detect the output difference.
b is 0 In this embodiment, in order to further improve accuracy, an adder 69b is provided to average the outputs of the differential amplifiers 61b and 62b, and this output becomes a differential output indicating a change in direction.

In this embodiment, further amplifiers 63b and 64b, 65b and 6
adders 67b and 6 which detect the sum of the respective outputs of 6b;
It is equipped with 8b. This output is input to the corrector 70b. At the initial setting, the photoelectric detection element 5 detects the light beam 4b.
Since 1b and 52b and 55b and 56b are adjusted symmetrically, the outputs of adders 67b and 68b are equal.

However, when the relative position of the light beam 4b and the photoelectric detection element changes, the output of each photoelectric detection element changes, and the adder 67b
There is also a difference between the outputs of 68b and 68b. Since the intensity of the light beam 4b has a normal distribution, this output difference corresponds to the positional shift of the light beam. The corrector 70b determines the positional deviation of the light beam from this output difference, and changes the amplification factor of each amplifier. This eliminates errors caused by output changes due to positional deviations of the light beam. Of course, due to the direction change of the light beam 4b, the photoelectric detection element 51b
.

Since the positions of 52b, 55b, and 56b within the luminous flux also change, errors associated with this are also removed.

Although the corrector 70b can be configured using a circuit using a differential amplifier, in this embodiment, it is configured using a microcomputer. FIG. 4 shows the configuration. This circuit uses a microcomputer (MCU) 1, similar to a circuit using a normal microcomputer.
20, ROM121, and ROM121. This circuit further includes two A/D converters 12 which receive the outputs from 67b and 68b and convert them into digital data.
3, 124, and D/A converters 125-128 for setting the amplification factors of amplifiers 63b-66b, respectively.

FIG. 5 shows the microcomputer 120 of the corrector 70b.
3 is a flowchart showing the flow of operations.

The operation will be explained according to the flowchart.

In step 131, the outputs of adders 67b and 68b are A/D
The data is captured in the form of digital data through converters 123 and 124. As mentioned above, this data is based on the light receiving element 51b, assuming that the intensity within the light beam is normally distributed.

It represents the deviation from the initial setting of the luminous flux for 52b, 55b, and 56b. Therefore, in step 132,
The positional deviation of the light flux is determined from the output ratio of the adders 67b and 68b. In step 133, the position of each light-receiving element within the light beam is calculated from this positional deviation, and in step 134, the amplifier 6 is used to eliminate the output difference of each light-receiving element due to the difference in position within the light beam.
Find the amplification factors of 3b to 66b. Then in step 135 D
/A converters 125 to 128 are set to values corresponding to the amplification factors. The amplifiers 63b to 66b are composed of a multiplier circuit that combines an operational amplifier and a channel resistance that changes depending on the voltage between the gate and source of an FET, for example.
The values set in the /A converters 125 to 128 are converted from current to voltage, and become the voltage between the gate and source described above.

This makes it possible to set the amplification factors of the amplifiers 63b to 66b in accordance with the calculation results. The microcomputer 120 performs the operations shown in FIG. 5 before measurement.

In the embodiment of FIG. 3, amplifiers 63b and 6 are used as differential outputs.
The output difference between 4J65b and 66b was averaged, but the amplifier 64
The output difference between b and 65b may be directly used as a differential output.

In this case, it is sufficient that symmetrical outputs are generated from the amplifiers 63b and 64b, and 65b and 66b, so basically there is no need to adjust the amplification factor. , it is also possible to accurately detect a change in direction by correcting the output difference between the amplifiers 64b and 65b.

Furthermore, in the embodiment shown in FIG. 3, the amplification factors of the amplifiers 63b to 66b may be fixed, and the corrector 70b may detect the positional deviation of the light beam 4b and correct the differential amplifiers 61b and 62b.

Although the embodiment shown in FIG. 3 shows a case in which changes in one direction are detected, changes in the other direction can also be detected if a similar device is provided in a direction perpendicular to the plane of the paper.

In the embodiment shown in Fig. 3, a device is described in which a plurality of photoelectric detectors for direction change detection are provided and the output difference due to fluctuations in the relative position of the light flux and the photoelectric detector is corrected. An example in which an auxiliary photoelectric detector is separately provided is shown in FIG.

In the embodiment shown in FIG. 6, in addition to the photoelectric detection elements 51c to 54c for detecting a change in the direction of the light beam 4c, auxiliary photoelectric detection elements 81c to 84c are provided for detecting the position within the light beam. Since the auxiliary photoelectric detection elements 81c to 84c have light-receiving surfaces almost perpendicular to the light beam 4c, the output does not change drastically depending on the direction change of the light beam 4c.Therefore, in the same way as shown in FIG. , an auxiliary photoelectric detection element 8 is installed in the processing section.
A correction section is provided to detect the position within the light beam 4c from the output difference between 1c and 82c, and 83c and 84c. Then, according to this positional deviation, correction is performed in the same manner as in the embodiment shown in FIG.

As mentioned above, a problem with the conventional method is that rotation of the light beam in a plane perpendicular to the optical axis cannot be detected. Therefore, in the present invention, the polarization of light is utilized to enable detection of rotation in this direction. An example of this is shown in FIG.

In FIG. 7, 91d is a linearly polarizing filter that converts the light beam 4d into linearly polarized light. If the light source 3d is a linearly polarized laser beam, the polarizing filter 91d is not necessary. 92
d is a filter that passes only a certain wavelength range, and is a bandpass filter for removing the influence of disturbance light. An interference filter is suitable for this purpose. Reference numeral 93d denotes a linearly polarizing filter, and as the polarization direction of this linearly polarizing filter changes with respect to the light beam 4d, the amount of transmitted light changes. Although there are Nicol prisms and the like as linear polarizing filters, a polarizer with a thin film coating is suitable in terms of performance. 51
d and 52d are photoelectric detection elements, and as described above, based on the output difference, the processing section 6d detects a change in the direction of the light flux, and also detects a change in the amount of received light due to a change in the polarization direction.

The operation of the embodiment shown in FIG. 7 will be explained. The polarizing filter 93d is fixed to the reference portion 2d, and the polarizing filter 93d is fixed to the reference portion 1d.
When rotational change occurs in and 2d within a plane perpendicular to the optical axis of the light beam 4d, the polarization directions of the light beam 4d and the linear polarizing filter 93d change, and the amount of transmitted light changes. Photoelectric detection elements 51d and 52
The output sum of the outputs of d is calculated by the adder 71d of the processing section 6d. This output sum is proportional to the amount of transmitted light, and from this, the change in the polarization direction of the linearly polarizing filter 93d and the light beam 4d, that is, the change in the direction in the plane perpendicular to the optical axis of the light beam 4d of the reference portions 1d and 2d can be determined. . In the processing section 6d, a differential amplifier 61d detects changes in the luminous flux in two other directions based on the output difference between the photoelectric detectors 51d and 52d. At this time, the output of the adder 71d is used to correct the change in the total amount of light to the differential amplifier 61d.

In any case, this allows changes in all directions to be detected. Regarding the change in the amount of light due to the polarization direction of the linearly polarizing filter 93d and the light beam 4d, the amount of transmitted light E(β) is expressed by the following equation, where β is the difference between the polarization directions.

E(β)=cosβ−(6), that is, reaches a maximum when β=0°, and becomes almost zero when β=90°. The rate of change is expressed by the following equation by differentiating equation (6) with respect to β.

ΔE(β)−k 1sinβ・Δβ−(7)
If β is set to a certain value according to equation (7), the change in the polarization direction in the vicinity can be found by measuring the change in the total amount of light.

Equation (7) shows that it is best to set β near 90° to increase the detection sensitivity. However, when β becomes near 90', the total amount of transmitted light is small and not enough light is incident on the photoelectric detector. , it is necessary to set the detection sensitivity and light amount in consideration.

All the examples so far have been described in which the photoelectric detectors face the light beam at approximately the same angle of incidence, but as shown in FIG. There are also examples of combinations of 59e and 59e. In this case, it is not possible to create a differential between opposing elements as in the past; for example, in FIG.
Processing is performed such as calculating the output difference between 7e and 586, and the output difference between 596 and half of the sum of the outputs of 57e and 586 on the other side.

As mentioned above, the sensitivity varies depending on the angle of incidence of the light beam on the light-receiving surface of the photoelectric detection element, but as the angle of incidence increases, the range of change that can be measured becomes smaller, so it is possible to combine different angles of incidence as shown in Fig. By installing multiple elements and switching the element set according to the measurement range, it is possible to maintain measurement performance while maintaining measurement performance.
Measurement range can be expanded.

In the description of the embodiments so far, the relative angle detection device of the present invention has been described, and in the following description, an example in which the present detection device is used will be described. As an example of application, an example of an artificial satellite observation ship has already been described in the section on conventional technology, and another example of application is shown in FIG. This is aircraft 10
This is an example in which a flying object 102 is attached to the tip portion of a wing 101 of a flying object.

The flying object 102 includes means for transporting objects for observation, missiles, and the like. These flying objects 102 are equipped with their own inertial reference devices. And at the time of separation, aircraft 1
The inertial reference device of the flying object 102 is initialized based on the data of the inertial reference device of 00.

However, the wing 101 vibrates greatly during flight due to the influence of wind pressure, etc., and this vibration causes an error in the initial value, causing the problem that the flying object 102 does not fly normally. Therefore, the relative angle detection device of the present invention is used to detect the relative angle between the inertial reference device of the aircraft 100 and the tip reference portion 105 of the wing 101 to which the flying object 102 is fixed. By correcting the initial settings based on this detection result, it is possible to improve the accuracy of the inertial reference device of the flying object 102.

Note that 104 is an optical path, which may be provided inside the blade.

Further, other application examples will be explained. FIG. 11 is a diagram showing an example of this application, and is an example of application related to initial setting of an inertial reference device of a ship. In the inertial reference device of a ship, it is necessary to set relative angles of three axes called pitch, roll, and yaw with respect to navigation coordinates. Conventionally, the inertial reference device was set in a highly sensitive state called self-alignment mode to detect gravity and the Earth's rotational angular velocity. However, since the ship itself was shaking, measurements were taken many times and averaged to eliminate the effects of shaking.

However, in order to perform highly accurate settings, it is necessary to increase the number of samplings, and several hours are required for this initial setting.

Therefore, as shown in FIG. 11, the light emitting section 31 of the present invention is installed on the quay 106. Of course, the light emitting section 31 is set at a predetermined angle with respect to the navigation coordinates. An inertial reference device 1031 of the ship 107 is installed inside, and the light receiving section 50i of the present invention is attached to this inertial reference device. The light beam from the light emitting section 31 passes through the light shielding cover 1041 and reaches the light receiving section 50i inside the ship 107. Light receiving section 50
At i, the relative angle with respect to the light beam, that is, the relative angle with respect to the navigation coordinates, is instantaneously detected. This can significantly shorten initial setup time. This is possible because there is only one light beam and the relative angle can be detected only on the light receiving section side.

〔Effect of the invention〕

As explained above, according to the present invention, changes in the relative angle of distant parts can be measured using a single optical path, which increases the degree of freedom in design and allows adjustment during installation and setting to be performed only on one side. Therefore, the effect of simplifying the adjustment can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a principle diagram showing the basic principle of the present invention. FIG. 2 is a configuration diagram showing the arrangement of photoelectric detectors for detecting changes in two directions. FIG. 3 is a configuration diagram showing an embodiment in which the number of photoelectric detectors is further increased and the influence of uneven light intensity distribution within the light beam is corrected by the output of each element. FIG. 4 is a diagram showing an example of the configuration of the corrector in the embodiment of FIG. 3 when a microcomputer is used. FIG. 5 is a flowchart showing the operation of the corrector shown in FIG. 4. FIG. 6 is a principle diagram showing an example in which an auxiliary photoelectric detector is provided to correct the influence of uneven light intensity distribution within the light beam. FIG. 7 is a configuration diagram showing an example of measuring a change in direction of a light beam in a plane perpendicular to the optical axis using a linear polarization filter. FIG. 8 is a configuration diagram showing an example of arrangement when there are three photoelectric detectors. FIG. 9 is a principle diagram showing an example of combining photoelectric detectors with different incident angles. FIG. 10 is a configuration diagram showing an application to a case where a flying object having another inertial reference device is attached to an aircraft. FIG. 11 is a diagram showing an example in which the present invention is applied to initial setting of an inertial reference device for a ship. Figure 12 is a side view of the satellite observation ship. FIG. 13 is a principle diagram showing a conventional method for measuring direction change. In the figure, 1...first reference part, 2...second reference part, 3
...Light source, 4...Light flux, 51, 52
, 53, 54, 55, 56... photoelectric detection element,
6... Processing unit, 81c, 82c, 83c, 84c... Auxiliary photoelectric detection element, 91d, 93d... Linear polarization filter, 92d... Bandpass filter.

Claims (1)

[Claims] 1. A parallel beam of light directed toward a second reference portion (2) that is fixed to a first reference portion (1) and can vary with respect to the first reference portion (1) due to external factors. (4) Means of emitting (3)
, a plurality of photoelectric detection means (51) fixed to the second reference part (2), the light receiving surfaces of which are arranged within the parallel beam (4) at substantially the same incident angle with respect to the optical axis of the parallel beam (4); , 52), and processing means (6) for receiving the outputs of the plurality of photoelectric detection means (51, 52) and detecting the output difference between the photoelectric detection means (51, 52), A relative angle detection device configured to detect a change in relative angle between a portion (1) and the second reference portion (2). 2. The processing means (6) includes photoelectric detection means (51b, 52
Further, based on the outputs of the photoelectric detection means (51b, 52b, 55b, 56b), the variation in the output of the photoelectric detection means (51b, 52b, 55b, 56b) due to the position in the parallel light beam (4) where the light amount distribution is uneven is corrected. The relative angle detection device according to claim 1, further comprising a correction means for performing the correction. 3. Furthermore, a plurality of auxiliary detection means (81c, 82c, 83c
, 84c) are provided in the parallel light beam (4c) in close proximity to the photoelectric detection means (51c, 52c, 53c, 54c), and the processing means (6) includes a plurality of auxiliary photoelectric detection means. Means (81
c, 82c, 83c, 84c), correction of fluctuations in the output of the photoelectric detection means (51c, 52c, 53c, 54c) due to the position in the parallel light beam (4c) where the light amount distribution is non-uniform. The relative angle detection device according to claim 1, further comprising a correction means for performing the following. 4. The parallel light beam (4d) is a linearly polarized parallel light beam, and the polarizing filter (93d) is connected to the photoelectric detection means (51d,
52d), the processing section (6d) is further provided with a plurality of photoelectric detection means (51d,
Based on the sum of the outputs of the parallel light beams (4d), a change in the light amount of the parallel light beams (4d) due to a change in the polarization direction of the polarizing filter (93d) is further detected. The first reference portion (1d
) and the second reference portion (2d).