Optical gyroscope, rotation direction detection method, and program

Abstract

This provides a compact optical gyroscope with a shorter optical path length. [Solution] An optical gyroscope comprising: a light source that generates and outputs pulsed laser light; an optical separator that separates the laser light output by the light source into two different directions; a first photodetector positioned such that a light-receiving surface is located in the direction of propagation of one laser beam, and the angle between the direction of propagation of the one laser beam and the light-receiving surface is a first arrangement angle; a second photodetector positioned such that a light-receiving surface is located in the direction of propagation of the other laser light, and the angle between the direction of propagation of the other laser light and the light-receiving surface is a second arrangement angle different from the first arrangement angle; and a detection device that detects the direction of rotation based on the electrical pulse waveform output by the first photodetector upon receiving the laser light and the electrical pulse waveform output by the second photodetector upon receiving the laser light.

Description

Technical Field

[0001] The present disclosure relates to an optical gyroscope, a method for detecting a rotation direction, and a program.

Background Art

[0002] FIG. 13 is a block diagram showing the configuration of an optical fiber gyroscope 100, which is an example of an optical gyroscope. In the optical fiber gyroscope 100, a beam splitter 102 separates the laser light irradiated by a light source 101 into two laser lights, and makes the two separated laser lights enter both ends of an optical fiber 103 wound in a coil shape. The laser light incident from one end propagates clockwise in the optical fiber 103, and the laser light incident from the other end propagates counterclockwise in the optical fiber 103. After propagation, the two laser lights exiting from the end opposite to the incident end reach a photodetector 104 via the beam splitter 102 and are received by the photodetector 104.

[0003] The two laser lights propagate in the same optical fiber 103. Therefore, when the device including the optical fiber gyroscope 100 is stationary, the phases of the two laser lights detected by the photodetector 104 are in the same phase. On the other hand, when the device including the optical fiber gyroscope 100 rotates clockwise, due to the Sagnac effect, the optical path length of the laser light advancing clockwise becomes longer, and the optical path length of the laser light advancing counterclockwise becomes shorter. Conversely, when the device rotates counterclockwise, the optical path length of the laser light advancing counterclockwise becomes longer, and the optical path length of the laser light advancing clockwise becomes shorter. Therefore, a phase difference occurs in the phases of the two laser lights detected by the photodetector 104. The rotation direction can be detected by calculating the angular velocity from the time difference corresponding to this phase difference.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] In the optical fiber gyroscope 100, a time difference corresponding to the phase difference between two laser beams, one clockwise and one counterclockwise, is used to calculate angular velocity and detect the direction of rotation. To ensure that this time difference appears with the desired resolution, an optical fiber 103 of several hundred meters in length is required. In contrast, Patent Document 1 discloses a technology that can reduce the length of the optical fiber 103 to a fraction of this length, but even with this technology applied, an optical fiber of several tens of meters in length is still required.

[0006] Gyroscopes are increasingly being installed in various devices with limited space, such as aircraft, ships, and vehicles. Therefore, there is a need for smaller optical gyroscopes with shorter optical path lengths.

[0007] The purpose of this disclosure is to provide an optical gyroscope, a method for detecting the direction of rotation, and a program that solve the above-mentioned problems. [Means for solving the problem]

[0008] An optical gyroscope according to one aspect of the present disclosure includes: a light source that generates and outputs pulsed laser light; an optical separator that separates the laser light output by the light source in two different directions; a first photodetector whose light-receiving surface is positioned in the direction of propagation of one laser beam, and the angle between the direction of propagation of the one laser beam and the light-receiving surface is a first positioning angle; a second photodetector whose light-receiving surface is positioned in the direction of propagation of the other laser light, and the angle between the direction of propagation of the other laser light and the light-receiving surface is a second positioning angle different from the first positioning angle; and a detection device that detects the direction of rotation based on the pulsed waveform of an electrical signal output by the first photodetector upon receiving the laser light and the pulsed waveform of an electrical signal output by the second photodetector upon receiving the laser light.

[0009] A rotation direction detection method according to one aspect of the present disclosure includes a light source that generates and outputs a pulsed laser beam, an optical separator that separates the laser beam output by the light source in two different directions, a first photodetector positioned such that a light-receiving surface is located in the direction of propagation of one laser beam and the angle between the light-receiving surface and the direction of propagation of the one laser beam is a first arrangement angle, receiving the one laser beam and outputting a pulsed electrical signal, a second photodetector positioned such that a light-receiving surface is located in the direction of propagation of the other laser beam and the angle between the light-receiving surface and the direction of propagation of the other laser beam is a second arrangement angle different from the first arrangement angle, receiving the other laser beam and outputting a pulsed electrical signal, and a detection device that detects the rotation direction based on the pulsed electrical signal output by the first photodetector and the pulsed electrical signal output by the second photodetector.

[0010] A program according to one aspect of the present disclosure is a program for causing the computer of an optical gyro to function as a detection means for detecting the direction of rotation based on the pulse waveform of an electrical signal output by the first photodetector upon receiving the laser light and the pulse waveform of an electrical signal output by the second photodetector upon receiving the laser light. The computer comprises a light source that generates and outputs a pulse waveform of a laser light in the form of a pulse waveform of a laser light, the first photodetector which is positioned such that the angle between the direction of travel of the first laser light and the light-receiving surface is a first positioning angle, the second photodetector which is positioned such that the angle between the direction of travel of the other laser light and the light-receiving surface is a second positioning angle different from the first positioning angle, and a computer. [Effects of the Invention]

[0011] According to one embodiment described above, a compact optical gyroscope with a shorter optical path length can be provided. [Brief explanation of the drawing]

[0012] [Figure 1] This is a block diagram showing an example of the configuration of an optical gyroscope related to this disclosure. [Figure 2] This is a diagram (part 1) illustrating the change in optical path length when the optical gyroscope relating to this disclosure rotates clockwise. [Figure 3] This is a diagram (part 2) illustrating the change in optical path length when the optical gyroscope relating to this disclosure rotates clockwise. [Figure 4] This is a schematic diagram of an example of the optical path when the optical gyroscope related to this disclosure rotates clockwise. [Figure 5] This figure illustrates the change in optical path length when the optical gyroscope relating to this disclosure rotates counterclockwise. [Figure 6] This is a schematic diagram of an example of the optical path when the optical gyroscope related to this disclosure rotates counterclockwise. [Figure 7] This flowchart shows the processing flow using the optical gyroscope detection device related to this disclosure. [Figure 8] This figure shows an example of an electrical signal pulse waveform when the optical gyroscope related to this disclosure rotates clockwise. [Figure 9] This figure shows an example of an electrical signal pulse waveform when the optical gyroscope related to this disclosure rotates counterclockwise. [Figure 10] This block diagram shows the hardware configuration of the detection device related to this disclosure. [Figure 11] This is a block diagram showing an example of the configuration of an optical gyroscope related to this disclosure. [Figure 12] This flowchart shows an example of the procedure for the rotation direction detection method related to this disclosure. [Figure 13] This block diagram shows an example configuration of a fiber optic gyroscope. [Modes for carrying out the invention]

[0013] Hereinafter, each embodiment will be described with reference to the drawings. In all the drawings, the same or corresponding components are denoted by the same reference numerals, and common descriptions are omitted.

[0014] <First Embodiment> (Configuration of Optical Gyro) FIG. 1 is a block diagram showing the configuration of an optical gyro 1 according to an embodiment of the present disclosure. The optical gyro 1 includes a light source 2, a beam splitter 3, two photodiodes (hereinafter referred to as PDs (Photo Diodes)) 4-1 and 4-2, and a detection device 5. Hereinafter, the arrangement of the light source 2, the beam splitter 3, and the PDs 4-1 and 4-2 in a state where the optical gyro 1 is stationary without rotating will be described.

[0015] The light source 2 generates and outputs laser light having a pulse waveform. Here, it is assumed that the pulse waveform generated by the light source 2 is a continuous sine wave waveform. The beam splitter 3 is arranged such that the separation surface for transmitting and reflecting is inclined at 45° with respect to the traveling direction of the laser light output from the light source 2. When the laser light output from the light source 2 enters the beam splitter 3 and reaches the separation surface, not all of the laser light passes through the separation surface, and a part of the laser light is reflected. In other words, the beam splitter 3 separates the incident laser light into two directions such that one direction is perpendicular to the traveling direction of the incident laser light and the other direction coincides with the traveling direction of the incident laser light.

[0016] Each of the PDs 4-1 and ٤-2 receives laser light on its light receiving surface and outputs an electrical signal having a magnitude corresponding to the light intensity of the received laser light. The PD 4-1 is arranged such that the angle formed by the traveling direction of one of the laser lights separated by the beam splitter 3 and the light receiving surface is a first arrangement angle (hereinafter referred to as angle θ1). Here, it is assumed that the angle θ1 is 90°. Also, the distance between the light receiving position 11 where the PD 4-1 receives the laser light on its light receiving surface and the separation position 10 where the beam splitter 3 separates the laser light on the separation surface is represented by "L".

[0017] PD4-2 is positioned such that the angle between the direction of propagation of the other laser beam separated by the beam splitter 3 and the light-receiving surface is a second positioning angle (hereinafter referred to as angle θ2) that is different from angle θ1. Furthermore, PD4-2 is positioned such that the distance between the light-receiving position 12, which receives the laser beam on the light-receiving surface, and the separation position 10 is "L". Here, angle θ2 is assumed to be an obtuse angle.

[0018] The detection device 5 stores in its internal memory information information such as the speed of the laser light generated by the light source 2, angles θ1 and θ2, and distance L, which are predetermined constants, as well as information showing mathematical formulas, which will be described later. As shown by the dashed lines, the detection device 5 is connected to each of the PD4-1 and 4-2 by electrical circuits and captures the electrical signals output by each of the PD4-1 and 4-2. The detection device 5 detects the rotation direction of the optical gyroscope 1 based on the time difference corresponding to the phase difference of the pulse waveform represented by the captured electrical signals and the information stored in its internal memory.

[0019] (Regarding changes in optical path length due to rotation) Here, we will explain the change in optical path length that occurs when the optical gyroscope 1 rotates clockwise and counterclockwise with the separation position 10 as the center of rotation.

[0020] (Regarding the change in optical path length when rotated clockwise) Figure 2 illustrates the change in optical path length at PD4-1 when the optical gyroscope 1 rotates clockwise by an angle α around the separation position 10 as the center of rotation between time tA and time tB. The dashed line PD4-1-tA represents the position of PD4-1 at time tA. The solid line PD4-1-tB represents the position of PD4-1 at time tB.

[0021] At time tA, the laser beam traveling in a straight line from separation position 10 towards PD4-1-tA continues to travel in a straight line without changing direction between time tA and time tB. In contrast, PD4-1 rotates clockwise and is located at position PD4-1-tB at time tB, so it receives the laser beam at the position indicated by the symbol 11-tB on the receiving surface. Therefore, the optical path length of the laser beam is the distance from the position indicated by the symbol 11-tA to the position indicated by the symbol 11-tB plus L. More specifically, since the angle θ1 is 90°, the distance from separation position 10 to the symbol 11-tB is "L / cos(α)". Therefore, in the case of PD4-1, when rotating clockwise, the optical path length becomes longer, as shown in the following equation (1).

[0022] L / cos(α)-L···(1)

[0023] Figure 3 illustrates the change in optical path length at PD4-2 when the optical gyroscope 1 rotates clockwise by an angle α around the separation position 10 as the center of rotation between time tA and time tB. The dashed line PD4-2-tA represents the position of PD4-2 at time tA. The solid line PD4-2-tB represents the position of PD4-2 at time tB.

[0024] At time tA, the laser beam traveling in a straight line from separation position 10 towards PD4-2-tA continues to travel in a straight line without changing direction between time tA and time tB. In contrast, PD4-2 rotates clockwise and is located at position PD4-2-tB at time tB, so it receives the laser beam at the position indicated by symbol 12-tB on the light-receiving surface. Therefore, the optical path length of the laser beam is the distance from the position indicated by symbol 12-tA to the position indicated by symbol 12-tB plus distance L.

[0025] More specifically, the optical path length of the laser beam can be calculated using the following formula. In Figure 3, a perpendicular line is drawn between the separation position 10 and the position indicated by the numeral 12-tB, passing through the position indicated by the numeral 21, which is shown by the dashed line. The position where this line segment and the perpendicular line intersect is the position indicated by the numeral 22. In this case, the distance from the separation position 10 to the position indicated by the numeral 22 is "Lcos(α)".

[0026] The distance of the dashed line segment, that is, the distance from the position indicated by sign 21 to the position indicated by sign 22, is "Lsin(α)". In Figure 3, the angle β is "180-α-θ²". Therefore, the distance from the position indicated by sign 22 to the position indicated by sign 12-tB is "Lsin(α) / tan(β)" = "Lsin(α) / tan(180-α-θ²)" = "-Lsin(α) / tan(α+θ²)". Thus, in the case of PD4-2, when rotating clockwise, the optical path length, shown in equation (2) below, becomes longer.

[0027] Lcos(α)-Lsin(α) / tan(α+θ2)-L···(2)

[0028] Here, since the angle θ2 is obtuse, the distance shown in equation (2) is longer than the distance shown in equation (1), and the difference in distance is calculated by subtracting equation (1) from equation (2), which is given by equation (3).

[0029] Lcos(α)-Lsin(α) / tan(α+θ2)-L / cos(α)...(3)

[0030] Figure 4 schematically illustrates two examples of optical paths observed when the optical gyroscope 1 rotates clockwise at a constant speed with the separation position 10 as the center of rotation. The laser beam traveling from the separation position 10 towards PD4-1 is observed to curve counterclockwise, as shown by the solid line, and reach the position indicated by symbol 11-tB, which is shifted to the left of the position indicated by symbol 11. The laser beam traveling from the separation position 10 towards PD4-2 is observed to curve counterclockwise, as shown by the solid line, and reach the position indicated by symbol 12-tB, which is shifted above the position indicated by symbol 12.

[0031] (Regarding the change in optical path length when rotating counterclockwise) Assume that the optical gyroscope 1 rotates counterclockwise by an angle γ around the separation position 10 as the center of rotation between time tC and time tD. In this case, for PD4-1, the configuration is obtained by moving PD4-1-tB to a position symmetric to the line passing through the separation position 10 and the position indicated by the symbol 11-tA in Figure 2, and then replacing "α" with "γ", "tA" with "tC", and "tB" with "tD". Therefore, in the case of PD4-1, the optical path length becomes longer, similar to the clockwise case, and the optical path length becomes longer by the length shown in the following equation (4), which is obtained by replacing "α" with "γ" in equation (1).

[0032] L / cos(γ)-L···(4)

[0033] Figure 5 illustrates the change in optical path length at PD4-2 when the optical gyroscope 1 rotates counterclockwise by an angle γ around the separation position 10 as the center of rotation between time tC and time tD. The dashed line PD4-2-tC represents the position of PD4-2 at time tC. The solid line PD4-2-tD represents the position of PD4-2 at time tD.

[0034] At time tC, the laser beam traveling in a straight line from separation position 10 towards PD4-2-tC continues to travel in a straight line without changing direction between time tC and time tD. In contrast, PD4-2 rotates counterclockwise and is located at position PD4-2-tD at time tD, so it receives the laser beam at the position indicated by symbol 12-tD on the light-receiving surface. Therefore, the optical path length of the laser beam is the distance L minus the distance from the position indicated by symbol 12-tD to the position indicated by symbol 12-tC.

[0035] More specifically, the optical path length of the laser beam can be calculated using the following formula. In Figure 5, a perpendicular line is drawn between the separation position 10 and the position indicated by reference numeral 12-tD, passing through the position indicated by reference numeral 25, which is shown by the dashed line. The position where this line segment and the perpendicular line intersect is the position indicated by reference numeral 26. In this case, the distance from the separation position 10 to the position indicated by reference numeral 26 is "Lcos(γ)".

[0036] The distance of the dashed line segment, that is, the distance from the position indicated by sign 25 to the position indicated by sign 26, is "Lsin(γ)". In Figure 5, the angle δ is "θ2-γ". Therefore, the distance from the position indicated by sign 26 to the position indicated by sign 12-tD is "Lsin(γ) / tan(δ)" = "Lsin(γ) / tan(θ2-γ)". Thus, in the case of PD4-2, when rotating counterclockwise, the optical path length, shown in equation (5) below, becomes shorter.

[0037] L-(Lcos(γ)+Lsin(γ) / tan(θ2-γ))...(5)

[0038] For PD4-1, the optical path length is longer, and for PD4-2, the optical path length is shorter. The difference in distance is calculated by adding equations (4) and (5), resulting in the following equation (6).

[0039] L / cos(γ)-Lcos(γ)-Lsin(γ) / tan(θ2-γ)...(6)

[0040] Figure 6 schematically shows the two optical paths observed when the optical gyroscope 1 rotates counterclockwise at a constant speed with the separation position 10 as the center of rotation. The laser beam traveling from the separation position 10 towards PD4-1 is observed to curve clockwise, as shown by the solid line, and reach the position indicated by symbol 11-tD, which is shifted to the right of the position indicated by symbol 11. The laser beam traveling from the separation position 10 towards PD4-2 is observed to curve clockwise, as shown by the solid line, and reach the position indicated by symbol 12-tD, which is shifted below the position indicated by symbol 12.

[0041] (Rotation direction detection process using optical gyroscope) The process of detecting the direction of rotation using the optical gyroscope 1 will be explained with reference to Figures 7 to 9. The detection device 5 acquires the electrical signals output by PD4-1 and the electrical signals output by PD4-2. The detection device 5 detects the time difference between the pulse waveform indicated by the acquired electrical signal from PD4-1 and the pulse waveform indicated by the acquired electrical signal from PD4-2 (S1).

[0042] Figure 8 shows an example of the pulse waveforms of the electrical signals of PD4-1 and PD4-2, respectively, captured by the detection device 5 when the optical gyro 1 rotates clockwise. Figure 9 shows an example of the pulse waveforms of the electrical signals of PD4-1 and PD4-2, respectively, captured by the detection device 5 when the optical gyro 1 rotates counterclockwise. In Figures 8 and 9, the waveform indicated by reference numeral 30-1 is the pulse waveform of the electrical signal of PD4-1, and the waveform indicated by reference numeral 30-2 is the pulse waveform of the electrical signal of PD4-2.

[0043] When the optical gyro 1 is rotated clockwise, as shown in Figure 8, the pulse waveform of the electrical signal of PD4-2 (indicated by reference numeral 30-2) lags behind the pulse waveform of the electrical signal of PD4-1 (indicated by reference numeral 30-1). When the optical gyro 1 is rotated counterclockwise, as shown in Figure 9, the pulse waveform of the electrical signal of PD4-2 (indicated by reference numeral 30-2) lags behind the pulse waveform of the electrical signal of PD4-1 (indicated by reference numeral 30-1).

[0044] However, the state shown in Figures 8 and 9 occurs when the optical path difference between the optical path length from the separation position 10 to the position where the laser light is received on the receiving surface of PD4-1 and the optical path length from the separation position 10 to the position where the laser light is received on the receiving surface of PD4-2, which is caused by tilting PD4-2 at an angle θ2, is less than half a wavelength of the pulse waveform. If this optical path difference is greater than half a wavelength of the pulse waveform, when rotated clockwise, it will appear as a phase lead rather than a phase lag, and when rotated counterclockwise, it will appear as a phase lag rather than a phase lag. Therefore, the range of angles θ2 that can be selected is limited by the length of the pulse waveform. To widen the selectable range of angle θ2, a pulse waveform with a longer wavelength can be used. However, if the wavelength of the pulse waveform is made too long, unless the rotation angle α and angle γ are large, a large phase difference will not appear between the pulse waveform of the electrical signal of PD4-1 (indicated by reference numeral 30-1) and the pulse waveform of the electrical signal of PD4-2 (indicated by reference numeral 30-2) in Figures 8 and 9. In other words, the longer the wavelength of the pulse waveform, the lower the rotation detection accuracy becomes. Therefore, the appropriate pulse waveform wavelength is determined based on the rotation detection accuracy required for the optical gyroscope 1 and the magnitude of angle θ2 that can be constructed when building the optical gyroscope 1.

[0045] The time difference corresponding to the phase difference shown in Figures 8 and 9 can be detected, for example, as follows: The detection device 5 detects the time t1 of any one peak in the pulse waveform of the electrical signal of PD4-1, indicated by reference numeral 30-1, and uses the detected time t1 as the reference time. The detection device 5 detects multiple peak times in the pulse waveform of the electrical signal of PD4-2, indicated by reference numeral 30-2, and selects the time closest to time t1 among the multiple detected peak times as time t2. The detection device 5 subtracts time t1 from time t2 to obtain the time difference corresponding to the phase difference.

[0046] When optical gyroscope 1 rotates clockwise, the time difference becomes a positive value indicating a phase lag, as shown in Figure 8. When optical gyroscope 1 rotates counterclockwise, the time difference becomes a negative value indicating a phase lead, as shown in Figure 9. When optical gyroscope 1 is stationary, the time difference becomes zero, indicating no phase difference.

[0047] Therefore, the detection device 5 determines whether the time difference is positive, negative, or zero (S2). If the detection device 5 determines that the time difference is positive (S2, positive), it calculates the distance difference by multiplying the speed of the laser light stored in the internal memory by the time difference (S3-1). The detection device 5 calculates the rotation angle α from the calculated distance difference based on a formula that shows the relationship between the optical path difference caused by rotation and the rotation angle when rotating clockwise, obtained by substituting the angle θ2 stored in the internal memory into the above equation (3) (S4-1).

[0048] On the other hand, if the detection device 5 determines that the time difference is negative (S2, negative), it calculates the distance difference by multiplying the speed of the laser light stored in its internal memory by the absolute value of the time difference (S3-2). The detection device 5 then calculates the rotation angle γ from the calculated distance difference based on a formula that shows the relationship between the optical path difference caused by rotation and the rotation angle when rotating counterclockwise, obtained by substituting the angle θ2 stored in its internal memory into the above formula (6) (S4-2).

[0049] The detection device 5 calculates the angular velocity by dividing the rotation angle calculated in process S4-1 or S4-2 by the time difference detected in S1 (S5). The detection device 5 determines that the rotation is clockwise if the calculated angular velocity is positive, and counterclockwise if it is negative, and outputs the calculated angular velocity along with the determination result (S6), and then terminates the process.

[0050] In the process of S2, if the detection device 5 determines that the time difference is zero (S2, zero), it outputs "no rotation direction" and "angular velocity 0" (S3-3) and terminates the process.

[0051] (Effects of the first embodiment) In the optical gyro 1 described above, PD4-1 is positioned such that the angle between the direction of propagation of one of the laser beams separated by the beam splitter 3 and the light-receiving surface is angle θ1. PD4-2 is positioned such that the angle between the direction of propagation of the other laser beam separated by the beam splitter 3 and the light-receiving surface is a different angle θ2 than angle θ1. By positioning PD4-1 and PD4-2 in this way, when the optical gyro 1 is rotated clockwise or counterclockwise, an optical path difference occurs between the optical path length from the separation position 10 to the position where the laser beam is received on the light-receiving surface of PD4-1, and the optical path length from the separation position 10 to the position where the laser beam is received on the light-receiving surface of PD4-2. Based on the phase difference of the laser beam caused by this optical path difference, the detection device 5 can detect the angular velocity and rotation direction of the optical gyro 1.

[0052] In this way, the optical gyroscope 1 is a small optical system comprising a light source 2, a beam splitter 3, and PD4-1, 4-2. By adjusting the position of PD4-1, 4-2, an optical path difference is generated when the system is rotated clockwise or counterclockwise, thus eliminating the need for long optical fibers like those in an optical fiber gyroscope. Therefore, the optical gyroscope 1 makes it possible to provide a smaller optical gyroscope with a shorter optical path length compared to an optical fiber gyroscope. This makes it possible to mount the optical gyroscope 1 on various objects with limited mounting space, such as aircraft, ships, and vehicles. Furthermore, for example, by mounting the optical gyroscope 1 on a device carried by a person, the weight of the device can be reduced, thereby reducing the burden of carrying it.

[0053] (Modification of the first embodiment) In the above embodiment, the detection device 5 detects the time difference between the peak of the pulse waveform of the electrical signal acquired from PD4-1 and the peak of the pulse waveform of the electrical signal acquired from PD4-2 as a time difference corresponding to the phase difference during processing S1. Alternatively, the detection device 5 may detect the time difference corresponding to the phase difference by calculating the cross-correlation between the pulse waveform of the electrical signal of PD4-1 and the pulse waveform of the electrical signal of PD4-2.

[0054] In the above embodiment, the light source 2 is assumed to generate laser light in the form of a continuous sinusoidal pulse waveform. However, the pulse waveform of the laser light generated by the light source 2 is not limited to a sine wave, but may be any waveform in which the light intensity increases or decreases, such as a triangular wave, square wave, or sawtooth wave, and the pulse waveform may be such that the arbitrary waveform is repeated at a constant period.

[0055] In the above-described embodiment, if angular velocity is not required and only the direction of rotation needs to be known, the detection device 5 may determine and output the direction of rotation from the result of the determination process in S1. That is, if the result of the determination process in S1 is "positive", the detection device 5 may output "clockwise" as the direction of rotation; if it is "negative", it may output "counterclockwise" as the direction of rotation; and if it is "zero", it may output "no direction of rotation".

[0056] In the above embodiment, angle θ1 is set to 90° and angle θ2 is set to an obtuse angle. However, angles θ1 and θ2 can be any angles that are greater than 0° and less than 180°, and are different angles, as long as the optical path difference caused by the difference in angles is less than half a wavelength of the pulse waveform. Note that equations (3) and (6) above are equations for when angle θ1 is 90° and angle θ2 is an obtuse angle. Therefore, depending on what angles θ1 and θ2 are selected, equations (3) and (6) will be replaced with predetermined equations corresponding to the selected angles θ1 and θ2.

[0057] In the above embodiment, when the optical gyro 1 is stationary, the distance between the receiving position 11 on the receiving surface of PD4-1 where the laser light is received and the separation position 10, and the distance between the receiving position 12 on the receiving surface of PD4-2 where the laser light is received and the separation position 10, are set to be the same distance "L". In contrast, when the optical gyro 1 is stationary, if the phase of the laser light received by PD4-1 at the receiving position 11 on the receiving surface and the phase of the laser light received by PD4-2 at the receiving position 12 on the receiving surface are the same, the distance between the receiving position 11 and the separation position 10, and the distance between the receiving position 12 and the separation position 10 may be different. This is because, if the phases are the same, even if these distances are different, the phase will advance in a clockwise direction, as shown in Figure 8, and the phase will lag in a counterclockwise direction, as shown in Figure 9. However, if these distances are different, the corresponding distance must be substituted for L in equations (3) and (6).

[0058] In the above embodiment, the light source 2 is assumed to generate laser light in the form of a continuous sinusoidal pulse waveform. In contrast, the light source 2 may, for example, generate and output pulse waveforms that are temporally isolated and do not repeat periodically at any given timing. Here, a temporally isolated state means, for example, a pulse waveform that is one period of any waveform whose light intensity increases or decreases, such as a sine wave, triangular wave, square wave, or sawtooth wave, and where, between adjacent waveforms, the light intensity remains constant for a certain period of time. In the case of a waveform such as a sine wave, it may be a half-period waveform instead of a full period waveform. Here, it is preferable that the certain period of time is such that the combination of the pulse waveform of the electrical signal of PD4-1 to be compared by the detection device 5 and the pulse waveform of the electrical signal of one PD4-2 does not overlap with other combinations on the time axis.

[0059] When using laser light with such temporally isolated pulse waveforms, it becomes unnecessary to consider the phase, as is the case with laser light with continuous sinusoidal pulse waveforms. Therefore, the condition that the optical path difference between the optical path length from the output position of the laser light source 2 to the receiving position of the laser light on the receiving surface of PD4-1 and the optical path length from the output position of the laser light source 2 to the receiving position of the laser light on the receiving surface of PD4-2 must be less than half a wavelength of the pulse waveform does not need to be applied. Consequently, the range of angles from which angle θ2 can be selected can also be widened.

[0060] In the above embodiment, laser light is received by PD4-1 and PD4-2, but a photodetector equipped with any photoelectric conversion element other than a photodiode may be used, and the size of the optical gyro 1 can be further reduced by using a smaller photodetector.

[0061] In the above embodiment, the beam splitter 3 separates the laser beam into two, with one beam traveling in a direction perpendicular to the other. Alternatively, any optical separator capable of separating the laser beam into two, other than the beam splitter, may be used, and this optical separator may be one that separates the laser beam in any two directions.

[0062] In the above embodiment, the optical gyroscope 1 is assumed to rotate around the separation position 10. However, the center of rotation of the optical gyroscope 1 does not necessarily have to coincide perfectly with the separation position 10. In this case, when the optical gyroscope 1 rotates, the position on the separation surface of the beam splitter 3 that receives the laser light from the light source 2 shifts from the separation position 10, making it impossible to calculate the angular velocity accurately. However, if the difference between the center of rotation and the separation position 10 is small, it is possible to determine whether the rotation is clockwise or counterclockwise.

[0063] <Hardware Configuration> Figure 10 shows an example of the hardware configuration of the detection device 5 shown in Figure 1 according to this disclosure. The detection device 5 according to this disclosure is a computer comprising, for example, a CPU (Central Processing Unit) 81, RAM (Random Access Memory) 82, ROM (Read Only Memory) 83, auxiliary storage device 84, interface module 85, input module 86, and output module 87. The CPU 81, RAM 82, ROM 83, auxiliary storage device 84, interface module 85, input module 86, and output module 87 are interconnected by a bus 88. The auxiliary storage device 84 is, for example, an HDD (Hard Disk Drive) or an SSD (Solid State Drive). The detection device 5 is connected to PD4-1 and PD4-2 via the interface module 85.

[0064] When the user of the detection device 5 operates the input module 86, information such as constants is recorded in the internal storage area of ​​the detection device 5, which is reserved in the auxiliary storage device 84. An application program pre-stored in the ROM 83 or the auxiliary storage device 84 is executed by the CPU 81, and the processing shown in the flowchart in Figure 7 is performed, for example. The output module 87 is, for example, a liquid crystal display, and the angular velocity and rotation direction obtained as a result of the processing in the flowchart in Figure 7 are displayed on the output module 87.

[0065] <Second Embodiment> Hereinafter, an embodiment of the present disclosure will be described with reference to the figures. As shown in Figure 11, the optical gyro 90 includes a light source 92 that generates and outputs laser light in the form of a pulse waveform, an optical separator 93 that separates the laser light output by the light source 92 into two different directions, a first photodetector 94-1 whose light-receiving surface is positioned in the direction of propagation of one laser beam and is positioned such that the angle between the direction of propagation of the one laser beam and the light-receiving surface is a first positioning angle, a second photodetector 94-2 whose light-receiving surface is positioned in the direction of propagation of the other laser beam and is positioned such that the angle between the direction of propagation of the other laser beam and the light-receiving surface is a second positioning angle different from the first positioning angle, and a detection device 95 that detects the direction of rotation based on the pulse waveform of an electrical signal output by the first photodetector 94-1 after it receives the laser light and the pulse waveform of an electrical signal output by the second photodetector 94-2 after it receives the laser light.

[0066] As shown in Figure 12, the light source 92 generates and outputs a pulsed laser beam (S91). The optical separator 93 separates the laser beam output by the light source 93 into two different directions (S92). A first photodetector 94-1, positioned with a light-receiving surface in the direction of propagation of one laser beam and such that the angle between the light-receiving surface and the direction of propagation of one laser beam is a first arrangement angle, receives the laser beam and outputs a pulsed electrical signal (S93). A second photodetector 94-2, positioned with a light-receiving surface in the direction of propagation of the other laser beam and such that the angle between the light-receiving surface and the direction of propagation of the other laser beam is a second arrangement angle different from the first arrangement angle, receives the other laser beam and outputs a pulsed electrical signal (S94). A detection device 95 detects the direction of rotation based on the pulsed electrical signal output by the first photodetector and the pulsed electrical signal output by the second photodetector (95), and terminates the process.

[0067] Although the present disclosure has been described above with reference to embodiments, the present disclosure is not limited to the embodiments described above. Various modifications to the structure and details of the present disclosure are possible, as can be understood by those skilled in the art within the scope of the present disclosure. Furthermore, each embodiment can be combined with other embodiments as appropriate.

[0068] Some or all of the embodiments described above may also be described as follows, but are not limited to the following.

[0069] (Note 1) An optical gyroscope comprising: a light source that generates and outputs pulsed laser light; an optical separator that separates the laser light output by the light source in two different directions; a first photodetector whose light-receiving surface is positioned in the direction of propagation of one laser beam, and the angle between the direction of propagation of the one laser beam and the light-receiving surface is a first positioning angle; a second photodetector whose light-receiving surface is positioned in the direction of propagation of the other laser light, and the angle between the direction of propagation of the other laser light and the light-receiving surface is a second positioning angle different from the first positioning angle; and a detection device that detects the direction of rotation based on the pulsed waveform of an electrical signal output by the first photodetector upon receiving the laser light and the pulsed waveform of an electrical signal output by the second photodetector upon receiving the laser light.

[0070] (Note 2) An optical gyroscope as described in (Note 1), which rotates about the position in the optical separator where the laser light is separated.

[0071] (Note 3) The optical gyroscope described in (Note 1) or (Note 2), wherein either the first arrangement angle or the second arrangement angle is 90°.

[0072] (Note 4) The optical gyroscope described in any one of (Note 1) to (Note 3), wherein the first photodetector and the second photodetector are arranged such that the distance between the light-receiving position of the light-receiving surface of the first photodetector, which receives one of the laser beams when stationary, and the separation position in the optical separator, which separates the laser beam, and the distance between the light-receiving position of the light-receiving surface of the second photodetector, which receives the other laser beam when stationary, and the separation position are the same length.

[0073] (Note 5) The pulse waveform is a pulse waveform in which the same waveform in which the light intensity increases and decreases is repeated at a constant period, as described in any one of (Note 1) to (Note 4).

[0074] (Note 6) The pulse waveform is a pulse waveform in which the same waveform with increasing and decreasing light intensity is repeated at a constant period, and the first photodetector and the second photodetector are arranged such that the phase of the pulse waveform of the electrical signal output by the first photodetector, which receives one of the laser beams when stationary, and the phase of the pulse waveform of the electrical signal output by the second photodetector, which receives the other laser beam when stationary, are in the same phase, as described in any one of (Note 1) to (Note 3).

[0075] (Note 7) The pulse waveform is a time-isolated pulse waveform in which the light intensity increases and decreases, as described in any one of (Note 1) to (Note 4).

[0076] (Note 8) The optical gyroscope according to any one of (Note 1) to (Note 7), wherein the detection device detects the time difference between the pulse waveforms of the electrical signals output by the first photodetector and the second photodetector, and detects the direction of rotation based on the detected time difference.

[0077] (Note 9) The detection device is an optical gyroscope as described in (Note 8), which calculates angular velocity based on a formula that shows the relationship between the detected time difference, the speed of the laser light, and the optical path difference and rotation angle caused by rotation, and is determined by the direction of rotation, the first arrangement angle and the second arrangement angle.

[0078] (Note 10) A rotation direction detection method comprising: a light source that generates and outputs a pulsed laser beam; an optical separator that separates the laser beam output by the light source in two different directions; a first photodetector positioned such that a light-receiving surface is located in the direction of propagation of one laser beam, and the angle between the direction of propagation of the one laser beam and the light-receiving surface is a first arrangement angle, receiving the one laser beam and outputting a pulsed electrical signal; a second photodetector positioned such that a light-receiving surface is located in the direction of propagation of the other laser beam, and the angle between the direction of propagation of the other laser beam and the light-receiving surface is a second arrangement angle different from the first arrangement angle, receiving the other laser beam and outputting a pulsed electrical signal; and a detection device that detects the rotation direction based on the pulsed electrical signal output by the first photodetector and the pulsed electrical signal output by the second photodetector.

[0079] (Note 11) The rotation direction detection method described in (Note 10), wherein the optical separator rotates around the position where the laser light is separated.

[0080] (Note 12) The rotation direction detection method according to (Note 10) or (Note 11), wherein either the first arrangement angle or the second arrangement angle is 90°.

[0081] (Note 13) The rotation direction detection method according to any one of (Note 10) to (Note 12), wherein the first photodetector and the second photodetector are arranged such that the distance between the light-receiving position of the light-receiving surface of the first photodetector that receives one laser beam when stationary and the separation position in the optical separator that separates the laser beam, and the distance between the light-receiving position of the light-receiving surface of the second photodetector that receives the other laser beam when stationary and the separation position are the same length.

[0082] (Note 14) The rotation direction detection method according to any one of (Note 10) to (Note 13), wherein the pulse waveform is a pulse waveform in which the same waveform in which the light intensity increases and decreases is repeated at a constant period.

[0083] (Note 15) The rotation direction detection method according to any one of (Note 10) to (Note 12), wherein the pulse waveform is a pulse waveform in which the same waveform with increasing and decreasing light intensity is repeated at a constant period, and the first photodetector and the second photodetector are arranged such that the phase of the pulse waveform of the electrical signal output by the first photodetector, which receives one of the laser beams when stationary, and the phase of the pulse waveform of the electrical signal output by the second photodetector, which receives the other laser beam when stationary, are in the same phase.

[0084] (Note 16) The rotation direction detection method according to any one of (Note 10) to (Note 13), wherein the pulse waveform is a time-isolated pulse waveform in which the light intensity increases or decreases.

[0085] (Note 17) The rotation direction detection method according to any one of (Note 10) to (Note 16), wherein the detection device detects the time difference between the pulse waveforms of the electrical signals output by the first photodetector and the second photodetector, and detects the rotation direction based on the detected time difference.

[0086] (Note 18) The rotation direction detection method described in (Note 17), wherein the detection device calculates the angular velocity based on a formula that shows the relationship between the time difference to be detected, the speed of the laser light, and the optical path difference and rotation angle caused by the rotation, and is determined by the rotation direction, the first arrangement angle and the second arrangement angle.

[0087] (Note 19) A program for causing the computer of an optical gyro to function as a detection means for detecting the direction of rotation based on the pulse waveform of an electrical signal output by the first photodetector upon receiving the laser light and the pulse waveform of an electrical signal output by the second photodetector upon receiving the laser light. The computer comprises a light source that generates and outputs a pulse waveform of a laser light in the form of a pulse wave; an optical separator that separates the laser light output by the light source in two different directions; a first photodetector whose light-receiving surface is positioned in the direction of propagation of one laser light, and the angle between the light-receiving surface and the direction of propagation of the one laser light is a first arrangement angle; a computer.

[0088] (Note 20) The program described in (Note 19) which rotates around the position in the optical separator where the laser light is separated.

[0089] (Note 21) The program described in (Note 19) or (Note 20), wherein either the first arrangement angle or the second arrangement angle is 90°.

[0090] (Note 22) The program described in any one of (Note 19) to (Note 21), wherein the first photodetector and the second photodetector are arranged such that the distance between the light-receiving position of the light-receiving surface of the first photodetector, which receives one of the laser beams when stationary, and the separation position in the optical separator that separates the laser beams, and the distance between the light-receiving position of the light-receiving surface of the second photodetector, which receives the other laser beam when stationary, and the separation position are the same length.

[0091] (Note 23) The pulse waveform is a pulse waveform in which the same waveform in which the light intensity increases and decreases is repeated at a constant period, as described in any one of (Note 19) to (Note 22).

[0092] (Note 24) The pulse waveform is a pulse waveform in which the same waveform with increasing and decreasing light intensity is repeated at a constant period, and the first photodetector and the second photodetector are arranged such that the phase of the pulse waveform of the electrical signal output by the first photodetector, which receives one of the laser beams when stationary, and the phase of the pulse waveform of the electrical signal output by the second photodetector, which receives the other laser beam when stationary, are in the same phase, as described in any one of (Note 19) to (Note 21).

[0093] (Note 25) The pulse waveform is a time-isolated pulse waveform in which the light intensity increases or decreases, as described in any one of (Note 19) to (Note 22).

[0094] (Note 26) The detection means is a program according to any one of (Note 19) to (Note 25) that detects the time difference between the pulse waveforms of the electrical signals output by the first photodetector and the second photodetector, and detects the direction of rotation based on the detected time difference.

[0095] (Note 27) The detection means is the program described in (Note 26), which calculates the angular velocity based on a formula that shows the relationship between the detected time difference, the speed of the laser light, and the optical path difference and rotation angle caused by the rotation, and is determined by the direction of rotation, the first arrangement angle and the second arrangement angle. [Explanation of symbols]

[0096] 1. Optical gyroscope 2 light source 3-beam splitter 4-1, 4-2 PD 5. Detection device

Claims

1. A light source that generates and outputs pulsed laser light, A light separator that separates the laser light output by the aforementioned light source into two different directions, A first photodetector is positioned such that a light-receiving surface is located in the direction of propagation of one laser beam, and the angle between the direction of propagation of the one laser beam and the light-receiving surface is a first arrangement angle. A second photodetector is positioned such that a light-receiving surface is positioned in the direction of propagation of the other laser beam, and the angle between the direction of propagation of the other laser beam and the light-receiving surface is a second arrangement angle different from the first arrangement angle. A detection device for detecting the direction of rotation based on the pulse waveform of an electrical signal output by the first photodetector upon receiving the laser light and the pulse waveform of an electrical signal output by the second photodetector upon receiving the laser light, An optical gyroscope equipped with [a specific feature].

2. The optical separator rotates around the position where the laser light is separated. The optical gyroscope according to claim 1.

3. Either the first arrangement angle or the second arrangement angle is 90°. The optical gyroscope according to claim 1.

4. The first photodetector and the second photodetector are, The distance between the light-receiving position of the light-receiving surface of the first photodetector that receives the one laser beam when stationary and the separation position in the optical separator that separates the laser beam, When stationary, the distance between the light-receiving position of the light-receiving surface of the second photodetector that receives the other laser light and the separation position is the same length. The optical gyroscope according to claim 1.

5. The pulse waveform is a pulse waveform in which the same waveform, with increasing and decreasing light intensity, is repeated at a constant period. The optical gyroscope according to claim 1.

6. The aforementioned pulse waveform is a time-isolated pulse waveform in which the light intensity increases and decreases. The optical gyroscope according to claim 1.

7. The detection device is The time difference between the pulse waveforms of the electrical signals output by the first photodetector and the second photodetector is detected, and the rotation direction is detected based on the detected time difference. The optical gyroscope according to claim 1.

8. The detection device is A formula showing the relationship between the detected time difference, the speed of the laser light, and the optical path difference and rotation angle caused by rotation, wherein the angular velocity is calculated based on a formula determined by the direction of rotation, the first arrangement angle, and the second arrangement angle. The optical gyroscope according to claim 7.

9. The light source generates and outputs laser light in a pulsed waveform. The optical separator separates the laser light output by the light source into two different directions. A first photodetector is positioned such that a light-receiving surface is located in the direction of propagation of one laser beam, and the angle between the direction of propagation of the one laser beam and the light-receiving surface is a first arrangement angle. The first photodetector receives the one laser beam and outputs a pulse waveform of an electrical signal. A second photodetector is positioned such that a light-receiving surface is located in the direction of propagation of the other laser beam, and the angle between the direction of propagation of the other laser beam and the light-receiving surface is a second arrangement angle different from the first arrangement angle. The second photodetector receives the other laser beam and outputs a pulse waveform of an electrical signal. The detection device detects the direction of rotation based on the pulse waveform of the electrical signal output by the first photodetector and the pulse waveform of the electrical signal output by the second photodetector. Method for detecting the direction of rotation.

10. A light source that generates and outputs pulsed laser light, A light separator that separates the laser light output by the aforementioned light source into two different directions, A first photodetector is positioned such that a light-receiving surface is located in the direction of propagation of one laser beam, and the angle between the direction of propagation of the one laser beam and the light-receiving surface is a first arrangement angle. The computer of the optical gyroscope comprises a second photodetector, the second photodetector being positioned such that the light-receiving surface is located in the direction of propagation of the other laser beam, and the angle between the direction of propagation of the other laser beam and the light-receiving surface is a second arrangement angle different from the first arrangement angle, and a computer. Detection means for detecting the direction of rotation based on the pulse waveform of an electrical signal output by the first photodetector upon receiving the laser light and the pulse waveform of an electrical signal output by the second photodetector upon receiving the laser light. A program designed to function as such.

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