Thickness measuring device and thickness measuring method

Abstract

A thickness measurement device (100) includes an ultrasonic transmitter (110) configured to transmit an ultrasonic wave toward a measurement target (S), an ultrasonic receiver (120) configured to receive an ultrasonic wave reflected by the measurement target, a first extraction unit (214) configured to extract a first reflected wave reflected at a first surface of the measurement target from a received wave received by the ultrasonic receiver, a second extraction unit (216) configured to extract a plurality of candidates of a second reflected wave reflected at a second surface of the measurement target from the received wave, a coincidence degree calculation unit (218) configured to calculate a coincidence degree of the first reflected wave and each of the candidates, a candidate determination unit (220) configured to determine a candidate having the largest coincidence degree as the second reflected wave from among the plurality of candidates, and a thickness calculation unit (222) configured to calculate a thickness of the measurement target based on a reception time of the first reflected wave in the ultrasonic receiver and a reception time of the second reflected wave determined by the candidate determination unit.

Description

Technical Field

[0001] This disclosure relates to a thickness measuring apparatus and a thickness measuring method. This application claims priority based on Japanese Patent Application No. 2020-193499, filed on November 20, 2020, the contents of which are incorporated herein by reference. Background Technology

[0002] As a non-destructive technique for measuring the thickness of an object, ultrasonic technology is employed. In such a technique, ultrasonic waves are transmitted to the surface of the object, and the thickness of the object is measured based on the difference between the time when the surface-reflected wave is received and the time when the back-reflected wave propagates inside the object and is reflected on the back side (e.g., Patent Document 1).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent No. 2840656 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] In the prior art, as described in Patent Document 1, the wave with the largest amplitude received after the surface reflection wave is taken as the back reflection wave. However, depending on the thickness of the object being measured, sometimes the amplitude of the received wave that is not a back reflection wave is greater than the amplitude of the back reflection wave. Therefore, in the prior art, it is possible to mistakenly detect a received wave that is not a back reflection wave as a back reflection wave. Thus, the prior art suffers from low thickness measurement accuracy.

[0008] In view of this problem, the purpose of this disclosure is to provide a thickness measuring device and a thickness measuring method that can measure the thickness of the object to be measured with high precision.

[0009] Methods for solving problems

[0010] To address the aforementioned issues, one aspect of the thickness measuring apparatus disclosed herein includes: an ultrasonic transmitter capable of transmitting ultrasonic waves to an object to be measured; an ultrasonic receiver capable of receiving ultrasonic waves reflected by the object to be measured; a first extraction unit capable of extracting a first reflected wave reflected on a first surface of the object to be measured from the ultrasonic waves received by the ultrasonic receiver (i.e., the received wave); a second extraction unit capable of extracting multiple candidates for second reflected waves reflected on a second surface of the object to be measured located on the back side of the first surface from the received wave; a consistency calculation unit capable of calculating the consistency between the first reflected wave and the candidate for each of the multiple candidates; a candidate determination unit capable of determining the candidate with the highest consistency from the multiple candidates as the second reflected wave; and a thickness calculation unit capable of calculating the thickness of the object to be measured based on the reception time of the first reflected wave in the ultrasonic receiver and the reception time of the second reflected wave determined by the candidate determination unit.

[0011] Additionally, a range determination unit may be provided, which determines the range of the receiving period estimated to include the second reflected wave based on the estimated thickness range of the object being measured, and a second extraction unit extracts multiple candidates from the received wave within the range.

[0012] Alternatively, the consistency calculation unit can compare the period during which the ultrasonic receiver is receiving the first reflected wave with the period during which the candidate is receiving the second reflected wave, and set the consistency of the candidate that is closer to the period during which the first reflected wave is being received to be greater.

[0013] To address the aforementioned issues, one aspect of the thickness measurement method disclosed herein includes: a step of transmitting an ultrasonic wave to the object to be measured; a step of receiving the ultrasonic wave reflected by the object to be measured; a step of extracting a first reflected wave reflected on a first surface of the object to be measured from the received ultrasonic wave, i.e., the received wave; a step of extracting multiple candidates for second reflected waves reflected on a second surface of the object to be measured located on the back side of the first surface from the received wave; a step of calculating the consistency between the first reflected wave and the candidate for each candidate; a step of determining the candidate with the highest consistency as the second reflected wave from the multiple candidates; and a step of calculating the thickness of the object to be measured based on the reception time of the first reflected wave and the determined reception time of the second reflected wave.

[0014] Invention Effects

[0015] According to this disclosure, the thickness of the object being measured can be determined with high precision. Attached Figure Description

[0016] Figure 1 The thickness measuring device described in the embodiment is explained.

[0017] Figure 2 This illustrates an example of receiving a wave.

[0018] Figure 3A This describes multiple ultrasound waves.

[0019] Figure 3B Indicates parallel reception Figure 3A The waveform of the received wave during ultrasound is shown.

[0020] Figure 4A yes Figure 2 An enlarged view of the gate area.

[0021] Figure 4B yes Figure 2 A magnified view of the surface reflected waves.

[0022] Figure 5 This is a flowchart illustrating the processing flow of the thickness measurement method according to the implementation method.

[0023] Figure 6A This describes the received wave within the gate's range.

[0024] Figure 6B This describes surface-reflected waves. Detailed Implementation

[0025] The embodiments of this disclosure will now be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific values ​​shown in these embodiments are merely illustrative for ease of understanding and do not limit the scope of this disclosure unless specifically stated otherwise. Furthermore, in this specification and the accompanying drawings, elements having substantially the same function or structure are labeled with the same reference numerals, and repeated descriptions are omitted. Additionally, elements not directly related to this disclosure are omitted from the illustrations.

[0026] Figure 1 This embodiment describes the thickness measuring device 100. Figure 1 In the diagram, a dashed arrow indicates the transmitted ultrasonic wave. Figure 1 In the image, the solid arrow represents a surface-reflected wave. Figure 1 In the image, the dashed arrow represents the back-reflected wave.

[0027] The thickness measuring device 100 uses ultrasound to measure the thickness D of the object to be measured, S, from the surface H (first surface). Because the back surface R (second surface) of the object to be measured is covered, the thickness D cannot be directly measured. Furthermore, the back surface R is the surface of the object to be measured S located on the back side of surface H.

[0028] like Figure 1As shown, the thickness measuring device 100 measures the thickness D of the object S based on the difference between the reception time of the surface reflected wave (first reflected wave) and the reception time of the back reflected wave (second reflected wave). The surface reflected wave and the back reflected wave are obtained by sending ultrasonic waves to the surface H of the object S. The surface reflected wave is an ultrasonic wave that is reflected from the surface H of the object S. The back reflected wave is an ultrasonic wave that propagates within the object S and is reflected from the back surface R.

[0029] In this embodiment, the thickness measuring device 100 checks the object S, which is a standard with approximately equal thickness D.

[0030] In this embodiment, the thickness measuring device 100 includes an ultrasonic transmitter 110, an ultrasonic receiver 120, a central control unit 130, and a memory 140.

[0031] The ultrasonic transmitter 110 is configured to transmit ultrasonic waves to the object S being measured. The ultrasonic receiver 120 is configured to receive ultrasonic waves reflected by the object S being measured. In this embodiment, the ultrasonic receiver 120 receives at least surface-reflected waves and back-reflected waves.

[0032] The central control unit 130 is composed of a semiconductor integrated circuit containing a CPU (central processing unit). The central control unit 130 reads programs and parameters from ROM to operate the CPU. The central control unit 130 works in conjunction with RAM or other circuits that serve as the working area to manage and control the entire thickness measuring device 100.

[0033] The memory 140 is composed of ROM, RAM, flash memory, HDD, etc. The memory 140 stores programs and various data for the central control unit 130. In this embodiment, the memory 140 stores the estimated thickness of the object S to be measured, the tolerance of the object S to be measured, the sound velocity of the object S to be measured, and the threshold value described later. The estimated thickness of the object S to be measured is obtained through prior actual measurement, such as cutting the object S.

[0034] In this embodiment, the central control unit 130 functions as the ultrasonic control unit 210, the range determination unit 212, the first extraction unit 214, the second extraction unit 216, the consistency calculation unit 218, the candidate determination unit 220, the thickness calculation unit 222, and the pass / fail determination unit 224.

[0035] The ultrasonic control unit 210 causes the ultrasonic transmitter 110 to transmit ultrasonic waves. Additionally, the ultrasonic control unit 210 converts the ultrasonic waves received by the ultrasonic receiver 120 into electrical signals (voltage values).

[0036] The range determination unit 212 determines the range estimated to include the reception period (reception time) of the back-reflected wave based on the estimated thickness range stored in the memory 140. Hereinafter, the range estimated to include the reception period of the back-reflected wave will be referred to as the gate range. The determination of the gate range by the range determination unit 212 will be described in detail later.

[0037] The first extraction unit 214 extracts the surface reflection wave reflected from the surface H of the object to be measured S from the ultrasonic wave received by the ultrasonic receiver 120, i.e., the received wave.

[0038] Figure 2 This illustrates an example of received waves. Figure 2 In the diagram, the vertical axis represents the displacement (voltage [V]). Additionally, in... Figure 2 In the diagram, the horizontal axis represents the reception time [μsec].

[0039] like Figure 2 As shown, the first extraction unit 214 extracts the received wave that exceeds a predetermined displacement amount (absolute value) and is the earliest received wave by the ultrasonic receiver 120, and uses it as a surface reflection wave.

[0040] In addition, such as Figure 2 As shown, in this embodiment, the displacement of the surface reflected wave starts from a reference value (e.g., 0V), shifts positively (+) to reach its maximum value, then shifts negatively (-) to reach its minimum value (less than the reference value), and finally shifts positively again to return to the reference value. Similarly, the displacement of the back reflected wave starts from a reference value, shifts negatively to reach its minimum value, then shifts positively to reach its maximum value (exceeding the reference value), and finally shifts negatively again to return to the reference value. That is, in this embodiment, the phases of the surface reflected wave and the back reflected wave are reversed.

[0041] Furthermore, there are cases where the displacement of the surface-reflected wave starts from the reference value, shifts negatively to a minimum, then shifts positively to a maximum exceeding the reference value, and finally shifts negatively back to the reference value. Similarly, there are cases where the displacement of the back-reflected wave starts from the reference value, shifts positively to a maximum, then shifts negatively to a minimum less than the reference value, and finally shifts positively back to the reference value. Therefore, there are cases where the displacement pattern of the surface-reflected wave is equal in phase with that of the back-reflected wave, and there are also cases where the phases are reversed.

[0042] The back-reflected wave arrives at the ultrasonic receiver 120 after the surface-reflected wave. Therefore, conventionally, the received wave with the largest amplitude (displacement) received after the surface-reflected wave is designated as the back-reflected wave. However, for example, when the thickness D of the object S being measured is small, sometimes the amplitude of the received wave that is not the back-reflected wave is greater than the amplitude of the back-reflected wave.

[0043] Figure 3A This describes multiple ultrasound waves. Figure 3B Indicates parallel reception Figure 3A The waveform of the received wave during ultrasound is shown. Figure 3A In the diagram, the solid line represents the first wave, and the dashed line represents the second wave.

[0044] like Figure 3A As shown, the first and second waves arrive at the ultrasonic receiver 120 in parallel. Therefore, as... Figure 3B As shown, a portion of the first wave and a portion of the second wave are combined, and the amplitude of the combined wave is greater than that of the first wave or the second wave.

[0045] When the thickness D of the object S being measured is small (thin), the propagation time of the ultrasonic waves within the object S is short. Therefore, a portion of the surface-reflected wave (the rear end of the received wave) and a portion of the back-reflected wave (the front end of the received wave) arrive at the ultrasonic receiver 120 simultaneously. Consequently, they are combined, and sometimes the ultrasonic receiver 120 detects a received wave with an amplitude larger than that of the back-reflected wave. Additionally, there are cases where the noise amplitude is larger than that of the back-reflected wave. Therefore, in the prior art, it is possible to misdetect a received wave that is not a back-reflected wave as a back-reflected wave. Thus, in the prior art, there is a problem of reduced accuracy in the measurement of thickness D.

[0046] Therefore, the thickness measuring device 100 includes a second extraction unit 216, a consistency calculation unit 218, and a candidate determination unit 220, thereby improving the detection accuracy of back reflection waves.

[0047] The second extraction unit 216 extracts multiple candidate back-reflected waves that are reflected from the back side R of the object being measured S from the received waves received by the ultrasonic receiver 120. In this embodiment, the second extraction unit 216 extracts multiple candidate waves from the received waves within the gate range.

[0048] return Figure 2 To explain, the range determination unit 212 calculates the estimated arrival time (hereinafter referred to as the "estimated arrival time") Td of the back-side reflected wave, based on the estimated thickness stored in the memory 140 and taking the surface reflected wave as the starting point. Furthermore, the range determination unit 212 determines the gate range as a predetermined period (e.g., approximately several hundred nanoseconds) before and after the estimated arrival time Td. Additionally, the predetermined time is determined based on the tolerance stored in the memory 140.

[0049] Then, the second extraction unit 216 extracts the received wave within the determined gate range as a candidate for the back-reflected wave.

[0050] Figure 4A yes Figure 2An enlarged view of the gate area. Figure 4B yes Figure 2 A magnified view of the surface reflected waves. (See image below.) Figure 4A As shown, in this embodiment, the second extraction unit 216 extracts the received wave whose starting point is a reference value (e.g., 0V) as a candidate for the back reflection wave. Therefore, the second extraction unit 216 extracts candidates A and B as candidates for the back reflection wave, and does not extract the received wave X which has no starting point.

[0051] The consistency calculation unit 218 calculates the consistency between the surface reflected wave and the candidate for each of the multiple candidates A and candidate B. In this embodiment, the consistency calculation unit 218 compares the period during which the surface reflected wave is being received with the period during which candidates A and B are being received, and sets the consistency of the candidate that is closer to the period during which the surface reflected wave is being received to be greater.

[0052] like Figure 4B As shown, the consistency calculation unit 218 calculates the period (time) from the reception time THs at the start of the surface reflected wave to the reception time THe at the end of the surface reflected wave. Additionally, as... Figure 4A As shown, the consistency calculation unit 218 calculates the period from the reception time Tas of the starting point of candidate A to the reception time Tae of the ending point of candidate A. Similarly, the consistency calculation unit 218 calculates the period from the reception time Tbs of the starting point of candidate B to the reception time Tbe of the ending point of candidate B.

[0053] Then, the consistency calculation unit 218 calculates the consistency between the period of receiving the surface reflected wave (the period from time Ths to time The) and the period of receiving candidate A (the period from time Tas to time Tae), and the consistency between the period of receiving the surface reflected wave and the period of receiving candidate B (the period from time Tbs to time Tbe).

[0054] The candidate determination unit 220 determines the candidate with the highest consistency as the back reflection wave from a plurality of candidates A and candidates B. In this embodiment, the consistency calculation unit 218 determines candidate B as the back reflection wave, wherein candidate B has a period close to the period of receiving surface reflection waves.

[0055] The thickness calculation unit 222 calculates the thickness D of the object to be measured S based on the reception time of the surface reflection wave in the ultrasonic receiver 120 and the reception time of the back reflection wave (candidate B) determined by the candidate determination unit 220.

[0056] D = (TH - TR) × C / 2 ... Equation (1)

[0057] In equation (1) above, TH is the receiving time of the surface reflected wave. TR is the receiving time of the back-reflected wave. C is the sound velocity of the object S being measured.

[0058] In this embodiment, the receiving time TH of the surface reflected wave is the moment when the displacement in the surface reflected wave initially reaches an extreme value (inflection point). Similarly, the receiving time TR of the back reflected wave is the moment when the displacement in the back reflected wave initially reaches an extreme value.

[0059] As described above, the displacement of the surface reflected wave, after reaching its maximum value by moving positively from the reference value, shifts negatively to become its minimum value, which is less than the reference value, and then shifts positively again to return to the reference value. Similarly, the displacement of the back-side reflected wave, after reaching its minimum value by moving negatively from the reference value, shifts positively to become its maximum value, which exceeds the reference value, and then shifts negatively again to return to the reference value.

[0060] Therefore, the receiving time TH of the surface-reflected wave is the moment when the displacement reaches its maximum value. Conversely, the receiving time TR of the back-reflected wave is the moment when the displacement reaches its minimum value.

[0061] The pass / fail determination unit 224 determines whether the calculated thickness D of the test object S is above a predetermined threshold. The threshold is the minimum required thickness of the test object S. If the pass / fail determination unit 224 determines that the thickness D of the test object S is above the threshold, it determines that the test object S is a qualified product. On the other hand, if the pass / fail determination unit 224 determines that the thickness D of the test object S is below the threshold, it determines that the test object S is a non-qualified product.

[0062] [Thickness Measurement Method]

[0063] Next, the thickness measurement method for measuring the thickness D of the object S using the aforementioned thickness measuring device 100 will be described. Figure 5 This is a flowchart illustrating the processing flow of the thickness measurement method in this embodiment. For example... Figure 5 As shown, the thickness measurement method of this embodiment includes a sending process S110, a receiving process S120, a surface reflection wave extraction process S130, a candidate extraction process S140, a consistency calculation process S150, a back reflection wave determination process S160, a thickness calculation process S170, a pass / fail determination process S180, a pass / fail determination process S190, and a fail / fail determination process S200. Each process will be described below.

[0064] [Sending process S110]

[0065] The transmitting process S110 is the process by which the ultrasonic transmitter 110 transmits ultrasonic waves to the object to be measured S based on the control command of the ultrasonic control unit 210.

[0066] [Receiving process S120]

[0067] The receiving process S120 is the process by which the ultrasonic receiver 120 receives the ultrasonic waves reflected by the object being measured S.

[0068] [Surface Reflection Wave Extraction Process S130]

[0069] The surface reflection wave extraction process S130 is the process by which the first extraction unit 214 extracts the surface reflection wave reflected from the surface H of the object to be measured S from the ultrasonic wave received in the receiving process S120, i.e., the received wave.

[0070] [Supplementary Extraction Process S140]

[0071] The candidate extraction step S140 is a step in which the second extraction unit 216 extracts multiple candidate back-reflected waves that have been reflected from the back side R of the object to be measured S from the received wave received in the receiving step S120. In this embodiment, the second extraction unit 216 extracts candidate back-reflected waves from a gate range determined by the range determination unit 212.

[0072] [Consistency Calculation Process S150]

[0073] The consistency calculation process S150 is a process in which the consistency calculation unit 218 calculates the consistency between the surface reflected waves extracted in the surface reflected wave extraction process S130 and the candidates extracted in the candidate extraction process S140 for multiple candidates.

[0074] [Backside Reflection Wave Determination Process S160]

[0075] The back reflection wave determination process S160 is the process by which the candidate determination unit 220 determines the candidate with the highest consistency from among the multiple candidates extracted in the candidate extraction process S140 as the back reflection wave.

[0076] [Thickness calculation process S170]

[0077] The thickness calculation process S170 is a process in which the thickness calculation unit 222 calculates the thickness D of the object S based on the reception time TH of the surface reflected wave extracted in the surface reflected wave extraction process S130 and the reception time TR of the back reflected wave determined in the back reflected wave determination process S160.

[0078] [Pass / Fail Judgment Process S180]

[0079] The pass / fail determination process S180 is a process in which the pass / fail determination unit 224 determines whether the object to be measured S is pass or fail based on the thickness D of the object to be measured calculated in the thickness calculation process S170. In this embodiment, the pass / fail determination unit 224 determines whether the thickness D of the object to be measured S calculated in the thickness calculation process S170 is above or below a threshold. As a result, if the pass / fail determination unit 224 determines that the thickness D of the object to be measured S is above or below the threshold (yes in S180), the process is transferred to the pass determination process S190. On the other hand, if the pass / fail determination unit 224 determines that the thickness D of the object to be measured S is not above or below the threshold, that is, less than the threshold (no in S180), the process is transferred to the fail determination process S200.

[0080] [Pass / Fail Judgment Process S190]

[0081] The conformity determination process S190 is the process by which the conformity determination unit 224 determines the measured object S as a conforming product.

[0082] [Non-conforming inspection process S200]

[0083] The non-conformance judgment process S200 is the process by which the conformity judgment department 224 determines the measured object S as a non-conforming product.

[0084] As explained above, the thickness measuring apparatus 100 of this embodiment and the thickness measuring method using the thickness measuring apparatus extract multiple candidates for back-side reflection waves and calculate the consistency between the multiple candidates and the surface reflection waves. Then, the thickness measuring apparatus 100 uses the candidate with the highest consistency as the back-side reflection wave to calculate the thickness D of the object S to be measured.

[0085] In existing technologies that detect received waves with the largest amplitude (displacement) as back reflection waves, even received waves with low consistency with surface reflection waves can be misdetected as back reflection waves if their amplitude is the largest. In contrast, the thickness measuring device 100 includes a consistency calculation unit 218 and a candidate determination unit 220, thus enabling it to extract candidates with high consistency with surface reflection waves as back reflection waves regardless of amplitude. Therefore, the thickness measuring device 100 can reduce the probability of misdetecting received waves that are not back reflection waves as back reflection waves. Therefore, the thickness measuring device 100 can detect back reflection waves with high accuracy. Therefore, the thickness measuring device 100 can measure the thickness D of the object S with high accuracy.

[0086] Furthermore, as described above, the thickness measuring device 100 includes a range determination unit 212. This allows the thickness measuring device 100 to further suppress false detections of back-reflected waves. Additionally, compared to extracting back-reflected wave candidates from all received waves, the thickness measuring device 100 can reduce the number of candidates. Therefore, the thickness measuring device 100 can reduce the processing load on the second extraction unit 216.

[0087] Furthermore, as described above, the consistency calculation unit 218 compares the period during which the surface reflection wave is being received with the periods during which candidate A and candidate B are being received, and identifies the candidate whose period is closer to the period during which the surface reflection wave is being received as the candidate with higher consistency. As a result, the thickness measuring device 100 can detect the back reflection wave with high accuracy.

[0088] The embodiments have been described above with reference to the accompanying drawings, but it is self-evident that this disclosure is not limited to the above embodiments. Those skilled in the art can conceive of various modifications or alterations within the scope of the protection described, and these naturally also fall within the technical scope of this disclosure.

[0089] For example, in the above embodiment, the consistency calculation unit 218 calculates the consistency between the period during which the surface reflected wave is being received and the period during which the candidate wave is being received. However, the consistency calculation unit 218 may also calculate the consistency between the surface reflected wave and the candidate wave using other methods.

[0090] Figure 6A This describes the received wave within the gate's range. Figure 6B This describes surface-reflected waves.

[0091] In the variant example, such as Figure 6A As shown, the second extraction unit 216 extracts extreme values ​​within the gate range as candidates. However, in a modified example, similar to the embodiment described above, the second extraction unit 216 does not extract received waves whose starting point is not a reference value as candidates for back-reflected waves. That is, in the modified example, the second extraction unit 216 does not extract extreme values ​​1 and 2 whose displacement between them and the immediately preceding extreme value is not a reference value as candidates. Therefore, the second extraction unit 216 extracts candidates ua, ub, and uc with positive (+) extreme values ​​and candidates ba, bb, and bc with negative (-) extreme values.

[0092] Then, the consistency calculation unit 218 calculates the virtual connection nu(Hmax) between the extreme value Hmax of the surface reflected wave and the reference value k1 immediately preceding the extreme value Hmax. Figure 6B The degree of agreement between the absolute value of the slope of the line (represented by a single-dotted line) and the absolute value of the slope of the following virtual connection, where the virtual connection is the virtual connection between candidate ba, candidate bb, candidate bc and the immediate reference value. For example, as Figure 6BAs shown, the consistency calculation unit 218 calculates the virtual wiring mb between the candidate bb and the reference value k4 immediately preceding the candidate bb (in Figure 6A The degree of consistency between the absolute value of the slope of the line (represented by a single-dot dash) and the absolute value of the slope of the virtual line nu of the surface reflected wave.

[0093] In addition, the consistency calculation unit 218 calculates the virtual connection nb between the extreme value Hmin of the surface reflected wave and the reference value k2 immediately preceding the extreme value Hmin. Figure 6B The degree of agreement between the absolute value of the slope of the line (represented by a single-dotted line) and the absolute value of the slope of the following virtual connection, where the virtual connection is the virtual connection between the candidate ua, candidate ub, candidate uc and the immediate reference value. For example, as Figure 6B As shown, the consistency calculation unit 218 calculates the virtual connection mu (in the candidate ua and the reference value k3 immediately preceding the candidate ua) between the candidate ua and the reference value k3. Figure 6A The degree of consistency between the absolute value of the slope of the dotted line (represented by a dashed line) and the absolute value of the slope of the virtual line nb of the surface reflected wave.

[0094] Then, the consistency calculation unit 218 determines the candidate with the highest consistency between the absolute value of the slope of the virtual connection nu and the absolute value of the slope of the virtual connection nb as the back reflection wave. Therefore, the back reflection wave can also be detected with high accuracy in the consistency calculation unit 218 of the modified example.

[0095] Furthermore, in the modified example, the consistency calculation unit 218 calculates the slope of the virtual connection between the extreme value and the immediately preceding reference value. If the consistency calculation unit 218 calculates the slope of the virtual connection between the extreme value and the immediately preceding reference value, when the candidate's endpoint overlaps with the immediately preceding received wave, the candidate's endpoint may not become the reference value. Therefore, the second extraction unit 216 may fail to extract the extreme value of the back-reflected wave as a candidate. In contrast, the modified example's consistency calculation unit 218, by calculating the slope of the virtual connection with the immediately preceding reference value, can reduce the probability that the extreme value of the back-reflected wave is not extracted as a candidate.

[0096] In addition, unlike the above-described embodiments and variations, the consistency calculation unit 218 can also calculate the consistency between the reception periods of the extreme values ​​of the surface reflected wave (the period from the extreme value Hmax to the extreme value Hmin) and the reception periods of the candidate extreme values ​​(the period from the minimum value to the maximum value).

[0097] Furthermore, in the above embodiment, the thickness measuring device 100 is described as having a range determination unit 212. However, the range determination unit 212 is not a necessary component.

[0098] Furthermore, in the above embodiment, an example is given of the case where the pass / fail determination unit 224 determines whether the thickness D of the object to be measured, calculated by the thickness calculation unit 222, is above a threshold. However, the pass / fail determination unit 224 may also determine whether the thickness D of the object to be measured, calculated by the thickness calculation unit 222, is within a predetermined threshold range. In this case, the pass / fail determination unit 224 determines that the object is passable if the thickness D is within the threshold range, and fails if the thickness D is outside the threshold range.

[0099] Furthermore, in the above embodiment, an example is given where the first extraction unit 214 extracts the surface reflected wave as the first reflected wave, and the second extraction unit 216 extracts multiple candidates for back-reflected waves as candidates for the second reflected wave. However, the first extraction unit 214 may also extract the back-reflected wave as the first reflected wave, and the second extraction unit 216 may extract multiple candidates for surface reflected waves as candidates for the second reflected wave. In this case, the consistency calculation unit 218 calculates the consistency between the back-reflected wave and the surface reflected wave candidates for each of the multiple candidates.

[0100] Explanation of reference numerals in the attached figures

[0101] 100: Thickness measuring device

[0102] 110: Ultrasonic transmitter

[0103] 120: Ultrasonic receiver

[0104] 212: Scope Determination Department

[0105] 214: First Extraction Section

[0106] 216: Second Extraction Section

[0107] 218: Consistency Calculation Department

[0108] 220: Alternate Decision-Making Department

[0109] 222: Thickness Calculation Section.

Claims

1. A thickness measuring device, characterized in that, have: An ultrasonic transmitter that sends ultrasonic waves toward the object being measured. An ultrasonic receiver capable of receiving ultrasonic waves reflected by the object being measured; The first extraction unit extracts the first reflected wave that was reflected from the first surface of the object being measured from the ultrasonic wave received by the ultrasonic receiver, i.e., the received wave. The second extraction unit extracts from the received wave a plurality of candidates for second reflected waves that were reflected from the second surface of the object being measured, located on the back side of the first surface; The consistency calculation unit calculates the consistency between the first reflected wave and the candidate for each of the candidates; The candidate decision unit determines the candidate with the highest consistency from among the multiple candidates as the second reflected wave; as well as The thickness calculation unit calculates the thickness of the object to be measured based on the reception time of the first reflected wave in the ultrasonic receiver and the reception time of the second reflected wave determined by the candidate determination unit. The thickness measuring device includes a range determining unit that determines a range estimated to include the reception period of the second reflected wave based on an estimated thickness range of the object being measured. The second extraction unit extracts a plurality of the candidates from the received waves within the range.

2. The thickness measuring device according to claim 1, characterized in that, The consistency calculation unit compares the period during which the ultrasonic receiver is receiving the first reflected wave with the period during which a candidate is receiving the second reflected wave, and sets the consistency of the candidate closer to the period during which the first reflected wave is being received to be greater.

3. A thickness measurement method, characterized in that, Include: The process of sending ultrasonic waves to the object being measured; A process of receiving ultrasonic waves reflected by the object being measured; The process of extracting the first reflected wave that has been reflected from the first surface of the object being measured from the received ultrasonic wave, i.e., the received wave; The process of extracting multiple candidate second reflected waves that were reflected from the second surface of the object being measured, located on the back side of the first surface, from the received wave; The process of calculating the consistency between the first reflected wave and the candidate wave for each of the multiple candidates; The process of determining the candidate with the highest consistency from among multiple candidates as the second reflected wave; as well as The process of calculating the thickness of the object to be measured based on the reception time of the first reflected wave and the determined reception time of the second reflected wave. The thickness measurement method includes a step of determining, based on an estimated thickness range of the object being measured, a range estimated to include the reception period of the second reflected wave. Multiple candidates are extracted from the received waves within the range.

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