JPS6310387B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to an acoustic image recorder.

A more recent development in the field of microscopy is the use of acoustic radiation to "see" objects. That is, an acoustic wave is focused into the water chamber by an appropriately shaped acoustic lens, the specimen is mechanically scanned through the focal point, and the acoustic radiation modulated by passing through the specimen is transmitted to another received by an acoustic lens. Such a device was introduced in 1973 by the Institute of Electrical and Electronic Engineers' Ultrasonics.
It is described in a paper entitled "Scanning Archaeological Microscope" presented by R.A. Lemons and C.F. Quartz at the Symposium Proceedings (Cat. No. 73 CHO 807-8SU).

Such devices can be used to provide information about a specimen at numerous points spaced above or below the surface of the specimen. In determining this information, one only needs to consider changes that have occurred in the specimen since previous records are available. The change may occur in amplitude or phase or both. Conventional equipment uses only phase contrast or only amplitude contrast;
It is unlikely that it has previously been possible to record simultaneous changes in both variables over time, although known or unknown combinations of both could be used to provide images.

The purpose of the present invention is to measure the physical quantity of an object as a function of amplitude and phase, detect simultaneous changes in two variables, amplitude and phase, of the physical quantity of the object after time, and detect changes in the object. The object of the present invention is to provide a detection device.

According to the invention, said object comprises means for irradiating an object with a focused acoustic radiation beam excited by a first alternating electrical signal and a means for irradiating an object with a focused acoustic radiation beam in the vicinity of the focal point; means for receiving a modulated acoustic radiation beam and deriving a second alternating electrical signal from the received modulated beam; a first reference electrical signal derived at a known phase from the first alternating electrical signal; means for generating a second reference electrical signal derived from the first alternating electrical signal and having a phase shifted between 80° and 100° with respect to the first electrical reference signal; Signal and 1st
a reference electrical signal of 80 to derive a first mixed output signal from these signals, and a second alternating electrical signal and a second reference electrical signal to derive a first mixed output signal of 80 a mixing means for deriving a second mixed output signal having a phase difference in the range from 100° to 100°; a first mixed output signal sent from the mixing means and a second mixed output signal;
means for generating a signal indicating the physical quantity of the object from a mixed output signal of means for irradiating the object with a focused acoustic radiation beam excited by the first alternating electrical signal, and a focal plane of the object and the acoustic beam; a scanning means arranged to cause a movement relative to the focal point of the object, and receiving a beam of acoustic radiation modulated in phase and amplitude by the object in the vicinity of the focal point; means for deriving two alternating electrical signals; a first reference electrical signal derived from the first alternating electrical signal with a known phase; means for mixing the second alternating electrical signal and the first reference electrical signal and generating a second reference electrical signal from these signals; A second mixed output signal is derived from the first mixed output signal, and a second alternating electrical signal and a second reference electrical signal are mixed to produce a second mixed output signal having a phase difference between 80° and 100° from the first mixed output signal. a mixing means for deriving a signal; a means for generating a signal indicating a physical quantity of an object from a first mixed output signal and a second mixed output signal sent from the mixing means; and a plurality of relative positions of the object. means for storing a signal indicative of a physical quantity of the object corresponding to each, and combining said signal stored for each position of the object with a signal indicative of the physical quantity of the object that is subsequently supplied for each position of the object; combining means for detecting changes in an object, wherein both the first electrical reference signal and the second electrical reference signal have the same frequency as the first alternating electrical signal.

Further in accordance with the invention, there is provided a method for detecting a change in an object, the method comprising: illuminating the object with a focused acoustic radiation beam excited by a first alternating electrical signal; receiving an acoustic radiation beam modulated in phase and amplitude by the object in the vicinity of and deriving therefrom a second alternating electrical signal, and a reference signal derived at a known phase from the first alternating electrical signal; providing a first in-phase signal, coherently mixing a second alternating electrical signal and a reference signal to derive a first in-phase signal, and a second alternating electrical signal to provide a first quadrature signal; in the range from 100° to 100°, conveniently mixed with a 90° phase shifted reference signal, storing the first in-phase signal and the first quadrature signal, and after a time interval, receiving an acoustic radiation beam modulated by the same portion;
deriving therefrom a third alternating electrical signal and similarly deriving a second in-phase signal and a second quadrature signal; and the first signal stored for detecting changes in the object. and a second signal.

The acoustic radiation beam is transmitted through or reflected by the object.

The stored first signal and the second signal may be separated by simple addition or subtraction, or by multiplying one signal by a certain factor and then adding or subtracting, or by other mathematical operations. Can be combined.

Typically, the method further includes causing a relative movement of the focal plane of the object and the focal point of the acoustic beam to derive a first in-phase signal and a first quadrature signal at each of the plurality of relative positions. , each first in-phase signal and the first
and after said time interval,
repeating the movement, deriving a second in-phase signal and a second quadrature signal at each position, and combining the stored first signal and the second signal for each position. consists of doing.

A specific example will be explained below with reference to the drawings.

In FIG. 1, a scanning transmission acoustic microscope 11
consists of first and second sapphire crystals 10, 12, each crystal 10, 12 having a polished spherical concave surface 14, 16, and a piezoelectric transducer 18, on the opposite side of the concave surface. 20 are in contact. Both concave surfaces are placed adjacent to each other, with each concavity approximately 0.13
It has a radius of curvature of mm, and a water droplet 22 is held between both concave surfaces by surface tension.

When an alternating voltage is applied to the transducer 18, a plane wave of acoustic radiation is created that travels through the crystal 10 and into the water droplet 22. Curved surface 14 focuses this beam into the water. When a thin sample 24 mounted on a polyethylene terephthalate film 26 is placed at a focal point, the specimen modulates the acoustic radiation passing through it, in this case concave surfaces 14, 16 are arranged so that the respective focal points are at the same location. When positioned, the crystal 12 receives radiation from the focal point and the associated
An AC signal is provided to converter 20. When the specimen is scanned through the focal point, for example in a raster pattern, a point-by-point image is created from the signals at transducer 20. This is the basic scanning acoustic microscope described by Lemons and Quartz and referenced above.

Additional equipment is required to record changes in the object. Converter 18 is fed from a 1 GHz oscillator 28 via amplifier 30 and switch 32, with the other converter 20 connected to switch 34. Switches 32, 34 are controlled by a pulse generator 36; one switch 34 is
Delay line 38 is operated to allow transit time of the acoustic radiation through the microscope. These switches 32, 34 are time gated and allow only the necessary signals, i.e. those corresponding to the direct passage of the acoustic radiation through the microscope, to pass through the switch 34, while the acoustic radiation reflected from the curved surfaces 14, 16 It is used to block signals corresponding to radiation.

The switch 34 includes an amplifier 40 and a bandpass filter 42.
and to a first input of the mixer 44. A second input of this mixer 44 is connected to the oscillator 28 via a delay line 46 and a switchable phase shifter 48 . The output of the mixer is passed through a low pass filter 50
It is connected to the.

In use, the delay line 46 provides a delay approximately equal to the transit time of the acoustic radiation through the microscope, greatly reducing the effects of short-term oscillator instability. Since the low pass filter 50 suppresses undesirable modulation products, its time constant is chosen to effectively integrate the detected pulse signal.

In the following description, the combination of the delay line 46 and the switchable phase shifter 48 will be used to provide the input of the mixer 44 with the output signal that the microscope would give in the absence of an object, i.e. the first directly transmitted signal. The apparatus is arranged to provide a signal that is in phase or in quadrature with the phase of the alternating electrical signal.

Mixer 44 thus combines two signals that are either exactly in phase, in-phase signals, or quadrature signals that differ in phase by 90°.
This makes it possible to clarify the description of the invention using simple mathematics.

However, this condition is not essential. As long as the phase of the signal applied via the phase shifter and the phase of the second alternating electrical signal are always the same or differ by 90°, then they are usually "in phase" and "in quadrature". Certain two signals can be derived. Phase changes in the object can then be determined. The actual phase of the two signals switched out of the phase shifter must be known, and the phase of one signal can be chosen arbitrarily to provide an "in-phase" signal.

Furthermore, the phase shifter is precisely
There is no need to change the phase by 90°. The phase shift can be effected by one specific value within the range of 80° to 100°. The actual phase shift must be accurately determined by correction, and simple first-order numerical corrections must be made to the output data. Even if the phase difference between the signal that is not phase-shifted in the phase shifter and the signal that is phase-shifted in the phase shifter is even lower than 80°, as long as its magnitude is precisely known, Although it would probably allow detection of phase changes in the object, it would be necessary to make larger corrections to the data.

Referring to FIG. 2, it is assumed that the output of oscillator 28 (first alternating electrical signal) is A cosωt. With no sample 24 and phase shifter 48 set to zero phase (φ=0°), delay line 46 is selected or set as follows. That is, the input from phase shifter 48 into mixer 44 (reference signal) and the input from microscope 11 through switch 34 into mixer 44 (second alternating electrical signal) are in phase, and therefore: Since the actual signal delays are equal, both are chosen to be considered A cosωt. If phase shifter 48 performs a 90 degree phase shift, the input from this phase shifter to mixer 44 is considered to be A sinωt. The transfer function of sample 24 is B(x), <θ゜, that is, the amplitude component B(x)
and the associated phase θ°, the output signal of the microscope 11 is B(x) cos {ωt + θ(x)}, and if certain constant factors are ignored, this signal is the output signal of the mixer 44. supplied to the first input.

The output of the mixer 44 is the product of the two input signals: In this case, when φ=0, the output = A cos ωt B(x) cos {ωt + θ(x)} = AB(x)/2[cos θ( x) + cos {2ωt + θ(x)
}] The signal that the low-pass filter 50 allows to pass is AB(x)/2cosθ(x)...(1) Also, when φ=90°, output=A sinωt・B(x)cos{ωt+θ( x)} =AB(x)/2[-sinθ(x)+sin{2ωt+θ(x
)}] The signal that the low-pass filter 50 allows to pass is AB(x)/2sinθ(x)...(2) When the two quantities expressed by equations (1) and (2) are measured, B( x) and θ(x) can be determined separately.

That is, the signal passed through the low-pass filter 50
AB(x)/2cosθ(x) and signal AB(x)/2sinθ(x
) is an arithmetic processing section in the sample and hold circuit 52, and formula (1)
B(x) and θ(x) can be obtained by solving for B(x) and θ(x) by combining and formula (2).

Suppose that the position of one point in the object is represented by (iδx, jδy). Here, δx and δy are the dimensions of the image elements, and i and j are integers.
Let Bij be the signal obtained in the arithmetic processing unit from the image elements at the positions iδx, jδy of the object, and Cij be the signal obtained in the arithmetic processing unit from the image elements at the positions iδx, jδy of the object after changing the object. . Bij is determined by the amplitude of the incident ultrasound signal and the transfer function of the specimen in the image element, and
Cij is determined by the amplitude of the incident ultrasound signal after the object change and the transfer function of the specimen in the image element. Bij=f[B(Xij), θ(Xij)] and Cij=
Once records have been created for g[C(Xij), θ(Xij)], they can be combined in several ways. For example, (Bij−Cij) contains all the information about the change and is displayed properly. If (Bij + KCij) is displayed selectively (where K is a complex constant), then Bij gives the reference size of the original image, and adding KCij creates interference fringes similar to those familiar in optics. will occur. These fringes can be considered to be contour lines that appear in response to changes. Other mathematical operations are also possible. For example, K=Cij (Cij is the complex conjugate of Cij)
In addition, it is also possible to display (Bij + Cij・Cij). The expression (Bij+Cij・Cij) is applied when amplitude changes mainly occur in the object.

Referring again to FIG. 1, when phase shifter 48 has a phase shift of 0 degrees and when it has a phase shift of 90 degrees, object 26 is scanned stepwise in a raster pattern, and the output of mixer 44 is recorded for each point above. The object is then modified, or allowed to be modified in some way, and again manipulated exactly in the same raster pattern, and a recording is made at each point φ=0 and φ=90°. As a result, the two records consist of Bij and Cij and are combined in any manner by suitable digital processing operated in a conventional manner. An advantage of the present invention is that the most appropriate display format can be easily selected.

A device for controlling the recording of Bij and Cij will be described below with reference to FIG.

The low pass filter 50 is connected through a sample and hold circuit 52 and an A/D converter 54, through a control line system 56, to a control and recording circuit 58, and further connected to a step motor drive and control circuit 60. ing. circuit 60
are two step motors 62, 64 that control the position of the film 26 to which the object 24 is attached.
control. Circuit 58 is also connected to a display unit 66, such as a cathode ray tube.

The control circuit 58 also includes the sample and hold circuit 5
2. Controls the A/D converter 54 and the switchable phase shifter 48.

A typical cycle under control of control circuit 58 for recording signals Bij and Cij is as follows.

(i) Phase shifter 48 is set to φ=0.

(ii) The step motors 62, 64 are instructed to move the object to a predetermined position, ie, a point (iδx, jδy), and to be stopped at that position.

(iii) After a short delay to allow the system to stabilize, the sample and hold circuit 52 is set to hold the analog signal level at its input. This corresponds to the output signal from the microscope 11 focused on the point (iδx, jδy),
AB(Xij)/2cosθ(Xij).

(iv) A signal AB(Xij)/2cosθ(Xij) appears at the input of the arithmetic processing section in the sample-and-hold circuit 52.

(v) Thereafter, the sample-and-hold circuit 52 is in a state where input can flow again.

(vi) Phase shifter 48 is set to φ=90°. The above steps (iii), (iv) and (v) are repeated and the signal
AB(Xij)/2sinθ(Xij) appears at the input of the arithmetic processing section.

(vii) In the arithmetic processing section, B (Xij) and θ (Xij) are determined from the signal AB (Xij) / 2cos θ (Xij) and the signal AB (Xij) / 2 sin θ (Xij), and the A/D converter 54 passes the digital signal corresponding to Bij=f[B(Xij), θ(Xij)] to the storage section of the control circuit 58, and the digital signal corresponding to Bij is stored in the storage circuit.

(viii) The step motor moves the object to a new position and the measurement cycle is repeated.

After the object is scanned in a raster pattern, the object is modified or allowed to change.
The cycle is then repeated scanning the object in exactly the same pattern. 1st and 2nd record Bij
Cij is combined with the memory circuit in the required manner,
Is displayed.

It will be appreciated that many variations may be made to the device. For example, if a sufficiently stable oscillator is used, the delay line 46 need not provide a delay time equal to the transit time of the acoustic wave from the microscope, but only a small shift so that the reference signal is in the desired phase. Just give the phase. Delay line 46 and phase shifter 4
It will be appreciated that there are important differences in the function with 8, despite the fact that both involve a change in phase. provided by phase shifter 48
The purpose of the 90° phase shift is to provide a quadrature reference signal. The absolute value of the phase of the signal in the signal path through the microscope is arbitrary; the essential point is that the phase shift difference between the two possible reference signals is 90°.
The use of delay line 46 also allows greater tolerance for oscillator stability.

Other variations are also possible. For example, if the microscope is positioned so that there is no reflection of acoustic radiation, the received signal does not need to be pulse-gated. Also, the phase and amplitude signals for each position may be derived simultaneously rather than sequentially, and the scanning operation need not be stepwise, but may be continuous. Furthermore, the acoustic microscope does not need to be a sapphire crystal with a concave surface, and the British patent application No. 20713/77 was filed on the same day (Japanese filing date: May 16, 1978).
It can also take the form described in the issue.

Furthermore, a reflection mode can also be used instead of the transmission mode as described above in microscopy operation.

In the above embodiment of the apparatus of the present invention, the means for irradiating the object include a sapphire crystal 10, a spherical concave surface 14, a piezoelectric transducer 18, a water droplet 22, an oscillator 2
8, an amplifier 30, a switch 32 and a pulse generator 36, the scanning means consisting of a control circuit 58, a control circuit 60, step motors 62, 64 and a control line system 56, means for deriving a second alternating electrical signal; are a sapphire crystal 12, a spherical concave surface 16, a piezoelectric transducer 20, a water drop 22, a switch 34, a pulse generator 36, a delay line 38, and an amplifier 4.
0 and a bandpass filter 42, the means for generating the reference electrical signal consists of an oscillator 28, a delay line 46, a phase shifter 48, a control circuit 58 and a control line system 56, the mixing means consists of a mixer 44,
The means for generating a signal indicating the physical quantity of the object includes a low-pass filter 50, a sample-and-hold circuit 52,
A/D converter 54, control line system 56
and a control circuit 58, and means for storing signals indicating physical quantities of the object is a control line system 5.
6 and a memory circuit 58, and the coupling means consists of the memory circuit 58.

The device of the present invention detects changes in the object by detecting changes in only the phase or changes in only the amplitude, or by measuring phase changes and amplitude changes separately and combining them. Compared to conventional devices that measure the phase and amplitude simultaneously, changes in the object are detected by measuring changes in both phase and amplitude, so changes in the object can be detected extremely accurately. It has the advantage of being able to measure

Examples of changes in objects observed by the apparatus and method of the present invention include measurements of dimensional changes, measurements of changes in physical properties such as viscosity and elasticity, and changes in biological properties such as cell growth and division. These include changes resulting from chemical processes, as well as observation of crystal growth.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the device of the invention, and FIG. 2 is a simplified block diagram of portions of said device showing electrical signals and their coupling. 10,12...Saphia crystal, 14,16
... Concave surface, 28 ... Oscillator, 32, 34 ... Switch, 38, 46 ... Delay line, 48 ... Phase shifter.

Claims (1)

Claims: 1. Means for irradiating an object with a focused acoustic radiation beam excited by a first alternating electrical signal and modulated in phase and amplitude by the object in the vicinity of the focal point. means for receiving a modulated acoustic radiation beam and deriving a second alternating electrical signal from the received modulated beam; a first reference electrical signal derived at a known phase from the first alternating electrical signal; means for generating a second reference electrical signal derived from the alternating electrical signal and having a phase shifted between 80° and 100° with respect to the first reference electrical signal; a first reference electrical signal to derive a first mixed output signal from these signals; and a second alternating electrical signal and a second reference electrical signal to derive a first mixed output signal. a mixing means for deriving a second mixed output signal having a phase difference in the range of 80° to 100°; and a first mixed output signal sent from the mixing means.
means for generating a signal indicative of a physical quantity of an object from a mixed output signal and a second mixed output signal, wherein both the first reference electric signal and the second reference electric signal are connected to a first alternating signal. A device that detects changes in an object that have the same frequency as an electrical signal. 2. The apparatus of claim 1, wherein the first reference electrical signal has a predetermined phase relationship with respect to the first alternating electrical signal. 3. The apparatus of claim 1, wherein the first reference electrical signal is in phase with the first alternating electrical signal. 4. Apparatus according to any one of claims 1 to 3, wherein the second electrical reference signal has a phase that differs by 90° from the phase of the first electrical reference signal. 5 means for irradiating an object with a focused acoustic radiation beam excited by a first alternating electrical signal and for causing relative movement in the focal plane of the object and the focal point of the acoustic beam; scanning means disposed; means for receiving a beam of acoustic radiation modulated in phase and amplitude by the object in the vicinity of the focal point; and means for deriving a second alternating electrical signal from the received modulated beam; a first reference electrical signal derived from an alternating electrical signal with a known phase; means for generating a second alternating electrical reference signal; and means for mixing the second alternating electrical signal and the first reference electrical signal to derive a first mixed output signal from the signals; Mixing means for mixing the electric signal and a second reference electric signal to derive a second mixed output signal having a phase different from the first mixed output signal in a range of 80° to 100°, and sending from the mixing means. means for generating a signal indicating a physical quantity of the object from the first mixed output signal and the second mixed output signal, and storing a signal indicating the physical quantity of the object corresponding to each of the plurality of relative positions of the object. and a coupling means for coupling the signal stored for each position of the object with a signal indicative of the physical quantity of the object that is subsequently supplied for each position of the object; An apparatus for detecting changes in an object, wherein both the signal and the second reference electrical signal have the same frequency as the first alternating electrical signal. 6. The apparatus of claim 5, wherein the first reference electrical signal has a predetermined phase relationship with respect to the first alternating electrical signal. 7. The apparatus of claim 5, wherein the first reference electrical signal is in phase with the first alternating electrical signal. 8. Apparatus according to any one of claims 5 to 7, wherein the second electrical reference signal has a phase that differs by 90° from the phase of the first electrical reference signal. 9. Claims in which the scanning means moves the object stepwise in a repeatable pattern in the focal plane, and at each step of this movement a first mixed output signal and a second mixed output signal are derived. The apparatus according to any one of clauses 5 to 8.