JPS6342726B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rotational displacement detection device that obtains the direction and magnitude of rotation using electrical signals.

The present invention makes use of the inertia of a liquid so that an ultrasonic pulse emitted into a stationary liquid is reflected by several ultrasonic reflecting plates placed in the liquid and passes through a specific location in time and space. an ultrasonic liquid cell made of
It consists of a Fourier optical system that detects ultrasonic pulses inside the cell from outside the cell. FIG. 1 is a perspective view showing the concept of the present invention, and shows a vibrator 2 that emits ultrasonic pulses into the interior of an ultrasonic liquid cell 1, two reflecting plates 3a that reflect the ultrasonic pulses, 3b is shown. Lenses 5 and 6 are fitted into the upper and lower surfaces of the cell in order to pass the parallel light beam from the laser light source 8 into the cell and form an image at the center of the detection filter 4. An optical filter 7 having three rectangular apertures is arranged parallel to these two lens surfaces. The Fourier transform optical system for ultrasonic pulse detection is composed of the laser light source 8, the magnifying lens 9, the lenses 5 and 6, the detection filter 4, and the photoelectric converter 10. Next, the structure of the ultrasonic liquid cell 1 and the arrangement of the detection filter 4 and the vibrator will be explained. FIG. 2 shows the internal state of the cell 1 with the top lid 11 removed. The vibrator 2 is fixed to the cell wall and emits ultrasonic pulses at an angle of 30 degrees toward the center of the cell. This ultrasonic pulse is applied to the reflecting plates 3a and 3b arranged toward the center of the cell.
It is reflected twice at a reflection angle of 60 degrees, and some of it is reflected directly and some of it is further reflected on the transducer surface, and then absorbed by the ultrasonic absorbing material 12 and disappears. As is clear from the figure, the optical filters 7 are arranged from the center of the cell.
The apertures are arranged radially at an angle of 120°, and their long sides are perpendicular to the direction of ultrasound propagation. Therefore, due to the ultrasonic waves emitted from the vibrator 2. At each of the three opening positions of the optical filter 7, an optical phase grating in which the liquid density changes in a grid pattern appears. This method of detecting an optical phase grating using ultrasonic waves will be explained next. FIG. 3 shows the optical filter 7.
The opening position of the detection filter 4 and the relative position of the detection opening of the detection filter 4 are shown. As shown in FIG. 1, these two filters are arranged at the center of the optical axis, and the x-axis and the α-axis are spatially parallel, and the y-axis and the β-axis are parallel to each other. Now, when the ultrasonic pulse 16 crosses one aperture 13a of the optical filter 7 in FIG. 3, the light beam passing through this aperture is diffracted by the optical phase grating generated in the liquid. , and is further focused by a lens 6 to form an image at the position of the detection filter 4.
In the present invention, the traveling direction of the ultrasonic pulse across the aperture 13a is in the short side direction of the aperture as shown in FIG. Based on Hofer's theory of diffraction, the shaded areas a,
Appears in a′. Similarly, an ultrasonic pulse passing across the aperture 13b causes the aperture 13 to
Due to c, diffracted light is generated at locations c and c'. When the ultrasonic pulse 16 repeats reflection in the liquid cell and goes around once, if the liquid in the cell and the optical filter 7 are in a stationary state, the distance between the transducer 2 and the reflection plates 3a and 3b is reflected. and appears on the detection filter with a specific period determined by the ultrasonic propagation velocity v. In the present invention, in order to detect the periodic occurrence of this diffraction image bright spot, the detection filter 4 is provided with six circular apertures corresponding to the apertures of the optical filter 7. FIG. 4 is a diagram showing that when the liquid cell 1 undergoes a rotational movement at an angle θ after the ultrasonic pulse 16 is emitted, the generation cycle of the above-mentioned diffraction image bright spots changes. Assuming that the rotational motion of the cell is of a magnitude and speed that does not significantly disturb the inertial quiescence of the liquid within the cell, the ultrasonic pulse 16 emitted into the liquid will be spatially fixed. The vehicle travels along a specific course at a speed v. When the cell starts rotating after the ultrasonic pulse 16 crosses the aperture 13a, the time taken for the ultrasonic pulse 16 to cross the aperture 13b changes compared to when it is in a stationary state. If this time difference is expressed as d and the distance between the aperture center of the optical filter 7 and the cell center is expressed as R, then d≈Rtanθ/v
Obtain an approximate formula for . When θ is small, tanθ≒kθ
(k: constant of proportionality), d≒kRθ/v.
In the case of the optical filter 7 having three apertures as in the present invention, the optical output due to diffraction can be obtained three times for one ultrasonic pulse, and the time difference d indicating the rotation angle θ can be obtained twice. . Therefore, by setting the repetition time of the ultrasonic pulse appropriately, it is possible to obtain periodic optical output pulses, and by electrically measuring changes in the generation interval of these pulses, the rotation angle θ degrees or the rotation time can be determined. A change θ _T [o/s] can be obtained. However, in continuous operation using periodic ultrasound pulses, it must be taken into account that the spatial period of the ultrasound pulses in the liquid changes due to the Doppler effect due to the displacement of the transducer. FIG. 5 is a diagram illustrating the operating principle of the present invention in consideration of the Doppler effect due to displacement of the vibrator. Figure a shows the rotational change of the liquid cell, and figure b shows the ultrasonic position in the cell corrected to a straight line position ignoring reflections. The locations indicated by dotted lines are the positions when the liquid cell is in a stationary state. Figure c shows the apertures of the optical filter 7 arranged in a straight line as in figure b. In this figure, instead of the ultrasonic pulse shown in figure b moving, the aperture shown in figure c moves in the order of 1, 2, . . . , 17 in the right direction of the figure. In addition, the temporal correspondence between the ultrasonic pulse and the aperture position is
The relative position of P ₁ and opening 1 is determined as time t=0.
The movement of the apertures is a combination of ultrasonic propagation and rotation of the liquid cell, and the center trajectories of the three apertures are as shown by the bold lines in Figure c. Opening positions 1, 5, 9, 13, and 17 indicated by diagonal lines indicate the opening positions when ultrasonic pulses are emitted, and since no ultrasonic pulses exist within the liquid cell, no optical output appears. The optical output pulse becomes a triangular pulse when the spatial length of the ultrasonic pulse is made to match the short side of the aperture according to the principle of spatial cross-correlation calculation. The result of converting this into an electrical signal by the photoelectric converter 10 is shown in d of the same figure. The black dot above the pulse indicates the position of the output pulse when the liquid cell is stationary. As is clear from Figure d, the three pulse trains of ultrasonic pulses P ₁ to _{P 4} show an overall shift due to the Doppler effect and a change in the time difference d due to the rotation of the liquid cell. In order to extract the time difference d from this pulse position change, it is necessary to clearly separate the three sets of output pulses sequentially generated by the same ultrasonic pulse as shown in this figure. therefore,
The spatial minimum repetition period of the ultrasonic pulse needs to be four times or more the aperture center distance. Next, we will describe an example of an electrical method for detecting the time ratio of the rotational change shown in Figure a from the three pulse trains thus obtained. FIG. 6 is a time chart of this method, and FIG. 6a is an enlarged view of FIG. 5d. The upper T mark indicates the output pulse position when the liquid cell is in a stationary state, d indicates the time change due to the rotation of the cell, and g indicates a part of the time change due to the Doppler effect of the vibrator 2. Figure b shows the output of a monostable multivibrator triggered by the output pulse of figure a, and the dashed line number 19 shows the average value of the output rectangular pulses in the liquid cell stationary state. This phase-modulated output rectangular pulse is demodulated into an analog signal, and the signal shown by the dotted line is the signal shown by the dotted line. Further, this demodulated signal is detected at time t ₁ with m ₁ being the maximum value in the interval from time t ₀ to t ₁ . Similarly, the section maximum values m ₂ to ₄ are detected at times t ₂ to ₄ , respectively. Figure c shows the interval maximum value m ₀ obtained in figure b.
₄ is a diagram showing that 4 is held for a period of time ( _t0 to _t1 ), ( _t1 to _t2 )...( _t4 to _t5 ), respectively. In this way, a signal that digitally changes with the repetition period of the ultrasonic pulse is obtained. This signal value can be determined by setting the operating constants of the monostable multivibrator, demodulator, and maximum value holding circuit to appropriate values in consideration of the repetition period of the ultrasonic pulse. can be approximated to. However, in the above case, since the section maximum value m is held for each period of the ultrasonic pulse, the signal detection time is delayed by one period with respect to the start of rotation of the liquid cell. In Figure c, the rotational change of the liquid cell in consideration of this time delay is shown by a dotted line. This time delay is
Since the ultrasonic pulse period is short, there is no problem in practical use. The above method is an example of typical signal detection, and there are also more accurate detection methods such as the pulse counting method and the phase comparison method that uses the ultrasonic pulse applied to the transducer 2 as a reference signal. is possible. FIG. 7 is a block diagram of an embodiment of the present invention. For the purpose of downsizing the device, the optical system is bent using two reflecting mirrors 15a and 15b, and an electric circuit device 14 for signal detection and a vibrator excitation device 2 are used.
The structure is a combination of 0 and 0.

The present invention has the above configuration, and has the effect of being able to detect rotational changes of the liquid cell about the cylindrical center axis at high speed and continuously using electrical signals. In addition, by appropriately selecting the viscosity and density of the liquid in the cell, it is possible to set the cut-off characteristic for low-speed rotation, that is, the range of undetectable low-speed rotation, so that only high-speed minute rotation (vibration) during low-speed steady rotation can be set. It has a detectable effect. Furthermore, the present invention basically detects output signals due to rotation around the optical axis, and by arranging a liquid stabilizer made of a material that transmits light in the liquid cell, it is possible to detect signals other than the detection rotation surface. It has the potential to eliminate signals caused by rotation and vibration.

[Brief explanation of drawings]

Fig. 1 is a sketch of the liquid cell and optical system showing the concept of the present invention, Fig. 2 is a drawing showing the internal structure of the liquid cell, Fig. 3 is a drawing showing the opening positions of the optical filter and detection filter, and Fig. 4 is a diagram showing the opening positions of the optical filter and detection filter. The figure shows the displacement of the output pulse due to rotational movement, the figure 5 shows the operation timing chart, the figure 6 shows the timing chart in the electrical processing of the output pulse, and the figure 7 shows the example. . 1 is a liquid cell, 2 is a vibrator, 3a and 3b are reflection plates, 4 is a detection filter, 5 and 6 are lenses, 7,
7' is an optical filter, 8 is a laser light source, 9 is a magnifying lens, 10 is a photoelectric converter, 11 is a liquid cell top lid, 12 is an ultrasonic absorption material, 13a, 13b,
13c is an opening, 14 is a detection electric circuit device, 15
a, 15b indicate a reflecting mirror, 16 indicates an ultrasonic pulse signal, 17 indicates a liquid substance, 18 indicates the order number of the optical filter shown in FIG. 5c, 19 indicates the average value of the pulse signal, 20 is a oscillator excitation device.

Claims (1)

[Scope of Claims] 1. A laser light source 8 that generates a parallel light beam; A liquid containing cell 1 that holds a liquid substance in a cylinder having an axis parallel to the light beam; an ultrasonic transducer 2 that generates ultrasonic pulses at right angles to the axis; and an ultrasonic transducer 2 that is provided in the cell 1 and reflects the ultrasonic waves emitted from the transducer 2 substantially at right angles to the light beam and directs it toward the axis. a plurality of reflecting plates 3 that are circulated around the circular beam; and n (n1) windows that transmit a portion of the parallel light flux that is phase-modulated or phase-modulated by the circular ultrasonic waves; Laser light source 8
Optical filter 7 arranged on the side or the opposite side
and a lens 6 that Fourier-transforms the light flux passing through the n windows to form an image; and a lens 6 that is arranged on the imaging plane of the lens 6 and allows the first-order diffracted light due to the ultrasonic wave that has passed through the n windows to pass through. a detection filter 4 having a plurality of apertures; a photoelectric converter 10 that receives the diffracted light that has passed through the apertures and converts it into signals of a group of n electrical pulses; A rotational displacement detection device comprising a rotation detection device that detects rotation of a cell. 2 a laser light source 8 that generates a parallel light beam; a liquid storage cell 1 that holds a liquid substance in a cylinder having an axis parallel to the light beam; an ultrasonic transducer 2 that generates a sound wave pulse; a plurality of ultrasonic transducers provided in the cell 1 that reflect the ultrasonic wave emitted from the transducer 2 at right angles to the light beam and circulate it around the axis; a reflecting plate 3; having n (n1) windows that transmit a portion of the parallel light flux that is phase-modulated or phase-modulated by the circulating ultrasound; Laser light source 8
Optical filter 7 arranged on the side or the opposite side
and a lens 6 that Fourier-transforms the light flux passing through the n windows to form an image; and a lens 6 that is arranged on the imaging plane of the lens 6 and allows the first-order diffracted light due to the ultrasonic wave that has passed through the n windows to pass through. a detection filter 4 having a plurality of apertures; a photoelectric converter 10 that receives the diffracted light that has passed through the apertures and converts it into signals of a group of n electric pulses; one ultrasonic pulse passes through the n windows; an excitation device 20 that excites the transducer so as to generate the next ultrasonic pulse at a predetermined time after all the ultrasonic pulses have been traversed; A rotation detection device that continuously detects the rotational displacement of the cell 1 by detecting the rotation of the cell 1 within the predetermined time period during which the pulse crosses n windows.