JPS6351570B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an acousto-optic electrical signal processor that performs time delay, time axis expansion and compression of electrical signals, and extraction of specific interval (time) signals.

2. Description of the Related Art Conventionally, there have been acousto-optic signal processing devices that perform real-time processing of electrical signals, such as spatial real-time integration and Fourier transformation, using lens systems, ultrasonic light modulators, and the like. The present invention focuses on the time delay and temporary memory characteristics of the acousto-optic signal processing unit (ultrasonic light modulator, Fourier transform optical system, spatial filter) used in these devices, and uses this to Conventionally, analog signal delay circuits and real-time time axis expansion/compression circuits, which required extremely complex circuits and numerous electrical components, were constructed using an acousto-optic system to provide simple time delay and time axis expansion. The present invention aims to provide a signal processor for a compressor.

For this purpose, the present invention includes a transducer that converts an electrical signal to be processed into an ultrasonic wave, and a transducer for a detection ultrasonic signal that detects the electrical signal converted into an ultrasonic wave while compressing it in time. are arranged spatially facing each other with good parallelism or in the same direction, and constitute an optical ultrasound signal processing cell in which several liquid substances with different ultrasound propagation velocities are separated by a transparent partition plate as ultrasound propagation media, In addition, an optical spatial filter was provided that allows only specific output diffracted light appearing by the detection ultrasonic signal to pass through.

Next, this invention will be specifically explained with reference to the drawings.

FIG. 1 shows optical ultrasonic signal processing cells 3 and 3' which are the components of the acousto-optic electrical signal processor of the present invention.
FIG. This cell has light passing windows 5, 5' having a size sufficient for passage of band-shaped plane wave light 9,
It is composed of ultrasonic transducers 1 and 1' that emit ultrasonic waves perpendicular to the traveling direction of the plane wave light 9, and ultrasonic absorbing members 2 and 2' that absorb the ultrasonic waves emitted from the transducers. There is. In addition, there are two types of liquid substances with different propagation speeds4 as propagation media for ultrasonic waves.
It is possible to easily set a long ultrasonic propagation distance by separating the ultrasonic waves 4' with a transparent partition plate 10.
Since the two ultrasonic waves traveling in this cell are compression waves of the density of the propagation medium, a phase difference occurs partially in the band-shaped plane wave light 9 that traverses them, and when focused by a lens, a diffraction image appears.

FIG. 2 shows the optical ultrasound signal processing cells 3, 3'
This figure shows the configuration of an optical processing system that converts electrical signals into diffracted light. The laser beam 14 is expanded into band-shaped plane wave light by a lens system, passes through the cells 3 and 3', undergoes a phase change due to the ultrasonic signal in the cell, and is converged by the lens 7 and placed on the focal plane. The image is formed on eight optical spatial filters. At this time, if the ultrasonic signal exists only in the cell 3 and its frequency is a sine wave of _f1 , the diffraction image becomes a bright spot and is generated at a distance d from the optical axis point of the optical spatial filter 8. do. The direction of the diffracted light point from the optical axis point is equal to the traveling direction of the ultrasound signal, and the value of d is expressed by the following equation.

d=λFf ₁ /v ₁ ...(1) λ is the wavelength of the light source, F is the focal length of the lens 7, v ₁
is the traveling speed of the ultrasonic wave in the cell 3. Furthermore, it is known that the intensity of the diffracted light is proportional to the square of the signal amplitude when the ultrasound signal amplitude is small.

Next, consider the case where sinusoidal ultrasonic waves having different frequencies exist in the cells 3 and 3'. If these two ultrasonic waves are both perpendicular to the optical axis and their propagation directions are parallel to each other, the diffracted light will not only indicate the respective ultrasonic frequencies, but also the two frequencies that indicate the sum and difference of each frequency. Appears at the location of the point. Assuming that the respective frequencies are f ₁ and f ₂ , the distances d ⁽⁺⁾ and d ^(-) between the optical axis and the diffracted light spot are respectively expressed by the following equations, as in the case of equation (1).

v ₂ in equation (2) is the ultrasonic traveling speed within the cell 3'. Furthermore, the intensity of the diffracted light is proportional to the square of the product of two ultrasonic amplitudes, both at the sum and difference frequencies.

Based on the above, one of the two sinusoidal ultrasonic waves is amplitude-modulated with the electrical signal to be processed, and the other is amplitude-modulated with a rectangular pulse having a width less than a fraction of the minimum period of the electrical signal. Then, by detecting the sum/difference frequency diffracted light by the optical spatial filter 8 and photoelectrically converting it as shown in equation (2), time axis expansion and compression of the electrical signal can be realized.
This situation will be explained with reference to an embodiment of the present invention shown in FIG. In this embodiment, the cells 3, 3', the lens 7, and the optical spatial filter 8 are integrated in consideration of operational precision and simplicity. Band-shaped plane wave light 9 enters into the cell through a light passing window 5 provided in the cell 3. A sine wave signal of frequency f ₁ that has been amplitude-modulated by the electrical signal to be processed is applied to the electrical signal input terminal 6, converted to an ultrasound signal 11 by the ultrasound transducer 1, and transmitted inside the cell. Proceed in the direction of the arrow. The band-shaped plane wave light 9 undergoes a phase change by crossing this ultrasonic signal 11,
It is converged by the lens 7 to produce f ₁ frequency diffracted light, but this diffracted light is blocked by the optical spatial filter 8 and does not appear outside the signal processor. here,
The above-mentioned sinusoidal wave signal of frequency f ₂ is pulse-amplitude modulated and applied from the second electric signal input terminal 6' provided in the cell 3', and a pulse-like ultrasonic signal with a constant amplitude is generated in the cell. When emitted, a sum of light intensities and a difference frequency diffracted light proportional to the squared amplitude of the ultrasonic signal appear in a portion spatially overlapping with the pulsed ultrasonic signal 12 in the optical axis direction. This diffracted light passes through an aperture prepared in advance in the optical spatial filter 8 and is emitted to the outside of the signal processor.
Since the ultrasonic signal 11 and the pulsed ultrasonic signal 12 are traveling through the cell at velocities v ₁ and v ₂ respectively, the spatial width of the pulsed ultrasonic signal 12 within the cell is equal to the width of the light passing window 5 in the ultrasonic propagation direction. , and if it is sufficiently small compared to the minimum spatial period of the electrical signal to be processed, then
As if the ultrasonic signal 11 were the pulsed ultrasonic signal 12
is scanned at a speed (v ₁ to v ₂ ). Since the amplitude of the ultrasound pulse is constant depending on the magnitude and sign of the relative velocity of these two ultrasound signals, the signal obtained by the scanning is an expanded and compressed electrical signal to be processed in time. becomes. That is,
When the ultrasonic traveling speed v ₁ in cell 3 is smaller than the same speed v ₂ in cell 3', the change in the output light amount is
The waveform of the electric signal applied to the terminal 6 of 2 is shown with the time axis expanded. The time axis expansion rate Ke at this time is expressed as _Ke = _v1 / _v1 - _v2 ( _v1 > _v2 ) (3 ₎ using v1 and _v2 . Furthermore, when v ₂ is larger than v ₁ , the pulsed ultrasound signal 12 scans past the ultrasound signal 11, causing a reversal of the time axis. v ₁ ＜
When v ₂ < 2v ₁ , it is expansion inversion, and when 2v ₁ < v ₂ , it is compression inversion. In the case of v ₂ = 2v ₁ , the waveform is simply reversed. Next, consider a case in which two vibrators 1 and 1' are arranged opposite to each other, unlike the configuration shown in FIG. In this case, only the time axis compression operation is performed, and the compression ratio K _c
is expressed by the following equation using v ₁ and v ₂ .

K _c = 1 + v ₂ / v ₁ ...(4) The above is an explanation of the processing operation regarding the time axis, but furthermore, between the front surface of the light passing window 5 and the lens 7, there is an aperture approximately the same as the spatial width of the pulsed ultrasound. If you install an optical fixed pattern filter with
It becomes a time delay device with gate function. That is, the pulsed ultrasound for scanning, which was used for time axis compression in the previous example, is used for gate control, and only when the pulsed ultrasound exists overlapping the opening of the optical fixed pattern filter, the diffracted light is The configuration provides the following. In this case, the width and period of the pulsed ultrasound are arbitrary, and the delay time of the electrical signal to be processed is determined by varying the distance from the ultrasound transducer 1 to the opening of the fixed pattern with the ultrasound velocity v ₁ in the cell 3. The divided value is the value. Further, in order to perform time delay and time axis compression at the same time, it is possible to widen the aperture width of the fixed pattern and narrow the pulsed ultrasonic wave for scanning. In this case, time base compression and time delay are performed in the same manner as in the previous example, and the gate function is eliminated. In order to correct output errors due to ultrasonic attenuation within the cell, more accurate signal processing can be expected if the light intensity distribution of the light beam incident on the cell is changed using an optical filter. An area type optical filter may be used for the optical filter provided in this window portion. In this case, a light beam whose cross section is rectangular is used due to the combination of cylindrical lenses, and as a result, the effective usage rate of the light beam is increased. Furthermore, instead of making the cell an integrated structure using a transparent partition plate as shown in Fig. 3, it was made separately as shown in Fig. 4, and these optical axes and ultrasonic propagation directions were A method of matching and using them may also be considered. In this case, there is an advantage that cells suitable for the characteristics (frequency, period, etc.) of the electrical signal to be processed can be appropriately selected and used.

The present invention has the above-described configuration, and by using the simple acousto-optic electric signal processor of the present invention, it is possible to compress the time axis of electric signals, time delay having a gate function, and further achieve these two types. This has the effect of allowing signal processing to be performed in analog fashion in real time by combining the following.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an optical ultrasound signal processing cell used in the present invention, FIG. 2 is a diagram showing an optical processing system of the present invention, FIG. 3 is a diagram showing one embodiment of the present invention, and FIG. FIG. 3 is a diagram showing an example of a configuration using a single cell. In the figure, 1 and 1' are ultrasonic transducers, 2 and 2' are ultrasonic absorption members, 3 and 3' are cells, 4 and 4' are liquid substances, 5 and 5' are light transmission windows, and 6 and 6 ' is an electric signal input terminal, 7 is a lens, 8 is an optical spatial filter, 9
10 is a band-shaped plane wave light, 10 is a transparent partition plate, 11 is an ultrasound signal, 12 is a pulsed ultrasound signal, A is a sum frequency diffraction bright spot, and B is a difference frequency diffraction bright spot.

Claims (1)

[Scope of Claims] 1. One or more ultrasonic transducers 1, 1' that are provided on the inner surface of a cell that keeps a liquid substance therein and vibrate upon receiving an external electric signal, and the ultrasonic transducer one or more ultrasonic absorbing members 2, 2' provided on the opposite side of the cell for absorbing ultrasonic waves propagating in the liquid substance, and transmitting parallel laser beams from the outside. The plurality of ultrasonic propagation paths by the plurality of ultrasonic transducers are divided into a predetermined number by light transmission windows 5, 5' provided in the cell and opened in the direction of the propagation path of the ultrasonic waves. an ultrasonic signal processing cell having (predetermined number - 1) transparent partition plates 10; a lens 7 that receives the output light of the ultrasonic signal processing cell; an optical device provided at the focal point of the lens; an acousto-optic electrical signal processor comprising: a spatial filter 8; the laser beam enters through a light transmission window provided in the ultrasonic signal processing cell and then passes through all of the plurality of ultrasonic propagation paths; An acousto-optic electrical signal processor, characterized in that the ultrasonic transducers in the plurality of cells are respectively arranged so as to pass perpendicularly to the cell. 2. The acousto-optic system according to claim 1, characterized in that liquid substances having different ultrasonic propagation times are kept in a predetermined number of sections divided by the transparent partition plate 10 of the ultrasonic signal processing cell. Electrical signal processor. 3. One or more ultrasonic transducers 1, 1' that are provided on the inner surface of a cell that keeps a liquid substance therein and that vibrate upon receiving an external electrical signal, and the cell provided with the ultrasonic transducers. one or more ultrasonic absorbing members 2, 2' provided on opposite sides of the cell for absorbing ultrasonic waves propagating in the liquid substance; a plurality of ultrasonic signal processing cells each having light transmission windows 5, 5' having a shape open in the longitudinal direction of the ultrasonic wave propagation path; a lens 7 for receiving output light from the ultrasonic signal processing cells; and the lens. an acousto-optic electrical signal processor, comprising: an optical spatial filter 8 provided at a focal position of the plurality of cells; An acousto-optic electrical signal processor characterized in that each of the vibrators in the cell is arranged so that the laser beam passes perpendicularly to all of the plurality of ultrasonic propagation paths. 4. Claim 4, wherein one or a desired cell of the plurality of ultrasonic signal processing cells maintains therein a liquid substance having an ultrasonic propagation time different from that in the other cells. 4. The acousto-optic electrical signal processor according to item 3.