JP4787914B2 - Sonic velocity measuring method, sonic velocity measuring apparatus, and ultrasonic image inspection apparatus - Google Patents

Description

  The present invention relates to a sound speed measuring method, a sound speed measuring apparatus, and an ultrasonic image inspection apparatus that measure the speed of sound in an inspection object using ultrasonic waves.

  The size of the site to be excised during surgery should be kept as small as possible considering the burden on the patient after surgery. However, if part of the affected area remains without being excised, there is a problem that the disease will recur. is there. For this reason, it is necessary to sample a specimen (living tissue) from the remaining part after excision and confirm that there is no spread of the affected part. Currently, this operation is performed by staining a section of the extracted biological tissue and observing it with an optical microscope. Histologically confirmed diagnosis is a diagnosis that confirms that the affected area has not spread in the specimen based on pathological findings, but it is used for postoperative confirmation because it takes several days to stain the section. .

  During the operation, it is required to determine in a short time that no affected area remains before suturing. For this reason, a method such as “tissue rapid diagnosis” in which a special dye is used for staining in a short time to confirm that the affected area has not spread in the specimen portion has been put into practical use. However, this rapid tissue diagnosis also takes about one hour, and the operation is interrupted during this time. Therefore, as an alternative method, observation of a sound velocity image using ultrasonic waves has been proposed. That is, when a sound velocity image is obtained by ultrasonic waves, it is possible to observe a living tissue without using a staining method. For this reason, the development of products using an ultrasonic microscope as a diagnostic apparatus for performing a tissue definitive diagnosis is in progress.

  Specifically, in a conventional ultrasonic microscope, the properties of a living tissue are observed by using a single-frequency burst wave and analyzing the intensity and phase of the reflected ultrasonic signal. However, such an ultrasonic microscope has a problem that it takes a long time to measure an ultrasonic signal. In addition, since an analog system such as an oscillator and a measurement system having sufficient accuracy and stability is required, there is a problem that the apparatus becomes large and complicated.

  As means for solving these problems and enabling intraoperative diagnosis, the present inventors have already proposed a pulse excitation type ultrasonic microscope (see, for example, Non-Patent Document 1 and Patent Document 1). In observation using this pulse excitation type ultrasonic microscope, the tissue is cut out from a living tissue, a frozen section 41 having a thickness of several μm is prepared using the tissue, and is first fixed on a glass substrate 42 (see FIG. 15). . Then, the transducer 43 is excited by a pulse wave to output an ultrasonic wave So, and the ultrasonic wave So is irradiated onto the frozen section 41 through a medium 44 such as water. The combined wave of the reflected wave Sa on the tissue surface and the reflected wave Sb on the glass substrate 42 (tissue back surface) is received by the transducer 43. Further, the received wave is subjected to Fourier transform and compared with direct reflection from the substrate 42 to obtain an intensity and phase spectrum.

By the way, in the conventional method using a burst wave, it is necessary to measure the frequency by switching the frequency at the same measurement point and observe the interference between the reflection on the tissue surface and the reflection on the back surface. On the other hand, the pulse excitation type ultrasonic microscope has an advantage that it can be calculated by one measurement. If the frequency of the minimum point of the signal intensity obtained by this measurement is f _m and the phase at that time is φ _m , the reflection from the tissue surface and the back surface has an opposite phase at the minimum point. That is, at the minimum point, the reflection from the tissue surface is advanced in phase by (2n−1) π from the reflection from the back surface, and becomes φ _m + (2n−1) π (n is a natural number). Therefore, when the thickness of the tissue is d and the sound velocity of water is C ₀ ,

が成立している。

Is established.

  Therefore, the tissue thickness d is obtained as in the following equation.

Further, since the phase difference between the wave that has passed the distance 2d at the tissue sound speed C and the wave that has passed at the sound speed C ₀ of water is φ _m ,

となり、次式のように組織音速Ｃが求まる。

Thus, the tissue sound velocity C is obtained as in the following equation.

  Thus, a two-dimensional sound velocity image is obtained by two-dimensionally scanning the ultrasonic irradiation point while measuring the tissue sound velocity C.

  By the way, in the above-mentioned ultrasonic microscope, the frozen section 41 is placed on a glass substrate 42, and the glass substrate 42 is placed on an XY stage 45 which is a two-dimensional scanning means. For this reason, the relationship between the transducer 43, the glass substrate 42, and the frozen section 41 is not necessarily in a directly-facing relationship, and a slight inclination may occur. If this inclination is not zero, the thickness d and the tissue sound velocity C of the frozen section 41 cannot be accurately calculated, and a slight measurement error occurs. Due to the influence of this error, it becomes difficult to perform more precise and detailed image diagnosis.

As a countermeasure, the present inventors have proposed a method for calculating the thickness d of the frozen section 41 and the tissue sound velocity C by calculating the inclination amount of the glass surface in the glass substrate 42 and correcting the position of the glass surface. (For example, refer to Patent Document 2). Specifically, the measurer visually confirms a portion (glass surface) where the surface of the glass substrate 42 is exposed, and designates three points at an appropriate interval from the glass surface. Thereby, ultrasonic waves are irradiated to those three points in the ultrasonic microscope, and the plane equation (Z = ax + by + c) of the glass surface is calculated based on the reflected waveform. Thereafter, the thickness d of the frozen section 41 is corrected using the coefficients a, b, and c of the plane equation, and the tissue sound velocity C is obtained from the thickness d.
JP 2004-294189 A JP 2005-291827 A “Medical Ultrasound: Pulse Excitation Ultrasonic Sonic Microscope” (“Ultrasonic TECHNO” VOL.15 No.6 (November 11-12, 2003) (101-105 pages), published by Nihon Kogyo Shuppansha)

  However, in the above-described ultrasonic microscope, when the XY stage 45 is scanned, the stage moves up and down slightly, depending on the mechanical accuracy of the driving means. In particular, when the sonic stage generation process is performed in a short time by increasing the scanning speed of the XY stage 45, the vertical movement (backlash in the Z direction) of the XY stage 45 may be about 0.5 μm. The above-described tilt correction of the glass surface in Patent Document 2 is to obtain the tissue sound speed on the assumption that the glass surface is a flat surface, and the vertical movement of the XY stage 45 cannot be corrected. Therefore, a vertical error of about 0.5 μm causes a measurement error of about 100 m / s as the tissue sound speed.

  The conventional ultrasonic microscope has been devised to suppress the vertical movement by using a linear motor as the driving means of the XY stage 45, but it is difficult to completely eliminate the vertical movement. Further, even when the surface of the drive rail of the XY stage 45 is mirror-finished, unevenness of about 0.1 μm remains, so that an error that cannot be ignored as the tissue sound speed occurs. Furthermore, in order to make the drive of the XY stage 45 smooth, an effort has been made to apply lubricating oil on the drive rail. However, even in that case, the oil thickness varies, so the XY stage 45 The stage 45 is moved up and down.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a sound speed measuring method and a sound speed measuring apparatus capable of correcting a backlash in the Z direction of a two-dimensional scanning device and reducing measurement errors. It is to provide. Another object is to provide an ultrasonic image inspection apparatus capable of accurately displaying a sound velocity image of an inspection object and appropriately inspecting the inspection object.

  In order to solve the above-mentioned problem, in the invention according to claim 1, using a pulse excitation type ultrasonic microscope, the surface of the object to be inspected placed on the sample placing plate is irradiated with ultrasonic waves, A sound velocity measuring method for obtaining a thickness of an object to be inspected based on reflected waves from a front surface and a back surface of the object to be inspected, and for obtaining a sound speed of the object to be inspected based on the thickness, wherein the ultrasonic irradiation A step of two-dimensionally scanning a point in the X direction and the Y direction by a two-dimensional scanning device, and determining a non-mounting surface of the inspection object on the sample mounting plate based on the intensity of the reflected wave of the ultrasonic wave And correction data for correcting the distance difference from the reference point due to the backlash in the Z direction during the ultrasonic scanning by the two-dimensional scanning device based on the reflected wave of the ultrasonic wave on the non-mounting surface And a step based on the correction data. The seek Z direction distance difference, the sound speed measuring method characterized by comprising the steps of obtaining by calculation the speed of sound of the object to be inspected in view of its distance difference and its gist Te.

  According to the first aspect of the present invention, the surface of the object to be inspected is irradiated with ultrasonic waves using the pulse excitation type ultrasonic microscope, and the surface and the back surface of the object to be inspected are irradiated. The thickness of the object to be inspected is determined based on the reflected wave from the sound wave, and the sound velocity of the object to be inspected is determined based on the thickness. In this pulse excitation type ultrasonic microscope, when an ultrasonic wave is scanned two-dimensionally in the X direction and the Y direction by a two-dimensional scanning device, a slight backlash in the Z direction occurs. As a countermeasure, in the present invention, an ultrasonic irradiation point is two-dimensionally scanned in the X direction and the Y direction by a two-dimensional scanning device, and based on the intensity of the reflected wave of the ultrasonic wave, A non-mounting surface of the object to be inspected is determined, and correction data for correcting the backlash in the Z direction is obtained by calculation based on the reflected wave of the ultrasonic wave on the non-mounting surface. Then, a distance difference in the Z direction is obtained based on the correction data, and the sound speed of the object to be inspected is calculated based on the distance difference. In this way, it is possible to correct minute rattling in the Z direction, which was difficult with mechanical correction, and to obtain the sound speed more accurately.

  As the sample mounting plate, it is preferable to use a general preparation such as a glass substrate. When a living tissue or the like as an object to be inspected is placed on this glass substrate and the sound velocity is measured, the acoustic impedance of the crow substrate is larger than that of the living tissue, so that the reflected wave reflected on the non-mounting surface The intensity is greater than the reflected wave in the living tissue. In this case, the position at which the intensity of the reflected wave is maximized by two-dimensionally scanning the glass substrate with ultrasonic waves can be determined as the position on the non-mounting surface. And it can determine with the area | region where the reflected waveform approximated to the reflected waveform of the ultrasonic wave in the position where the intensity | strength of a reflected wave becomes the maximum is obtained as a non-mounting surface.

  According to a second aspect of the present invention, in the first aspect, when one or more measurement points on the X-direction scanning line are on the non-mounting surface, the X-direction scanning is performed on the non-mounting surface. The height of a plurality of measurement points on the line is measured for each scanning line, the average value for each scanning line is obtained as correction data in the Y direction, and the measurement point on the scanning line in the Y direction is not mounted. When there is one or more on the surface, the height of a plurality of measurement points on the scanning line in the Y direction on the non-mounting surface is measured for each scanning line, and the average value for each scanning line is calculated in the X direction. The gist is that the correction data is obtained.

  According to the second aspect of the present invention, when there are one or more measurement points on the scanning line in the X direction on the non-mounting surface, the heights of the plurality of measurement points on the scanning line in the X direction are It is measured for each scanning line, and an average value for each scanning line is obtained as correction data in the Y direction. Further, when there are one or more measurement points on the non-mounting surface on the Y-direction scanning line, the heights of the plurality of measurement points on the Y-direction scanning line are measured for each scanning line, and the scanning line An average value for each is obtained as correction data in the X direction. In this case, based on the correction data in the X direction and the correction data in the Y direction, the distance difference in the Z direction (height from the reference point) of the predetermined measurement point can be obtained. Further, since the correction data is obtained as an average value of the heights of a plurality of measurement points, the reliability of the data can be improved as compared with the case where the correction data is obtained from one measurement point.

  According to a third aspect of the present invention, in the second aspect, when all the measurement points on the scanning line in the X direction are on the inspection object, a plurality of measurement points on the non-mounting surface are measured. Using the reflected wave, the coefficient of the plane equation of the non-mounting surface is calculated, the correction data in the Y direction is obtained based on the coefficient of the plane equation, and all the measurement points on the scanning line in the Y direction are If it is on the object to be inspected, using the reflected waves from a plurality of measurement points on the non-mounting surface, calculate the coefficient of the plane equation of the non-mounting surface, and based on the coefficient of the plane equation The gist is that the correction data in the X direction is obtained.

  When there are no measurement points on the scanning line on the non-mounting surface, that is, when all the measurement points on the scanning line are on the object to be inspected, the correction data is obtained by the method of claim 2. I can't. Therefore, as in the invention described in claim 3, when all the measurement points on the scanning line in the X direction are on the inspection object, reflected waves from a plurality of measurement points on the non-mounting surface are used. Then, the coefficient of the plane equation of the non-mounting surface is calculated, and correction data in the Y direction is obtained based on the coefficient of the plane equation. Further, when all the measurement points on the scanning line in the Y direction are on the object to be inspected, the reflected wave from a plurality of measurement points on the non-mounting surface is used to calculate the plane equation of the non-mounting surface. A coefficient is calculated, and correction data in the X direction is obtained based on the coefficient of the plane equation. Then, based on the correction data in the X direction and the correction data in the Y direction, a distance difference in the Z direction at a predetermined measurement point can be obtained.

  The invention according to claim 4 uses a pulse excitation type ultrasonic microscope to irradiate the surface of the inspection object placed on the sample mounting plate with ultrasonic waves, and from the surface and the back surface of the inspection object. A sound speed measuring device that obtains the thickness of an object to be inspected based on the reflected wave and obtains the sound speed of the object to be inspected based on the thickness of the object. Two-dimensionally scanning the ultrasonic irradiation point in two directions in the X direction and the Y direction, and an ultrasonic transducer that receives the reflected wave from the inspection object and converts it into an electrical signal. A scanning device; signal intensity detecting means for detecting the intensity of the reflected wave based on the signal converted by the ultrasonic transducer; and an object to be inspected on the sample mounting plate based on the intensity of the reflected wave of the ultrasonic wave. Determining means for determining a non-mounting surface; and Correction data calculation means for calculating correction data for correcting a distance difference from a reference point due to backlash in the Z direction during ultrasonic scanning by the two-dimensional scanning device based on reflected ultrasonic waves A sound speed measuring device comprising: a sound speed calculating means for determining a distance difference in the Z direction based on the correction data, and calculating a sound speed of the inspection object in consideration of the distance difference. And

  According to the fourth aspect of the present invention, the ultrasonic transducer is pulse-excited so that the ultrasonic wave is irradiated toward the inspection object, and the ultrasonic irradiation point is set in the X direction and the Y direction by the two-dimensional scanning device. It is scanned two-dimensionally in the direction. At this time, the reflected wave from the object to be inspected is received by the ultrasonic transducer and converted into an electric signal, and the intensity of the reflected wave is detected based on the electric signal by the signal intensity detecting means. Then, the non-mounting surface of the inspection object on the sample mounting plate is determined based on the intensity of the reflected wave of the ultrasonic wave by the determining means. Further, the correction data calculating means calculates correction data for correcting rattling in the Z direction during ultrasonic scanning by the two-dimensional scanning device, based on the reflected ultrasonic wave on the non-mounting surface. Then, the sound speed calculation means determines a distance difference in the Z direction based on the correction data, and calculates the sound speed of the object to be inspected based on the distance difference. In this way, it is possible to correct minute rattling in the Z direction, which was difficult with mechanical correction, and to obtain the sound speed more accurately. Further, since no mechanical correction means is required, it is possible to avoid an increase in the size of the sound speed measuring device.

  The invention according to claim 5 is the first measurement point determination means for determining whether or not there are one or more measurement points on the scanning line in the X direction on the non-mounting surface in claim 4, The gist of the invention is to include second measurement point determination means for determining whether or not there are one or more measurement points on the Y-direction scanning line on the non-mounting surface.

  According to the fifth aspect of the present invention, it is determined by the first measurement point determination means whether or not there are one or more measurement points on the scanning line in the X direction on the non-mounting surface. When it is determined that there are one or more measurement points on the non-mounting surface, correction data in the Y direction is obtained by the method according to claim 2, and there is no measurement point on the non-mounting surface. If it is determined, correction data in the Y direction is obtained by the method according to claim 3. Further, it is determined by the second measurement point determination means whether or not there are one or more measurement points on the non-mounting surface on the scanning line in the Y direction. When it is determined that there are one or more measurement points on the non-mounting surface, correction data in the X direction is obtained by the method according to claim 2, and there is no measurement point on the non-mounting surface. Is determined, X direction correction data is obtained by the method according to claim 3.

  The invention according to claim 6 displays the sound velocity image, the sound velocity measuring device according to claim 4, image generation means for performing a process of generating a sound velocity image based on the sound velocity of the inspection object, and the sound velocity image. The gist of the ultrasonic image inspection apparatus is characterized by comprising a display device for the purpose.

  According to the invention described in claim 6, processing for generating a sound speed image by the image generating means is performed based on the sound speed of the object to be inspected obtained by the sound speed measuring device according to claim 4, A sound velocity image of the inspection object is displayed on the display device. If it does in this way, the sound speed image of a to-be-inspected object can be displayed correctly, and a to-be-inspected object can be test | inspected appropriately.

  As described in detail above, according to the first to fifth aspects of the present invention, the sound speed measurement method and the sound speed can be reduced by correcting the backlash in the Z direction of the two-dimensional scanning device, thereby reducing the sound speed measurement error. A measuring device can be provided. According to the invention described in claim 6, it is possible to provide an ultrasonic image inspection apparatus capable of accurately displaying a sound velocity image of an inspection object and appropriately inspecting the inspection object. it can.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an ultrasonic image inspection apparatus as a sound velocity measuring apparatus.

  As shown in FIG. 1, the ultrasonic image inspection apparatus 1 includes a pulse excitation type ultrasonic microscope 2, an A / D board 3, and a personal computer (personal computer) 4.

  The ultrasonic microscope 2 includes a pulse generation circuit 11, a transmission / reception separation circuit 12, a reception circuit 13, a transducer 14, an XY stage 15, an encoder (ENC) 16, controllers 17X and 17Y, and a drive. Motors 18X and 18Y are provided.

  The transducer 14 includes a thin film piezoelectric element 14a made of zinc oxide and an acoustic lens 14b made of sapphire rod. The thin film piezoelectric element 14a vibrates by an excitation pulse generated by the pulse generation circuit 11, and ultrasonic waves in a predetermined frequency band are generated by the acoustic lens. 14b. The ultrasonic waves in the acoustic lens 14b are converged in a conical shape, and are focused on the surface of the glass substrate 20 as a sample mounting plate via a medium 19 such as water. As the transducer 14, a transducer having a diameter of 1.2 mm, a focal length of 1.5 mm, a center frequency of 80 MHz, and a bandwidth of 50 to 105 MHz (-6 dB) is used.

  Further, an XY stage 15 as a two-dimensional scanning device is provided below the transducer 14, and a glass substrate 20 is fixed on the stage 15. Then, a biological tissue 21 as an inspection object is placed on the upper surface of the glass substrate 20. The living tissue 21 is a frozen section (living tissue section) sliced to a thickness of about several μm (usually 4 μm to 10 μm).

  The XY stage 15 includes stages 15X and 15Y for moving the living tissue 21 two-dimensionally, and motors 18X and 18Y for driving the stages 15X and 15Y. Linear motors are used as the motors 18X and 18Y.

  Controllers 17X and 17Y are connected to the motors 18X and 18Y, respectively, and the motors 18X and 18Y are driven in response to the drive signals of the controllers 17X and 17Y. By driving these motors 18X and 18Y, the X stage 15X is continuously scanned (continuous feed), and the Y stage 15Y is controlled to be intermittent feed. With this control, the XY stage 15 can be scanned at high speed.

  In the present embodiment, an encoder 16 is provided corresponding to the X stage 15X, and the encoder 16 detects the scanning position of the X stage 15. Specifically, when a scanning range (for example, a range of 2.4 mm × 2.4 mm) is divided into 300 × 300 measurement points (pixels), 300 in one scanning in the X direction (horizontal direction). Divided. Then, the position of each measurement point is detected by the encoder 16 and taken into the personal computer 4. The personal computer 4 generates a drive control signal in synchronization with the output of the encoder 16, and supplies the drive control signal to the controller 17X. The controller 17X drives the motor 18X based on this drive control signal. Further, the controller 17Y drives the motor 18Y when the scanning of one line in the X direction is completed based on the output signal of the encoder 16, and moves the Y stage 15Y by one pixel in the Y direction.

  Further, the controller 17X generates a trigger signal in synchronization with the drive control signal and supplies it to the pulse generation circuit 11. As a result, the pulse generation circuit 11 generates an excitation pulse at a timing synchronized with the trigger signal. The excitation pulse is supplied to the transducer 14 via the transmission / reception wave separation circuit 12, and ultrasonic waves are emitted from the transducer 14.

  FIG. 2 is a plan view of the XY stage 15 as seen from the transducer 14 side. As shown in FIG. 2, by performing reciprocal scanning in the X direction by the X stage 15X and scanning in the Y direction by the Y stage, ultrasonic waves are two-dimensionally applied to the living tissue 21 on the glass substrate 20. Scanned.

  FIG. 3 shows an example of the ultrasonic scanning range R in the present embodiment. That is, the ultrasonic scanning range R is set so as to include a portion (glass surface 20 a) where the surface of the glass substrate 20 is exposed in addition to the biological tissue 21. Then, scanning is started from the position of the upper left corner of the scanning range R, and scanning is sequentially performed two-dimensionally in the X direction and the Y direction as indicated by arrows.

  The thin film piezoelectric element 14a of the transducer 14 shown in FIG. 1 is an ultrasonic transducer that is also used for transmitting and receiving waves, and converts ultrasonic waves (reflected waves) reflected by the living tissue 21 into electrical signals. The reflected wave signal is supplied to the detection circuit 28 of the A / D board 3 via the transmission / reception wave separation circuit 12 and the reception circuit 13.

  The detection circuit 28 is a circuit for detecting a reflected wave of ultrasonic waves, and includes a gate circuit, a delay circuit, an arithmetic circuit, a BPF (band pass filter), a peak hold circuit, and the like (not shown). The detection circuit 28 of the present embodiment detects a signal intensity of the reflected wave signal, and a first detector 28a that extracts the reflected wave signal of the glass surface 20a or the living tissue 21 from the reflected wave signal received by the transducer 14. And a second detector 28b as signal intensity detecting means. The ultrasonic waves are repeatedly reflected between the transducer 14 and the glass surface 20a or the living tissue 21. Therefore, the first detection unit 28a of the detection circuit 28 is configured to extract the reflected wave signal obtained first. The second detector 28b detects the signal strength of the reflected wave signal. Based on a control signal (not shown) from the personal computer 4, the detection circuit 28 inputs the reflected wave signal extracted by the first detection unit 28a to the A / D conversion circuit 29, or the second detection unit 28b. The detected signal intensity is input to the A / D conversion circuit 29.

  The personal computer 4 includes a CPU 31, interfaces (I / F) 32 and 33, a fast Fourier transform circuit (FFT) 34, a memory 35, a storage device 36, an input device 37, and a display device 38, which are connected via a bus 39. Are connected to each other.

  The CPU 31 executes a control program using the memory 35 and controls the entire apparatus in an integrated manner. The control program includes a program for controlling two-dimensional scanning by the XY stage 15, a program for calculating tissue sound speed, and the like.

  The interface 32 is a communication port (for example, a USB port) for taking in transfer data (such as a reflected wave signal after A / D conversion) from the A / D board 3. The interface 33 is an input / output port for outputting a drive control signal to the controller 17X and taking in an output signal of the encoder 16.

  The fast Fourier transform circuit 34 is a circuit that performs a Fourier transform process for obtaining a frequency component of the reflected wave signal based on the reflected wave signal input from the A / D board 3.

  The display device 38 is, for example, a color display such as an LCD or CRT, and is used to display a sound velocity image of the biological tissue 21 and an input screen for various settings. The input device 37 is a keyboard, a mouse device, or the like, and is used for inputting requests, instructions, and parameters from the user.

  The storage device 36 is a magnetic disk device or an optical disk device, and the storage device 36 stores a control program and various data. The CPU 31 transfers a program and data from the storage device 36 to the memory 35 in accordance with an instruction from the input device 37, and sequentially executes it. The program executed by the CPU 31 may be a program stored in a storage medium such as a memory card, a flexible disk, or an optical disk, or a program downloaded via a communication medium. At the time of execution, the program is installed in the storage device 36 and used. To do.

  In the ultrasonic microscope 2, when the XY stage 15 is scanned, the XY stage 15 is moved up and down by mechanical accuracy of the motors 18X and 18Y and the backlash is generated in the Z direction. Therefore, in the present embodiment, the sound velocity of the living tissue 21 is accurately measured by correcting and calculating the backlash in the Z direction.

  This vertical movement of the XY stage 15 is reproducible when scanned in the same direction of the X direction or the Y direction. Therefore, in the present embodiment, the XY stage 15 is moved up and down based on the reflected wave from the region where the surface of the glass substrate 20 is exposed, that is, the glass surface 20a which is the non-mounting surface of the living tissue 21. Correction data for correcting is obtained by calculation. Based on the correction data, the position of the glass surface on the back side of the tissue is estimated, and the sound speed of the living tissue 21 is corrected and calculated.

  Specifically, in the scanning range R of FIG. 3, ultrasonic waves are scanned two-dimensionally, the glass surface 20a is determined based on the reflected wave signal, and reflection from a plurality of measurement points on the glass surface 20a. Correction data is obtained based on the wave signal.

  Here, a method for automatically extracting each measurement point of the glass surface 20a in the scanning range R will be described.

  Since the acoustic impedance of the glass substrate 20 is larger than that of the living tissue 21, the signal intensity of the reflected wave on the glass surface 20a where the surface of the glass substrate 20 is exposed is stronger than the reflected wave from the living tissue 21. Therefore, in the present embodiment, whether the reflection is from the living tissue 21 or the reflection from the glass surface 20a is determined based on the signal intensity of the reflected wave at each measurement point.

  Here, in order to prevent erroneous determination due to the influence of noise or the like, as shown in FIG. 4, the scanning range R is set to a predetermined square area B smaller than that (in this embodiment, 10 × 10 measurement points). A block composed of P0, P1, P2,. And based on the average value of the signal intensity of the reflected wave in each area | region B, it determines with the position where the signal intensity becomes the maximum being a position on the glass surface 20a. Further, the measurement point determined to be the position on the glass surface 20a is set as a reference point, and the reflected waveform at the reference point is set as a reference waveform. Then, the reflected waveform at each measurement point obtained by two-dimensional scanning with ultrasonic waves is compared with the reference waveform, and the region where the approximate reflected waveform is obtained is determined to be the glass surface 20a. Each measurement point on the surface 20a is extracted.

  Here, the reflected waves at any two points on the glass surface 20a have the same waveform (reference waveform). However, if the XY stage 15 moves up and down during the ultrasonic scanning, the distance from the transducer 14 differs, and therefore, as shown in FIG. 5, between the reference waveform Sr and another reflected waveform Sx on the glass surface 20a. A phase difference occurs. Therefore, as shown in FIG. 6, the intensity spectrum obtained by normalizing the reflected waveform Sx on the glass surface 20a with the reference waveform Sr takes a value close to 1 at all frequencies.

  On the other hand, since the acoustic impedance between the biological tissue 21 and water is close where the biological tissue 21 is present, the reflected waveform Sy at the biological tissue 21 is compared to the reference waveform Sr at the glass surface 20a as shown in FIG. Get smaller. That is, as shown in FIG. 8, the intensity spectrum obtained by normalizing the reflected waveform Sy from the living tissue 21 with the reference waveform Sr becomes a value smaller than 1. Further, since the reflected waveform Sy at the biological tissue 21 is obtained by interference between the reflection on the tissue surface and the reflection on the back surface, the intensity spectrum does not become flat.

  Therefore, by comparing the reflected waveform at each measurement point obtained by two-dimensional scanning with ultrasonic waves with the intensity spectrum of the reference waveform, it can be determined whether or not the waveform approximates the reference waveform. And when it is an approximate waveform, it determines with the measurement point being in the position on the glass surface 20a. By this determination, each measurement point on the glass surface 20a within the scanning range R can be automatically extracted.

  Next, a method for calculating correction data for correcting the vertical movement (backlash in the Z direction) of the XY stage 15 during ultrasonic scanning will be described.

  In the present embodiment, first, each reflected wave signal is obtained by irradiating each measurement point with ultrasonic waves at each measurement point P0, P1, P2,... Extracted as a position on the glass surface 20a. Then, Fourier transform processing is performed in order to obtain frequency components of these reflected wave signals, and using the respective Fourier transform outputs F0, F1, F2,..., A normalized spectrum (F1 / F0) based on the measurement point P0 is used. ), (F2 / F0),...

From the complex plane related to the normalized spectrum (the relationship of the phase φ with respect to the frequency), the time difference Δt1 (= φ / 2πf (= φ / 2πf), where the reference point P0 and the measurement point P1 are caused by the backlash in the Z direction of the XY stage 15. f is the center frequency of the ultrasonic wave)). Then, using this time difference Δt1 and the sound velocity C0 of the medium 19 (specifically water), the value (height) Z1 (= Δt1 × C ₀ ) in the Z direction of the measurement point P1 with the reference point P0 as the reference position. ) Is required. Similarly, the time differences Δt2,... Between the reference point P0 and the other measurement points P2,... Are obtained, and the heights Z2,.

Then, a height of the average of a plurality of measurement points in the X direction of scanning the line Lx in the glass surface 20a for each scanning line Lx, correction data b ₁ corresponding to the average value in the _{Y-coordinate,} b _2, .., B _j ,... _Are stored in the memory 35 (see FIG. 9). Similarly, an average value of the heights of a plurality of measurement points on the scanning line Ly in the Y direction on the glass surface 20a is obtained for each scanning line Ly, and the average value is corrected data a ₁ , corresponding to the coordinates in the X direction. are stored in the memory 35 as a ₂ ,..., a _i ,.

As shown in FIG. 11, the backlash in the Z direction of the XY stage 15 is reproducible when scanned in the same direction of the X direction or the Y direction. Therefore, the height Z in the Z direction at an arbitrary measurement point P (x _i , y _j ) is approximated by the following equation (5) using two curve equations in the X direction and the Y direction (compound curve approximation). can do.

Z (x _i , y _j ) = f (x _i ) + g (y _j ) (5)

Here, when f (x _i ) = a _i and g (y _j ) = b _j are set, the square error can be defined by the following equation (6).

  The conditions for minimizing this are:

となる。ただし、Ｎ_ｉは、Ｘ座標がｘ_ｉである参照点（ガラス面２０ａ上の測定点）の総数、Ｍ_ｊは、Ｙ座標がｙ_ｊである参照点（ガラス面２０ａ上の測定点）の総数である。上式（７），（８）により、

It becomes. However, _{N i} is the total number of the reference point X coordinates are _{x i} (measurement point on the glass surface 20a), _{M j} is the reference point Y coordinates are _{y j} (measured points on the glass surface 20a) It is the total number. From the above formulas (7) and (8),

となる。この行列式（９）を解くことにより、Ｘ方向の補正データａ_ｉとＹ方向の補正データｂ_ｊとが求められる。

It becomes. By solving the determinant (9), correction data a _i in the X direction and correction data b _{j in the} Y direction are obtained.

These correction data a _i and b _j can be obtained based on the reflected wave from the glass surface 20a when one or more measurement points on the scanning lines L _x and L _{y are} on the glass surface 20a. However, as shown in FIG. 9, on the scanning line Lx in the X direction located in the lower region R0 of the scanning range R, all the measurement points are on the living tissue 21, and therefore on the scanning line. The average value (correction data) of the height cannot be obtained based on the reflected wave from the glass surface 20a. In this case, similarly to Patent Document 2, a plane equation (Z = ax + by + c) of the glass surface 20a is calculated using reflected waves from three measurement points on the glass surface 20a. Then, correction data corresponding to the Y coordinate of the lower region R0 of the scanning range R is obtained using the coefficients a, b, and c of the plane equation.

  When the scanning range R as shown in FIG. 12 is set, all measurement points are on the living tissue 21 on the Y-direction scanning line Ly located in the region R1 on the right side of the scanning range R. Therefore, the average value of height (correction data) cannot be obtained based on the reflected wave from the glass surface 20a. Also in this case, each coefficient of the plane equation of the glass surface 20a is calculated, and correction data in the X direction is obtained using each coefficient of the plane equation.

Then, using the correction data a _i and b _j in the X direction and the Y direction obtained in this way, the height at each measurement point in the living tissue 21 can be estimated. In addition, the height of each measurement point calculated | required here becomes a value (distance difference) including the amount of inclination of the glass surface 20a in addition to the vertical movement of the XY stage 15. FIG.

  Next, a method for obtaining the sound speed of the living tissue 21 will be described.

  Since the reflected wave signal at a predetermined measurement point in the biological tissue 21 is shifted by a phase corresponding to the height (distance difference) in the Z-axis direction at the measurement point, the biological component is corrected by correcting the phase. The thickness d and the sound velocity C of the tissue 21 are accurately obtained.

More specifically, a distance difference Δz in the Z direction corresponding to the X coordinate and Y coordinate of the measurement point is calculated using the correction data a _i and b _j , and the distance difference Δz is substituted into the following equation (10). A phase shift amount Δφ _m is obtained.

However, f _m is the frequency of the local minimum point of the signal strength.

By obtaining a phase φ _m obtained by correcting the deviation amount Δφ _m and substituting it into the above formulas (2) and (4), the final thickness d obtained by correcting the distance difference Δz caused by the backlash in the Z direction is obtained. The speed of sound C is required.

  Next, an example of processing executed by the CPU 31 to generate a sound velocity image of the living tissue 21 in the present embodiment will be described using the flowcharts of FIGS. 13 and 14. FIG. 13 is a process for calculating correction data, and FIG. 14 is a process for generating a sound speed image in consideration of the backlash in the Z direction of the XY stage 15.

  First, the CPU 31 outputs control signals to drive the motors 18X and 18Y by the controllers 17X and 17Y to start two-dimensional scanning by the XY stage 15, and based on the output of the encoder 16, the coordinate data of the measurement point To get. At this time, when the excitation pulse is supplied to the transducer 14, ultrasonic waves are emitted from the transducer 14, and the signal intensity of the reflected wave is detected by the second detection unit 28 b of the detection circuit 28. The CPU 31 takes in the digital data converted by the A / D conversion circuit 29 via the interface 32, and stores the data in the memory 35 in association with the coordinate data as the signal intensity of the reflected wave at each measurement point ( Step 100).

  In step 100, after obtaining the signal intensity of the reflected wave at all measurement points in the scanning range R, the measurement point having the highest signal intensity is extracted from each measurement point (step 110). In addition, in this step 110, an average value is calculated | required for every block B which consists of a measurement point of 10x10, and the arbitrary measurement point of the block B where the value becomes the maximum is used as a reference point in the position on the glass surface 20a. Extracted.

  The CPU 31 drives the XY stage 15 to a position corresponding to the reference point, and scans ultrasonic waves by the drive to obtain a reference waveform at the reference point (step 120). Here, when the ultrasonic wave is irradiated toward the reference point on the glass surface 20a, the reflected wave signal of the ultrasonic wave is extracted by the first detection unit 28a of the detection circuit 28, and then the A / D conversion circuit 29. Is converted into digital data. The CPU 31 takes in the reflected wave signal via the interface 32 and inputs it to the fast Fourier transform circuit 34. The fast Fourier transform circuit 34 performs a Fourier transform process for obtaining the frequency component of the reflected wave signal. The CPU 31 takes in the output (Fourier transform output) of the fast Fourier transform circuit 34 and stores it in the memory 35 as reference waveform data.

  The CPU 31 scans the ultrasonic waves two-dimensionally by driving the XY stage 15 and acquires the reflected wave signal at each measurement point (step 130). Again, the reflected wave signal at each measurement point is Fourier transformed by the fast Fourier transform circuit 34 and the Fourier transform output is stored in the memory 35 in association with the coordinate data of the measurement point.

  The CPU 31 as the determination means calculates the normalized spectrum data by normalizing the Fourier transform output at each measurement point with the reference waveform data, and the measurement point is on the glass surface 20a based on the normalized spectrum. It is determined whether it is a position. By performing this determination for all the measurement points, the CPU 31 extracts all the measurement points on the glass surface 20a and acquires the coordinate data of these measurement points (step 140).

  The CPU 31 as the correction data calculation means calculates correction data based on the extracted reflection waveform data at each measurement point. Specifically, the CPU 31 obtains a normalized spectrum for the extracted measurement point by calculating the ratio between the Fourier transform output of the reflected wave signal and the Fourier transform output of the reference waveform. Then, the CPU 31 obtains a time difference from the frequency component f and the phase component φ of the normalized spectrum, and calculates the height of the measurement point (distance difference in the Z direction) from the time difference and the known sound speed (specifically, the sound speed of water). ) Is calculated (step 150). Here, the heights of all the measurement points extracted as measurement points on the glass surface 20a are calculated.

Thereafter, the CPU 31 as the first measurement point determination means determines whether or not there are one or more measurement points on the scanning line Lx in the X direction on the glass surface 20a (step 160). For the scanning line Lx determined to have one or more measurement points on the glass surface 20a, the average value of the heights of the respective measurement points on the scanning line Lx is obtained for each scanning line Lx, and the average value is calculated as Y. The direction correction data b _j is stored in the memory 35 (step 170). Here, when there is one measurement point, the height is used as correction data. On the other hand, when it is determined that all the measurement points on the scanning line Lx in the X direction are on the living tissue 21, correction data corresponding to the Y coordinate of the scanning line Lx is obtained based on the plane equation of the glass surface 20a. Is stored in the memory 35 (step 180).

Next, the CPU 31 as the second measurement point determination means determines whether or not there are one or more measurement points on the scanning line Ly in the Y direction on the glass surface 20a (step 190). For the scanning line Ly determined to have one or more measurement points on the glass surface 20a, the average value of the height of each measurement point on the scanning line Ly is obtained for each scanning line Ly, and the average value is calculated as X The direction correction data b _j is stored in the memory 35 (step 200). Here, when there is one measurement point, the height is used as correction data. On the other hand, when it is determined that all the measurement points on the scanning line Ly in the Y direction are on the living tissue 21, correction data corresponding to the X coordinate of the scanning line Ly is obtained based on the plane equation of the glass surface 20a. Is stored in the memory 35 (step 210).

  After the process in FIG. 13 is completed, the CPU 31 starts the process in FIG.

  The CPU 31 outputs the control signal to drive the motors 18X and 18Y under the control of the controllers 17X and 17Y to start the two-dimensional scanning by the XY stage 15, and the coordinate data of the measurement point based on the output of the encoder 16 To get. (Step 300). At this time, when the excitation pulse is supplied to the transducer 14, ultrasonic waves are emitted from the transducer 14, and the reflected wave signal is detected by the first detection unit 28 a of the detection circuit 28.

  The CPU 31 takes in the detected reflected wave signal via the A / D conversion circuit 29 and the interface 32 and inputs the reflected wave signal to the fast Fourier transform circuit 34. The fast Fourier transform circuit 34 performs a Fourier transform process for obtaining the frequency component of the reflected wave signal. The CPU 31 takes in the output (Fourier transform output) of the fast Fourier transform circuit 34 and stores it in the memory 34 (step 310).

  CPU31 calculates | requires the distance difference of the Z direction corresponding to the coordinate data of a measurement point using the correction data calculated | required by the process of FIG. 13 (step 320).

  The CPU 31 as the calculation means calculates the thickness d of the living tissue 21 at the measurement point from the time difference between the reflected wave signal at the reference point and the reflected wave signal at the measurement point, the intensity of the reflected wave signal, the phase difference, and the like ( Step 330). At this time, in consideration of the distance difference at the measurement point, the influence due to the rattling in the Z direction is removed, and an accurate thickness d is calculated. Thereafter, the CPU 31 obtains the sound speed C at the measurement point from the calculated thickness d, and stores the sound speed C in the memory 35 in association with the coordinate data of the measurement point (step 340).

  The CPU 31 as the image generation means performs image processing for generating a sound speed image based on the calculated sound speed C (step 350). That is, the CPU 31 performs color modulation processing using the sound speed C, generates image data corresponding to the magnitude of the sound speed C, and stores the image data in the memory 35.

  The CPU 31 determines whether or not the processing at all measurement points has been completed and image data for one screen has been acquired (step 360). If all the data has not been acquired, the CPU 31 returns to step 300 and repeatedly executes the processing of steps 300 to 360. If all the data has been acquired, the CPU 31 transfers the data to the display device 38. Then, after the sound velocity image corresponding to the data is displayed, the processing of FIG.

  Therefore, according to the present embodiment, the following effects can be obtained.

  (1) According to the ultrasonic image inspection apparatus 1 of the present embodiment, the non-mounting surface of the living tissue 21 on the glass substrate 20, that is, the glass surface 20a where the substrate surface is exposed is based on the signal intensity of the reflected wave. Can be determined. Based on the reflected waves at a plurality of measurement points on the glass surface 20a, correction data for correcting the backlash in the Z direction of the XY stage 15 can be obtained. Then, a distance difference in the Z direction is obtained based on the correction data, and the sound speed of the living tissue 21 is calculated by calculation based on the distance difference. In this way, it is possible to correct minute rattling in the Z direction, which was difficult with mechanical correction, and to obtain the sound speed more accurately. A sound speed image is generated based on the sound speed and displayed on the display device 38. In this case, the sound velocity image of the living tissue 21 can be accurately displayed, and the living tissue diagnosis of the living tissue 21 can be performed appropriately. Furthermore, since the mechanical correction means for correcting the backlash in the Z direction is not necessary, the enlargement of the ultrasonic image inspection apparatus 1 can be avoided.

  (2) In the case of the ultrasonic image inspection apparatus 1 of the present embodiment, all measurement points on the glass surface 20a are extracted. When there are one or more measurement points on the scanning surface Lx in the X direction on the glass surface 20a, the heights of all the measurement points on the scanning line Lx in the X direction are measured for each scanning line. An average value for each line is obtained as correction data in the Y direction. When there are one or more measurement points on the glass surface 20a on the Y-direction scanning line Ly, the heights of all measurement points on the Y-direction scanning line Ly are measured for each scanning line, and scanning is performed. An average value for each line is obtained as correction data in the X direction. Thus, by obtaining correction data based on reflected waves at more measurement points, the calculation error can be reduced, and the distance difference in the Z direction can be obtained more accurately. As a result, the measurement accuracy of the sound speed of the living tissue 21 can be increased.

  (3) In the case of the present embodiment, when all the measurement points on the scanning line Lx in the X direction are on the living tissue 21, the glass surface is used by using the reflected waves from the three measurement points on the glass surface 20a. The coefficient of the plane equation 20a is calculated, and correction data in the Y direction can be obtained based on the coefficient of the plane equation. Even when all measurement points on the Y-direction scanning line Ly are on the living tissue 21, correction data in the X direction can be obtained based on the plane equation of the glass surface 20a.

  (4) In the case of the ultrasonic image inspection apparatus 1 according to the present embodiment, the scanning range is divided into regions made up of 10 × 10 measurement points, and the value is determined based on the average value of the signal intensity of the reflected wave in that region. It is determined that the region where the maximum value is the position on the glass surface 20a. In this way, it can be reliably prevented that the measurement point on the surface of the living tissue 21 is erroneously determined to be the position on the glass surface 20a due to the influence of noise or the like.

  (5) In the case of the ultrasonic image inspection apparatus 1 according to the present embodiment, the reflected waveform from the glass surface 20a is compared by comparing the intensity spectrum obtained by Fourier transforming the reflected wave signal at each measurement point. It is possible to accurately determine whether or not.

  In addition, you may change embodiment of this invention as follows.

  In the above embodiment, when the reference point on the glass surface 20a having the maximum signal intensity is detected, each measurement point on the glass surface 20a is extracted and correction data is calculated, the thickness d and sound speed of the living tissue 21 are calculated. The two-dimensional ultrasound scanning is performed at each processing timing such as when C is calculated, but the present invention is not limited to this. For example, when the storage capacity of the memory 35 built in the personal computer 4 is large, the reflected wave signal and the signal intensity data at each measurement point obtained by one two-dimensional scanning are all stored in the memory 34. Using these data, each processing such as detection of a reference point on the glass surface 20a, extraction of each measurement point on the glass surface 20a, calculation of correction data, calculation of the thickness d and sound velocity C of the living tissue 21 is performed. It may be configured to do. With this configuration, it is possible to reduce the processing time required for two-dimensional scanning of ultrasonic waves, so that it is possible to quickly generate a sound velocity image of the living tissue 21.

  In the above-described embodiment, correction data is calculated and the sound speed is obtained using the correction data. However, this calculation process can be changed as appropriate. For example, the correction data may be calculated after obtaining the sound speed including an error due to vertical movement, and the sound speed may be corrected using the correction data. In this case, the pre-correction and post-correction sound speed images are displayed on the display device 38 using the uncorrected sound speed and the corrected sound speed, and the superiority of the correction process is confirmed by comparing the sound speed images. be able to.

  In the above embodiment, when all the measurement points on the scanning line are on the biological tissue 21, the correction data is calculated by calculating the plane equation of the glass surface 20a based on the reflected waves of the three measurement points on the glass surface 20a. However, the plane equation of the glass surface 20a may be calculated based on the reflected waves at four or more measurement points.

  In the above-described embodiment, the configuration in which the ultrasonic irradiation point is scanned two-dimensionally by driving the XY stage 15 as a two-dimensional scanning device is adopted. A scanning device may be provided.

  In the above embodiment, the ultrasonic image inspection apparatus 1 is used to measure the speed of sound of the living tissue 21 as the object to be inspected. May be.

  In the above embodiment, the fast Fourier transform circuit 34 that performs the Fourier transform processing is provided in the personal computer 4, but may be provided in the external A / D board 3. Further, as the A / D board 3, a board that can be mounted inside the personal computer 4 may be used.

  In the ultrasonic image inspection apparatus 1 according to the above-described embodiment, the sound velocity image is obtained by color modulation. However, the sound velocity image may be visualized as a luminance-modulated sound velocity image.

  Next, in addition to the technical ideas described in the claims, the technical ideas grasped by the embodiment described above are listed below.

  (1) In Claim 1, it determines with the position where the intensity | strength of the said reflected wave becomes the maximum being a position on the said non-mounting surface, The sound speed measuring method characterized by the above-mentioned.

  (2) In the technical idea (1), it is determined that an area where a reflected waveform approximate to the reflected waveform of the ultrasonic wave at a position where the intensity of the reflected wave is maximum is obtained is the non-mounting surface. A method of measuring the speed of sound.

  (3) In any one of claims 1 to 4, the ultrasonic scanning range includes a non-mounting surface in which the surface of the sample mounting plate is exposed in addition to the surface of the inspection object. A sound velocity measuring method characterized by being set.

  (4) The ultrasonic image inspection apparatus according to claim 6, wherein the object to be inspected is a biological tissue, and a biological tissue diagnosis is performed based on a sound velocity image displayed on the display device.

  (5) In Claim 6, the image generation means generates image data color-modulated according to the calculated sound velocity of the object to be inspected, and color-coded according to the sound velocity according to the image data. An ultrasonic image inspection apparatus, wherein the sound speed image thus displayed is displayed on the display device.

1 is a schematic configuration diagram illustrating an ultrasonic image inspection apparatus according to an embodiment embodying the present invention. The top view of the XY stage seen from the transducer side. Explanatory drawing which shows the scanning range of an ultrasonic wave. Explanatory drawing which shows the block for calculating the average value of signal strength. Explanatory drawing which shows the reflected waveform on a glass surface. Explanatory drawing which shows the intensity spectrum of the reflected waveform in a glass surface. Explanatory drawing which shows the reflected waveform on the biological tissue surface. Explanatory drawing which shows the intensity spectrum of the reflected waveform on the biological tissue surface. Explanatory drawing for demonstrating the calculation method of the correction data corresponding to a Y coordinate. Explanatory drawing for demonstrating the calculation method of the correction data corresponding to a X coordinate. Explanatory drawing which shows the backlash of the Z direction of the XY stage at the time of ultrasonic scanning. Explanatory drawing which shows the scanning range of another ultrasonic wave. The flowchart which shows the calculation process of correction data. The flowchart which shows the production | generation process of a sound speed image. The schematic diagram which shows the measuring method in the conventional pulse excitation type ultrasonic microscope.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Ultrasonic image inspection apparatus as a sound velocity measuring device 2 ... Pulse excitation type ultrasonic microscope 14a ... Thin film piezoelectric element as an ultrasonic transducer 15 ... XY stage as a two-dimensional scanning device 20 ... As a sample mounting plate Glass substrate 20a ... Glass surface as non-mounting surface 21 ... Biological tissue as inspection object 28b ... Second detection unit 31 as signal intensity detection means 31 ... CPU as determination means, calculation means, and image generation means
38 ... Display device ΔZ ... Distance difference a ₁ , a ₂ , a _i ... Correction data in X direction b ₁ , b ₂ , b _j ... Correction data in Y direction Lx ... Scan line in X direction Ly ... Scan line in Y direction P0: Measurement point as reference point P1, P2: Measurement point

Claims (6)

Using a pulsed excitation type ultrasonic microscope, the surface of the inspection object placed on the sample mounting plate is irradiated with ultrasonic waves, and the inspection is performed based on the reflected waves from the front and back surfaces of the inspection object. A sound velocity measuring method for obtaining the thickness of an object and obtaining the sound velocity of the object to be inspected based on the thickness,
The ultrasonic irradiation point is scanned two-dimensionally in the X and Y directions by a two-dimensional scanning device, and the object to be inspected is not placed on the sample placement plate based on the intensity of the reflected wave of the ultrasonic wave. Determining a surface;
Based on the reflected wave of the ultrasonic wave on the non-mounting surface, correction data for correcting a distance difference from the reference point due to rattling in the Z direction during ultrasonic scanning by the two-dimensional scanning device is obtained by calculation. Steps,
Obtaining a distance difference in the Z direction based on the correction data, and calculating a sound speed of the inspection object in consideration of the distance difference. When there are one or more measurement points on the non-mounting surface on the X-direction scanning line, the height of the plurality of measurement points on the X-direction scanning line on the non-mounting surface is set as the scanning line. Measured every time, find the average value for each scanning line as correction data in the Y direction,
When there are one or more measurement points on the Y-direction scanning line on the non-mounting surface, the height of the plurality of measurement points on the Y-direction scanning line on the non-mounting surface is set as the scanning line. The sound speed measurement method according to claim 1, wherein measurement is performed every time, and an average value for each scanning line is obtained as correction data in the X direction. When all the measurement points on the scanning line in the X direction are on the inspection object, the plane equation of the non-mounting surface is obtained by using reflected waves from a plurality of measurement points on the non-mounting surface. The correction data in the Y direction is obtained based on the coefficient of the plane equation,
When all the measurement points on the scanning line in the Y direction are on the object to be inspected, the plane equation of the non-mounting surface is obtained using reflected waves from a plurality of measurement points on the non-mounting surface. The sound speed measurement method according to claim 2, wherein the correction coefficient in the X direction is obtained based on the coefficient of the plane equation. Using a pulsed excitation type ultrasonic microscope, the surface of the inspection object placed on the sample mounting plate is irradiated with ultrasonic waves, and the inspection is performed based on the reflected waves from the front and back surfaces of the inspection object. A sound velocity measuring device that obtains the thickness of an object and obtains the sound velocity of the object to be inspected based on the thickness,
An ultrasonic transducer that irradiates an ultrasonic wave toward the inspection object by being pulse-excited and receives a reflected wave from the inspection object and converts it into an electrical signal;
A two-dimensional scanning device that two-dimensionally scans the ultrasonic irradiation point in the X direction and the Y direction;
Signal intensity detection means for detecting the intensity of the reflected wave based on the signal converted by the ultrasonic transducer;
Based on the intensity of the reflected wave of the ultrasonic wave, determination means for determining the non-mounting surface of the inspection object on the sample mounting plate;
Based on the reflected wave of the ultrasonic wave on the non-mounting surface, correction data for correcting a distance difference from the reference point due to rattling in the Z direction during ultrasonic scanning by the two-dimensional scanning device is obtained by calculation. Correction data calculation means;
A sound speed measuring device, comprising: a sound speed calculation unit that calculates a distance difference in the Z direction based on the correction data, and calculates a sound speed of the inspection object in consideration of the distance difference. First measurement point determination means for determining whether or not there are one or more measurement points on the scanning line in the X direction on the non-mounting surface;
The sound velocity measurement according to claim 4, further comprising second measurement point determination means for determining whether or not there are one or more measurement points on the non-mounting surface on the scanning line in the Y direction. apparatus. A sound velocity measuring device according to claim 4, an image generating means for performing a process of generating a sound velocity image based on the sound velocity of the inspection object, and a display device for displaying the sound velocity image. A featured ultrasonic image inspection apparatus.

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