RU2011194C1 - Acoustic microscope - Google Patents

Abstract

FIELD: testing materials. SUBSTANCE: device has an ultrasonic transducer, a processing unit for processing the signals from the ultrasonic transducer during scanning the surface of material being tested. The signal processing unit is made in the form of coupled amplitude discriminators, storage units, counter and analogue- to-digital converter. EFFECT: enhanced accuracy due to programming parameters of the signal processing unit. 8 dwg

Description

 The invention relates to measuring technique and can be used for non-destructive quality control of materials.

 It is known that an ultrasonic (ultrasound) television device for controlling the quality of materials containing an ultrasonic transceiver transducer (SPP) installed with the possibility of moving along the surface of the controlled material using a stepper motor in two coordinates, a pulse shaper that is fed to the SPP, the SPP irradiates the controlled material, receives the signal reflected from it and feeds it to the television unit, on which the "image" of the internal structure of the material being monitored is formed. A line-frame scan on a television unit is formed using line-frame generators synchronized with blocks that generate horizontal and vertical signals [1].

 However, this device has a low resolution in the scanning plane, high requirements for the perpendicularity of the axis of the sensor and low speed. The device does not allow working with objects of complex shape and to obtain a three-dimensional image of the structure of the object.

 It is also known a device for ultrasonic quality control of materials, containing ultrasound SPP, with which acoustic pulses are generated into the controlled object, generated by a pulse generator, the duration and frequency of which is set by the master unit; the shape and amplitude response of the reflected pulses are displayed on an oscilloscope. Measurement of the delay time of the reflected signal is also carried out. By the amplitude and time characteristics of the signals, by comparison with the reference characteristics recorded in the memory unit, the structure of the material is estimated — granularity, phase composition, defects, and also the depth [2].

 This device also has a low speed and does not allow working with objects of complex shape.

 The purpose of the invention is to increase the resolution in the scanning plane and increase the selectivity in depth, as well as providing work with objects that have a non-planar shape.

 This goal is achieved in that an acoustic microscope containing a pulse generator, consisting of a series-connected quartz oscillator and a frequency divider, an acoustic transceiver installed to move relative to the surface of the test object, an information storage unit connected to the control and processing unit, to the output of which an information display unit is connected, as well as an information input and output unit, an analog-to-digital converter and a digital-to-analogue A transducer connected by communication buses to a control and processing unit is characterized in that a counter and a signal conditioning amplifier are connected in series between the output of the frequency divider and the acoustic transceiver, as well as a memory block and a serially connected limiter amplifier, the input of which is connected to the line the connection of the amplifier-driver and the acoustic transceiver, an amplifier with an adjustable gain, an analog switch, a detector with a ramp shift component, a video amplifier with adjustable gain and a storage and sampling unit, the output of which is connected to the input of an analog-to-digital converter, while the output of the crystal oscillator is connected to the second input of the counter, the second, third and fourth outputs of which are connected respectively to the second input of the block storage and sampling, the second input of the analog-to-digital converter and the second key input, the output of the memory unit is connected to the control input of the frequency divider, and its inputs are respectively control outputs and the fifth output of the counter, the control inputs of the amplifier with adjustable gain, and the video amplifier with adjustable gain are connected to the corresponding inputs of the control and processing unit, and the control input of the detector with programmable DC offset is connected to the output of the digital-analog converter, generator pulses made in the form of series-connected quartz oscillator and frequency divider.

 In FIG. 1 shows a structural electrical diagram of the proposed acoustic microscope; in FIG. 2 are diagrams explaining the operation of the microscope.

 The acoustic microscope contains a series-connected quartz oscillator (KG) 1, a frequency divider 2, the control input of which is connected to the output of the memory unit 3, a counter 4, an amplifier-shaper 5 and a sensing element 6, which is an acoustic transceiver, and also connected in series limiter amplifier 7, the input of which is connected to the output of element 6, an amplifier 8 with an adjustable gain, an analog switch 9, a detector 10 with a programmable shift of the DC component, video a variable amplifier 11, a storage and sampling unit (BHV) 12, an analog-to-digital converter (ADC) 13 and a control and processing unit (BUO) 14, as well as a digital-to-analog converter (DAC) 15 connected between the output of the BUO 14 and the first the control input of the detector 10, a stepper motor 16, the control input of which is connected to the second control output of the control unit 14, as well as the information display unit (BOI) 17, the information storage unit (BCH) 18 and the information input and output unit (BVVI) 19 connected to BUO 14, while the output of KG 1 is connected to By the counter 4, the second, third and fourth outputs of the counter 4 are connected respectively to the second inputs of BHV 13, ADC 14 and analog key 9, BU 14 is also connected to the control inputs of video amplifier 11, memory unit 3 and amplifier 8.

 Acoustic microscope works as follows.

 First, the device is pre-configured. To do this, in the working area of the sensing element 6, which is an acoustic lens with an acoustic transducer or a spherical lens placed on it, the test sample is placed. The shape of the acoustic signal reflected from the sample is taken over a wide time interval. The operator analyzes the waveform and, depending on the nature of the sample, manually selects a specific image acquisition procedure from the keyboard and sets up the microscope's transceiver path.

 Next, KG 1 gives reference pulse signals with a frequency of 100 or 200 mg Hz (Fig. 2, a). In the frequency divider 2, by dividing the repetition rate of these pulses, pulses are formed with a given time interval (Fig. 2, c), which are pulses that synchronize the operation of the entire device.

 The division ratio of the frequency divider 2 is set by BP 3, the contents of which in each cycle of the device are updated using the BWO 14.

 In counter 4, pulses with different durations are formed, which are synchronizing for the operation of VHV 12 (Fig. 2, d), ADC 13 (Fig. 2, f) and key 9 (Fig. 2, f).

 From the output of the counter 4, the probing signal (Fig. 2, e) is fed to the amplifier-driver 5, where a pulse of a special shape is formed from it (Fig. 2, e), which is converted into an ultrasonic signal by means of the sensing element 6, and is radiated into the object under study, and taken after reflection from it (Fig. 2, d).

 The reflected pulse is pre-amplified and limited to a level not exceeding the threshold value in the amplifier-limiter 7 (Fig. 2, e). The limit threshold value is selected from the condition of protecting the amplifier-organizer 7 from breakdown by the output signal of the amplifier-former 5.

Further, in the amplifier 8 with a programmable gain K _y, it is amplified and fed to the analog switch 9. The value of K _{y is} programmed in the control unit 15 so that the maximum received signal does not overflow the ADC 13. The analog switch 9 samples the received pulse in the time interval, set by the strobe from the counter 4 (Fig. 2, e).

 In the detector 10, the input signal is detected with a shift of the DC component (Fig. 2, k) by the amount specified by the BWO 14 through the DAC 15. The shift of the DC component is necessary to improve the image if the useful signal is against the background of interference from foreign objects or noise.

 After detection, the signal is amplified by a video amplifier 11, the gain of which is set by the BWO 14.

 BHV 12 remembers the signal received on it for a time interval specified by strobe (2), which is determined by the time of the analog-to-digital converter in the ADC 13.

 The information converted from the analogue to digital using ADC 13 is then transferred to BUO 14, which controls the process of obtaining and displaying information: directly during one cycle, the parameters of the transceiver path are changed, adapting its operation to the parameters of the object depending on its properties; set all the time intervals, the amplification factors of the amplifiers 8 and 11, as well as the magnitude of the shift of the constant component of the detector 10.

 To study the entire surface of the object, the sensing element 6 is installed with the ability to move in three coordinates using a stepper motor 16, while the scanning step is set using signals from the BWO 14.

 The resulting image of the structure of the object during scanning is displayed on BOI 17. The information input and output unit 19 allows you to manually select the operating mode of the microscope and print the resulting image.

 At each scanning point, the delay time Δ t can be changed between two control pulses — a pulse that starts the output driver 5 and a pulse that controls the opening of the analog key. Thus, the shape of the acoustic signal reflected from the sample is taken and analyzed in the BUO 14.

 Depending on the type of sample, the value of the entrance gate, the delay time Δ t, and the gain of the limiting amplifier 7 are further adjusted to reduce the amount of interference caused by the presence of signals reflected from surface areas of the sample under study located in close proximity to the studied zone or caused by the presence of signals of unwanted modes of ultrasonic vibrations.

 If the defect is located near the rear surface of the sample, then the signals reflected from the defect and from the rear surface of the sample merge, and the analysis of their shape allows you to detect the defect.

If it is necessary to control the adhesion of layers during gluing, welding, soldering, galvanic deposition, etc., of a multilayer material with a fixed layer thickness, but not absolutely flat, analyzing the received signal, determine the distance to the surface of the sample and in accordance with this set the value of K _y with given the change in this distance.

 In FIG. 3 shows a diagram of the algorithm of the microscope in the mode of compensation of curvature of the surface of the sample; in FIG. 4 is a diagram of the algorithm of the microscope; in FIG. 5 is a diagram of the algorithm of the microscope in the shaper circuit - BUO 14; in FIG. 6 is a diagram of a microscope operation algorithm in a chain of blocks 1-4; in FIG. 7. and 8 are diagrams of the algorithms of operation of block 14.

 Thus, the proposed microscope allows you to get an unlimited large scanning field; makes it possible to decide on the presence or absence of a defect in a sample, for example, by splitting an acoustic pulse; measuring and recording only the amplitude of the split pulse, which allows you to get an image of the defects of the sample without first recording the entire array of data corresponding to the entire thickness of the sample. This saves computational resources (for recording an array of 512x512 pixels with a scan in depth along 512 channels, about 64 MB of RAM is required) and the time it takes to get an image.

 The proposed block diagram of the microscope is constructed in such a way that BUO 14 can program its entire path during one cycle of operation, i.e., between two successive radiation pulses of ultrasound. This achieves the adaptation of the microscope to the object at each measured point by reconfiguring the microscope in depth by changing the time intervals of the analog sample of the received signal and in amplitude by changing the gain of the microscope.

 The design of the transducer used in this microscope in the form of an acoustic lens placed in the shell into which the immersion liquid is supplied allows an unlimited scanning field to be obtained.

 The microscope allows you to work with non-planar objects, with objects of complex structure.

 The signal reflected from the lens, as a rule, has three components - signals reflected from the front wall of the object, from the back and from the defect, but in reality there are more of them, since longitudinal and transverse sound waves, the speed of which is different, can pass through.

 To increase the reliability of measurements in known microscopes, an analog key is installed, which selects the signal at a predetermined point in time.

 However, if the sample is not flat or the defect is in different places, this method is not applicable, since the second signal can go beyond the "gate".

 In this microscope, at each scanning point, you can set narrow “gates” and, changing the delay time, determine the shape of all pulses and configure the gate to a given, for example, second pulse, provided that it is a pulse, or not to turn it on if it is not.

 If the defect is located close to the rear surface of the sample, the second and third signals merge, in this case they analyze their shape, which makes it possible to detect the defect. (56) 1. USSR author's certificate N 1105806, cl. G 01 N 29/06, 1980.

 2. USSR author's certificate N 1631408, cl. G 01 N 29/04, 1988.

Claims (1)

 ACOUSTIC MICROSCOPE containing a pulse generator, an acoustic transceiver installed to move relative to the surface of the sample, an information storage unit connected to a control and processing unit, to the output of which an information display unit is connected, as well as an analog-digital information input and output unit a converter and a digital-to-analog converter connected by communication buses to a control and processing unit, characterized in that often between the output of the divider you and an acoustic transceiver include a counter and amplifier-signal generator connected in series, as well as a memory block and a series amplifier-limiter, the input of which is connected to the communication line between the amplifier-driver and the acoustic transceiver, an amplifier with an adjustable gain, an analog switch, programmable DC component detector, adjustable gain video amplifier and storage unit and select ki, the output of which is connected to the input of the analog-to-digital converter, while the input of the pulse generator is connected to the second input of the counter, the second, third and fourth outputs of which are connected respectively to the second input of the storage and sampling unit, the second input of the analog-to-digital converter and the second key input , the output of the memory unit is connected to the control input of the frequency divider, and its inputs to the corresponding outputs of the control and processing unit and the fifth output of the counter, the control inputs of the amplifier with adjustable coefficients an amplification element and a video amplifier with an adjustable gain are connected to the corresponding inputs of the control and processing unit, and the control input of the detector with a programmable DC component shift is connected to the output of the digital-to-analog converter, while the pulse generator is made in the form of a series-connected crystal oscillator and a frequency divider.

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