JPS6227695B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an acousto-optic electrical signal processing method used in an acousto-optic light modulator (ULM) that processes pulse signals by utilizing light diffraction phenomenon caused by ultrasonic waves. The present invention relates to a liquid cell for use.

Traditionally, there have been spatial signal processing devices using optical lens systems and acousto-optic modulators, which have been used to compress radar signals, real-time spectrum analyzers, etc.
It was widely used. However, because these use surface acoustic wave devices that use a solid ultrasonic propagation medium, and because they only utilize diffraction phenomena, the signal frequency range that can be effectively used is from several tens of MHz to several GHz. This is a high band.

The invention of the present application was made to target signals of a lower frequency (several MHz) than the conventional one, and is characterized by the use of a liquid substance as an ultrasonic propagation medium.

The liquid cell of the present invention is used as a pulse compressor in various measurement devices using ultrasonic waves, and it converts one electrical signal (ultrasonic frequency) into an ultrasonic wave and radiates it into media with different propagation velocities. , it is possible to generate two or more ultrasonic signals with spatially different wavelengths (periods). Since these plurality of ultrasonic signals need to maintain accurate spatial phase relationships, it is desirable that they be generated by a single ultrasonic transducer. Therefore, in the present invention, one cell is divided into two or more chambers with a partition plate that transmits light, and each chamber is filled with a liquid medium having different ultrasonic propagation speeds so as not to mix with each other. Ultrasonic waves are emitted into these media from one wall of the structure, and the other wall is equipped with an ultrasonic absorbing member.

Examples of the present invention will be described below.

FIG. 1a is a diagram showing the structure of an embodiment of a liquid cell for acousto-optic electrical signal processing according to the present invention.
An ultrasonic transducer 3 and an ultrasonic absorbing member 4 are provided to face each other on one set of opposing wall surfaces of the rectangular parallelepiped cell 1, and one set is provided on the other opposing wall surface of the rectangular parallelepiped.
A pair of light transmission windows 2a and 2b are provided. Through this window, monochromatic plane wave light enters the cell from outside the cell, passes through the cell, and exits outside the cell. Furthermore, the inside of the cell is divided into two parts with one transparent partition plate 5.
It is separated into two chambers, and liquid is not allowed to pass through the area where the partition plate and the vibrator come into contact, that is, the edge of the partition plate, in order not to interfere with the vibration of the vibrator.
Furthermore, the two chambers are separated using an elastic member 6 having elasticity. These two chambers are filled with liquid substances 7a and 7b having different degrees of ultrasonic transmission, but the elastic member and the partition plate keep the liquids liquid-tight so that the liquids do not leak into each other. The ultrasonic transducer also has an input terminal 8 for supplying an electrical signal.
is connected.

FIG. 1c shows another embodiment of the invention. That is, two partition plates are provided in a single cell to divide the cell into three chambers, and each chamber is filled with a different liquid substance 7a, 7.
b, 7c are filled. It is clear that the outer shape of the cell is not limited to a rectangular parallelepiped.

FIG. 2 shows how monochromatic plane wave light 9 is introduced from the outside into the liquid cell according to the present invention, passes through the liquid of the cell, and is then converged by a lens 10 placed outside the cell. There are multiple types of liquids (two types in FIG. 2) with different propagation velocities in the cell, and the ultrasonic waves excited by the electrical input signal of the frequency form a sinusoidal phase grating. Let the propagation velocity be v ₁ , v ₂
If (v ₂ > v ₁ ), then in each medium d ₁ = v ₁ /, d ₂ =
A grating with a grating spacing d ₁ (i=1,2) of v ₂ / is formed, and this grating traverses the monochromatic plane wave light at velocities v ₁ and v ₂ , respectively. Therefore, the transmitted monochromatic plane wave light forms a diffraction image by the Fourier transform optical system, which is the lens 10. This is derived from Fraunhofer's diffraction principle, and a diffraction bright spot is generated in the optical filter 11 disposed on the focal plane of the lens 10. Outside the central bright spot, d ₁ , d ₂ , 1/(1/
d ₁ ±1/d ₂ ), eight bright spots are generated. Among these, 1/(1/d ₁ ±1/
When a bright spot with a lattice constant of _d2 ) is received by the photoelectric converter 12 through the pinhole of the optical filter 11,
An electrical signal (cross-correlation function) indicating the degree of overlap of two ultrasound waves within the cell is obtained.

By using a signal obtained by dividing the ultrasonic sine wave electrical signal into a specific period and frequency, and by using the electrical signal (cross-correlation function) obtained therefrom, a pulse signal compression device with higher accuracy and higher resolution can be obtained. be able to.

As described above, by using the liquid cell for acousto-optic electrical signal processing of the present invention, a pulse compressor for relatively low frequency signals (several KHz to several MHz) can be easily realized. For this reason, when applied to sonar, etc., the S/N ratio improves, and the ultrasonic generation and detection transducer of sonar etc. can be made smaller (for example, a few mm square) to the extent that the S/N ratio is improved. or
It has become possible to reduce the ultrasonic power consumption.

The present invention has great practical effects, such as being able to be used in small ultrasonic detection devices used for biological measurement (mainly Toppur blood flowmeters, etc.).

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the present invention, and FIG. 2 is a diagram showing a state in which the liquid cell for acousto-optic electrical signal processing of the present invention is used. 1 is a cell, 2a and 2b are light transmission windows, 3 is an ultrasonic transducer, 4 is an ultrasonic absorption member, 5 is a partition plate, 6 is an elastic member, 7a, 7b, and 7c are liquid substances, and 9 is a monochromatic plane wave light , 10 is a lens, 11 is an optical filter, and 12 is a photodetector consisting of a photoelectric converter.

Claims (1)

[Claims] 1 In a liquid cell for acousto-optic electrical signal processing: one ultrasonic transducer 3 provided inside the cell and excited by an electric signal; an ultrasonic absorbing member 4 provided on both opposing walls of the cell to transmit monochromatic plane light outside the cell at right angles to the ultrasonic propagation path from the vibrator to the absorbing member; light-transmitting windows 2a, 2b; a light-transmitting partition plate 5 that divides the inside of the cell into at least two chambers parallel to the propagation path and the light-transmitting window; an elastic member 6 interposed between the vibrator and an edge of the partition plate adjacent to the vibrator to hold the vibrator and separate the chambers in a liquid-tight manner; Filled with the above 1
Multiple types of liquid substances 7 that propagate ultrasonic waves emitted by different ultrasonic transducers at different speeds.
A liquid cell for acousto-optic electrical signal processing, comprising: a, 7b.