JPS6222134B2 - - Google Patents

Description

[Detailed Description of the Invention] This invention provides time axis compression and
This invention relates to an acousto-optic electrical signal processor that performs decompression, time delay, and signal sampling.

Conventionally, several methods have been considered for compressing/expanding and delaying the time axis of analog electrical signals. The first method is to temporarily store electrical signals using a digital memory and control the readout speed. Devices based on this method are highly versatile and can be expected to have high accuracy, but they require a large number of storage elements to ensure the waveform accuracy of analog signals, and they require analog-to-digital (A-
D) and a D-A converter. therefore,
The device has a complicated configuration and is expensive. next,
There is a method using signal transfer delay elements such as CCD and BBD, but this method also requires a large number of elements and complicated electric circuits in order to obtain good waveform accuracy.
The method using a surface acoustic wave element is also similar to the above example, and the compression/expansion rate of the time axis and the delay time cannot be easily varied. Furthermore, there is a method of recording analog signals on a magnetic tape or the like and controlling the playback speed, but this method has problems with mechanical operation and operating time.

As described above, it is very difficult to perform time-base processing of analog signals using an electrical circuit.

The present invention uses an acousto-optic spatial signal processing technique for electrical signal time axis processing, converts an analog electrical signal into an ultrasound signal, spatially temporarily stores it, and uses light after an appropriate delay time. An object of the present invention is to provide an acousto-optic electrical signal processor for detecting an ultrasonic signal from a lever and performing electrical signal time axis processing by controlling the detection time and detection position.

According to the invention, an analog electrical signal is applied to an ultrasound transducer placed within the acousto-optic cell filled with an ultrasound propagation medium, such as a liquid, and is radiated into the cell as an ultrasound signal. This ultrasonic signal spatially retains the information of the analog electrical signal until it reaches and is absorbed by an ultrasonic absorbing member disposed opposite to the ultrasonic transducer surface. At this time, the time axis of the analog electrical signal corresponds to the spatial axis in the propagation direction of the ultrasound signal. To read out the information held spatially, the positional coordinates of the spatial axis are specified using a dedicated ultrasonic beam, and the information is detected using light. That is, when a narrow ultrasonic beam is emitted to the spatial position to be detected while irradiating the entire ultrasonic signal representing the analog electrical signal with plane wave light, the plane wave light that passes through the area where the two ultrasonic waves overlap A special phase change occurs. This phase change can be converted into a light amount change using one lens, and this light amount change is proportional to the square of the amplitude value of the analog electrical signal. Further, the ultrasonic beam for specifying position coordinates can be emitted to any position on the intra-cell spatial axis of the ultrasonic signal, that is, the time axis corresponding to the analog electrical signal. Therefore, by scanning the spatial axis with the ultrasonic beam, a time-axis processed signal of the analog electrical signal can be obtained in the form of an optical signal.

FIG. 1 is a block diagram of an embodiment of an acousto-optic cell for electrical signal processing, which is one of the components of the present invention. A sinusoidal electric signal having a resonant frequency of the first vibrator 2 is amplitude-modulated with an analog electric signal to be processed and applied to the first vibrator 2. This amplitude modulation signal is converted into an ultrasonic signal by the first transducer 2 and radiated into an ultrasonic propagation medium 10 such as a liquid. Plane wave light is incident into the acousto-optic cell 5 through light transmission windows 1a and 1b perpendicular to the propagation direction of the ultrasound signal. Further, an ultrasonic beam dedicated to specifying position coordinates is emitted from the second transducer 3 perpendicular to the traveling direction of this plane wave light. FIG. 2 shows the shape of the acousto-optic cell 5 when viewed from the light traveling direction. The first vibrator 2 and the second vibrator 3 are provided with input terminals 8a and 8b, respectively, to which electrical signals are applied.

FIG. 3 shows the relationship between the ultrasound signal 11 and the ultrasound beam 12 inside the acousto-optic cell 5. As shown in FIG. A sinusoidal signal of frequency ₁ amplitude-modulated by the analog electrical signal 13 of FIG. is fired as. It is known that this ultrasonic signal 11 causes a lattice-like density change in the ultrasonic propagation medium 10 in the cell, and that the magnitude of the density change is approximately proportional to the amplitude of the analog electrical signal 13 when the ultrasonic amplitude is small. It is being In addition, this lattice-like density change forms a one-dimensional phase grating with a lattice constant of (v/ ₁ ), where the sound speed in the cell is v, and when plane wave light is passed through this phase grating, the optical wavefront A phase change corresponding to the amplitude modulated sine wave signal is generated. This correspondence relationship is x=vt, where t is the time axis of the sinusoidal amplitude modulation signal and x is the spatial axis in the ultrasound propagation direction within the cell.

Next, at a position a distance Ld away from the first transducer 2 in the x direction, the second transducer 3 transmits a signal perpendicular to the traveling direction of the plane wave light so as to intersect with the ultrasonic signal 11. The ultrasonic beam 12 is emitted. The traveling direction axis of this ultrasonic beam 12 is y
shall be. Although the x and y axes do not necessarily need to be perpendicular to each other, the figure shows a case where the x and y axes are perpendicular to each other. The ultrasonic beam 12 is generated by applying a constant amplitude sinusoidal signal of frequency f ₂ to the input terminal 8b of the second transducer 3. Similar to the ultrasound signal 11, this ultrasound beam 12 forms a one-dimensional phase grating in the y-axis direction within the cell. The ultrasound beam 12 and the ultrasound signal 11
A two-dimensional phase grating in the x and y axis directions is formed at the intersection of the two. The plane wave light that has passed through this two-dimensional phase grating undergoes a two-dimensional phase change, but since the ultrasonic beam intensity is constant, the amount of phase change can only be varied by the analog electrical signal 13 applied to the terminal 8a. amount. therefore,
The light that has passed through the two-dimensional phase grating has the amplitude value information of the shaded area of the analog electric signal 13 shown in FIG. It is held as

Here, consider that the second vibrator 3 located at the position Ld is continuously excited to emit an ultrasonic beam that does not change over time. In this case, the ultrasonic signal 11 currently overlapping with the ultrasonic beam has amplitude information of an analog electrical signal applied to the first transducer 2 (Ld/v) hours before the current time. be.
Therefore, by optically detecting the ultrasonic signals 11 in this overlapping portion using the properties of a two-dimensional phase grating, it is possible to obtain a (Ld/v) time-delayed signal of the analog electrical signal 13. .

FIG. 4 is a block diagram of an embodiment of the acousto-optic electrical signal processor of the present invention. The plane wave light that has passed through the acousto-optic cell 5 for electrical signal processing and has been phase-modulated by the ultrasound signal 11 and the ultrasound beam 12 is filtered by a spatial optical filter 7 by a lens 6.
The image is formed on the surface of This image is a so-called two-dimensional Fourier transform image or a two-dimensional diffraction image, and is a two-dimensional spectrum representing a phase change distribution in a plane perpendicular to the optical axis of plane wave light. In the figure, consider the case where the ultrasonic beam 12 is emitted upward perpendicularly to the plane of the paper from the second transducer 3 at the shaded position. FIG. 5 shows the relationship between the shapes and relative positions of the acousto-optic cell 5 and the spatial optical filter 7 as viewed from the optical axis direction. The coordinate axes of the plane of the spatial optical filter 7, which are spatially parallel to the x and y axes indicating the traveling directions of the ultrasonic signals 11 and 12 in the acousto-optic cell 5, are α and β, respectively. shall be. The first-order diffraction bright spot due to the sinusoidal ultrasound generated by the time-frequency electrical signal in the acousto-optic cell is located on the surface of the spatial optical filter 7, where the light source wavelength is λ and the focal length of the lens 6 is F. On the top, two points appear symmetrically with respect to the optical axis at a distance d=λFf/v from the optical axis. The direction of these diffraction bright spots with respect to the optical axis point is equal to the ultrasound traveling direction. Therefore, the positions of the first-order diffracted light spots generated by the ultrasonic signal 11 are the points P ⁺ (a, o) and P ^- (-a, o) shown in FIG. However, a=λF ₁ /v. Similarly, the positions of the first-order diffracted light spots of the ultrasonic beam 12 created by the sinusoidal electric signal of frequency ₂ are Q ⁺ (o ₁ b) and Q ^- (o ₁ - b) shown in Figure b. . however,
b=λF ₂ /v. Furthermore, ultrasonic signal 1
The two-dimensional diffraction bright spot due to the intersection of 1 and the ultrasound beam 12 is the bright spot of P ⁺ , ^- diffracted at a distance ±b in the β axis direction, or the bright spot of Q ⁺ , ^- is diffracted at a distance of a
It is considered that the light is diffracted over a distance of ±a in the axial direction, and appears at four points indicated by R (±a, ±b).
Therefore, if the light from one or more of these four points passes through and is detected by the spatial optical filter 7, amplitude information of the analog electrical signal delayed by (Ld/v) time can be obtained. Since the amplitude intensity of the output light that has passed through the filter 7 is proportional to the amplitude value of the ultrasonic signal 11, that is, the analog electrical signal 13, by photoelectrically converting this, the analog signal 1
A signal delayed by 3 is obtained as an electrical signal in the form of a square value.

FIG. 6 shows a case where a single pulse ultrasonic beam is emitted and analog electrical signals are sampled. The duration of the pulsed ultrasound 14 is the length Wy of the light transmission windows 1a and 1b in the y-axis direction, and the width in the x-axis direction is p. Figure a shows how two ultrasonic waves overlap by fixing the position of the ultrasonic signal 11 and moving the pulsed ultrasonic wave 14 relative to this. Figure b shows the sampling output signal 15 after detecting a two-dimensional phase grating using two ultrasonic waves and photoelectrically converting the detected two-dimensional phase grating. However, in order to correspond to the analog electrical signal 13, the sampling output signal 15 is square compressed. The time Ts required for a pulsed ultrasonic wave of length Wy to cross the light transmission windows 1a, 1b is Ts = 2Wy/v, and since the ultrasonic pulse 14 has entered the frame of the light transmission windows 1a, 1b, The time required for the ultrasonic signal to overlap with the ultrasonic signal at point A in the same figure is Ts/2. The output signal corresponding to point aA in the figure is point b′A in the figure, and the amplitude value at this point represents the sampling value. Immediately after one pulsed ultrasound 14 finishes passing through the light transmission windows 1a, 1b, the next pulsed ultrasound is emitted from the same transducer, and by continuing to repeat this operation,
It is possible to obtain periodic sampling values as shown by the broken line in FIG. If this operation is performed using the same second vibrator 3, the sampling period for the analog electrical signal 13 and the period of the point indicating the sampling value of the sampling output signal 15 (for example, point bA' in the figure) will match. , the operation is simply sampling the delayed signal. Furthermore, if the emission period of the pulsed ultrasound 14 is constant and the position Ld of the pulsed ultrasound 14 is changed using the second transducer 3 located at a different location, the sampling period for the analog electrical signal 13 will change. , the time axis of the sampling output signal 15 is the time axis of the analog electrical signal 13 expanded or compressed. That is, if the pulsed ultrasound 14 is moved in the direction of decreasing Ld, the sampling period for the analog electrical signal 13 will be longer than Ts, and the sampling output signal 15 displayed at the period of Ts will be longer than the analog electrical signal 13. The time axis is compressed. For the same reason, if 14 pulses of pulsed ultrasound are moved in the direction of increasing Ld,
Time axis extension can be performed.

The present invention has the above configuration, and by controlling the position and timing of the ultrasonic beam emitted into the acousto-optic cell, signal processing such as delay, sampling, time axis compression/expansion, etc. of analog electrical signals can be performed. It has the effect of being possible.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of an acousto-optic cell which is a component of the present invention, FIG. 2 is a diagram of the acousto-optic cell viewed from the optical axis direction, and FIG. 3 is a diagram showing the inside of the acousto-optic cell. Figure 4 is a diagram showing the state of ultrasonic waves, Figure 4 is a diagram showing an embodiment of the present invention, Figure 5 is a diagram showing the generation position of diffracted light due to two ultrasound waves, and Figure 6 is a diagram showing the state of intersection of two ultrasound waves. and a diagram showing signal output. 1a and 1b are light transmission windows, 2 is a first vibrator, 3
is a second vibrator, 4a and 4b are ultrasonic absorbing members,
5 is an acousto-optic cell, 6 is a lens, 7 is a spatial optical filter, 8a, 8b are input terminals, 9 is a photoelectric converter, 10 is an ultrasound propagation medium, 11 is an ultrasound signal, 12 is an ultrasound beam, 13 is an analog electrical signal, 14 is a pulsed ultrasound, 15 is a sampling output signal, A is the intersection position of two ultrasound waves, A' is A
Indicates the sampling value corresponding to .

Claims (1)

[Claims] 1 An acousto-optic cell for electrical signal processing filled with an ultrasonic propagation medium, with light transmission windows 1 provided on both opposing walls of the cell and allowing plane wave light to pass through.
a, 1b; one or more first transducers 2 that convert the electrical signal to be processed into a first ultrasonic wave and radiate it into the medium perpendicular to the optical axis of the plane wave beam; It is placed a predetermined distance from the transducer in the radial direction, receives a control signal for electrical signal processing, converts it into a second ultrasonic wave, and generates a second ultrasonic wave perpendicular to the optical axis and intersects with the first ultrasonic wave. one or more second oscillators 3 that radiate into the medium so as to radiate into the medium; provided opposite to the first and second oscillators to absorb the first and second ultrasonic waves, respectively; an acousto-optic cell 5 for electrical signal processing, comprising an ultrasonic absorption member 4; a lens 6 for focusing the plane wave light beam transmitted through the cell; a spatial optical filter 7 for detecting a point, the predetermined position being related to the carrier frequency of the electrical signal to be processed consisting of an amplitude modulated wave and the radiation direction of the first and second ultrasonic waves with respect to the optical axis. The time at which the bright spot appears is determined in relation to the propagation time of the first ultrasonic wave to the intersection position, and the brightness of the bright spot is determined in relation to the propagation time of the first ultrasonic wave to the intersection position. An acousto-optic electrical signal processor characterized in that the signal is determined in relation to amplitude.