GB2525755A

GB2525755A - Ultrasonic wave transmitter and underwater detection apparatus

Info

Publication number: GB2525755A
Application number: GB1506024.7A
Authority: GB
Inventors: Norimasa Michiue; Akira Okunishi
Original assignee: Furuno Electric Co Ltd
Current assignee: Furuno Electric Co Ltd
Priority date: 2014-04-10
Filing date: 2015-04-09
Publication date: 2015-11-04
Anticipated expiration: 2035-04-09
Also published as: JP6317614B2; GB2525755B; GB201506024D0; JP2015203566A

Abstract

The ultrasonic wave transmitter 10 generates a drive signal to operate an ultrasonic oscillator 2a and causing the ultrasonic oscillator to transmit an ultrasonic wave having a desired amplitude value. The transmitter includes a counter 11 configured to increment from an initial value by a predetermined step value at a sampling cycle and output a first counter value (see fig 4), or decrement from an initial value by a predetermined step value at a sampling cycle and output a second counter value (see fig 19), a first drive signal generator 20 configured to compare the either one of the fast and second counter values with a threshold (Thr) and generate a first drive signal, and a transducer (2) configured to transmit the ultrasonic wave from the ultrasonic oscillator (2a) operated based on the first drive signal. A number of alternate embodiments are discussed (figs 10-19) including the use of two threshold values.

Description

ULTRASONIC WAVE TRANSMITTER AND UNDERWATER DETECTION

APPARATUS

Technical Field

[0001] This disclosure relates to an ultrasonic wave transmitter, which has a drive signal generator configured to generate a drive signal for generating an ultrasonic waveform, and also relates to an underwater detection apparatus, which includes the ultrasonic wave transmitter.

Background of the Invention

[0002] Conventionally, it has been known to control an envelope of an ultrasonic wave by controlling a pulse width of a pulse-shaped drive signal (i.e., by a PWM control). For example, according to JP41 16930B. a PWM control is performed on a digital control signal (drive signal) and a transmission signal for generating an ultrasonic wave by oscillating an oscillator is generated based on the digital control signal. As described in paragraph [0054] and Fig. 4 of JP4116930B, the drive signal is designed based on a comparison between a RAMP signal formed into a saw tooth shape and an analog control signal (transmission signal).

[0003] In generating a digital drive signal, the following method may also be considered.

Fig. 20 is a block diagram illustrating a configuration of a drive signal generator 100 in one example. Fig. 21 shows charts for describing a shape of a waveform of the drive signal generated by the drive signal generator 100. In this example of Figs. 20 and 21, a counter 101 adds a predetermined step value to for example an initial value at a sampling cycle and outputs a counter value to the drive signal generator 100. When the counter value becomes higher than a predetermined value, the counter value corresponds to the amount exceeding the predetermined value.

[0004] The drive signal generator 100 includes two comparators 102a and 102b, and a logical conjunction calculator 103.

[0005] Each of the comparators 1 02a and I 0Th compares the courner value inpuned from the counter 101 with a threshoM, and a comparison result thereof is outpuaed to the thgical conjunction calculator 103. Specifically, one of the comparators (the comparator 102a) compares a threshold Thr_A with the counter value. When the counter value is lower than the threshold Thr_A, the comparator 102a outputs an OFF signal expressed by "0" in the binary code, and when the counter value is the threshold Thr_A or higher, the comparator 102a outputs an ON signal expressed by "1" in the binary code. Moreover, the other comparator 102b compares a threshold Thr_B (>Thr_A) with the counter value. When the counter value is higher than the threshold Thr_B, the comparator 102b outputs an OFF sign& expressed by 0 in the binary code, and when the counter value is the threshoki Thr_B or thwer, the comparator 1 02h outputs an ON signa' expressed by I in the binary code.

[0006] The logical conjunction calculator 103 calculates a thgical conjunction of the comparison results outputted from the comparators 102a and 102b. The operation result obtained by the logical conjunction calculator 33 becomes 1 when the comparison results from the comparators 102a and 102h are both 1, which is, to describe it with reference to Fig. 21, a case where the counter value is between the threshold Thr_A and the threshold Thr_B. Thus, as illustrated in Fig. 21, when the counter value becomes a value between the thresholds Thr_A and Thr_B. the drive signal outputted from the logical conjunction calculator 103 becomes an ON state until the counter value is higher than the threshold Thr_B, and in other cases, the drive signa' outputted from the logica' coniunction calculator 103 becomes an OFF state.

[0007] Meanwhile, a pulse width of the drive signal generated by the drive signal generator 100 described above may yary due to the numeric values of the counter values being discrete, as illustrated in Fig. 21. in this case, as illustrated in Fig. 22, an amplitude of an envelope of a waveform of the ultrasonic wave is pulsed, and the envelope may become unsutble.

Summary of the Invention

[00081 This disclosure is made in view of the above situations and aims to stabilize an envelope of an ultrasonic waveform.

[00091 According to one aspect of this disclosure, an ultrasonic wave transmitter is provided. The ultrasonic wave transmitter generates a drive signal to operate an ultrasonic oscillator and causing the ultrasonic oscillator to transmit an ultrasonic wave having a desired amplitude value. The ultrasonic wave transmitter includes a counter configured to increment from an initial value by a predetermined step value at a sampling cycle and output a first counter value. or decrement from an initial value by a predetermined step value at a sampling cycle and output a second counter value, a first drive signal generator configured to compare the either one of the first and second counter values outputted from the counter with a threshold and generate a first drive signal that becomes an ON state when the first counter value is higher than the threshold or the second counter value is lower than the threshold, and then becomes an OFF state after a predetermined time period since the first drive signal becomes the ON state, and a transducer configured to transmit the ultrasonic wave from the ultrasonic oscillator operated based on the first drive signal.

When the first counter value becomes higher than a first predetermined value, the first counter value becomes a value determined based on the amount exceeding the first predetermined value and is incremented again by the predetermined step value, and when the second counter value becomes lower than a second predetermined value, the second counter value becomes a value determined based on the amount falling below the second predetermined value and is decremented again by the predetermined step value.

[00101 The ultrasonic wave transmitter preferably also includes a pulse width controller configured to control a pulse width of the first drive signal by controlling the predetermined time period.

[00111 The ultrasonic wave transmitter preferably also includes a threshold controller configured to control the threshold according to the pulse width controlled by the pulse width controller.

[0012] The pulse width controller preferably performs a control of extending the predetermined time period, every time an envelope of the ultrasonic wave rises. The threshold controller preferably performs a control of reducing the threshold every time the envelope of the ultrasonic wave rises in the case where the counter outputs the first counter value, or the threshold controller preferably performs a control of increasing the threshold every time the envelope of the ultrasonic wave rises in the case where the counter outputs the second counter value.

[0013] The pulse width controller preferably performs a control of shortening the predetermined time period every time the envelope of the ultrasonic wave falls. The threshold controller preferably performs a control of increasing the threshold every time the envelope of the ultrasonic wave falls in the case where the counter outputs the first counter value, or the threshold controller preferably performs a control of reducing the threshold every time the envelope of the ultrasonic wave falls in the case where the counter outputs the second counter value.

[0014] The first drive signal generator preferably includes at least two first drive signal generators. The threshold preferably includes a first threshold and a second threshold higher than the first threshold. One or more of the first drive signal generators preferably compare the either one of the first and second counter values with the first threshold. The rest of the first drive signal generators preferably compare the either one of the first and second counter values with the second threshold. The ultrasonic oscillator is preferably operated by the first drive signal generated by the one or more of the first drive signal generators and the first drive signal generated by the rest of the first drive signal generators.

[0015] The ultrasonic wave transmitter preferably also includes a second drive signal generator configured to compare the either one of the first and second counter values outputted from the counter with a lower limit threshold and an upper limit threshold, and generate a second drive signal that becomes an ON state when the either one of the first and second counter values is between the lower limit threshold and the upper limit threshold, and becomes an OFF state when the either one of the first and second counter values is lower than the tower limit thresh&d or higher than the upper Hmit threshold. When the amphtude value of the ifitrasonic wave is tower than a predetermined value, the transducer preferably transmits the ultrasonic wave from the ultrasonic oscillator operated based on the first drive signal. When the amplitude value of the ultrasonic wave is the predetermined value or higher, the transducer preferably transmits the ultrasonic wave from the ultrasonic oscillator operated based on the second drive signal.

[0016] The ultrasonic wave transmitter preferably also includes a second drive signal generator configured to compare the either one of the first and second counter values outputted from the counter with a lower limit threshold and an upper limit threshold, and generate a second drive signal that becomes an ON state when the either one of the first and second counter values is between the tower limit threshold and the upper Bmit threshoM, and becomes an OFF state when the either one of the first and second counter values is lower than the lower limit threshold or higher than the upper limit threshold. When the envelope of the ultrasonic wave rises or falls, the transducer preferably transmits the ifitrasonic wave from the ulirasonic osciflator operated based on the second drive signaL In a part of the envelope of the ultrasonic wave after rising and before falling, the transducer preferably transmits the ultrasonic wave from the ultrasonic oscillator operated based on the first drive signal.

[0017] The first drive signal generator preferably includes a comparator configured to compare the either one of the first and second counter values outputted from the counter with the threshoki, and output a comparison result thereof, a register configured to receive the comparison result from the comparator, store the comparison result, and when the next comparison result is inputted therein from the comparator, output the comparison result stored until the next comparison result is inputted, and a logical disjunction calculator configured to calculate a logical disjunction of the comparison result outputted from the comparator and a value obtained by inverting the comparison result outputted from the register.

[0018] According to another aspect of this disclosure, an underwater detection apparatus is provided. The underwater detection apparatus includes the ultrasonic wave transmitter having any one of the above configurations, and detects a target object underwater based on an echo signal of the ultrasonic wave transmitted from the ultrasonic wave transmittet Effect(s) of the Invention [00191 According to this disclosure, the envelope of the ultrasonic waveform can be stabilized.

Brief Description of the Drawing(s)

[00201 The present disclosure is illustrated by way of example and not by way of limitation in the figures of the accompanying drawings, in which the like reference numerals indicate like elements and in which: [0020.1] Fig. 1 is a block diagram illustrating a configuration of an underwater detection apparatus according to an embodiment of this disclosure; [0020.2] Fig. 2 is a block diagram illustrating a configuration of an ultrasonic wave transmitter in Fig. 1; [0020.3] Fig. 3A is a view illustrating one example of an ultrasonic waveform transmitted from an ultrasonic oscillator, and Fig. 3B is a view illustrating one example of a drive signal that causes a transmission signal for generating the ultrasonic waveform; [0020.4] Fig. 4 shows charts illustrating a relationship of a counter value outputted from a cycle variable counter as needed, with the drive signal generated based on the counter value; [0020.5] Fig. 5 shows a chart of the counter value in Part (A) thereof, a chart of the drive signal in Part (B) thereof, a view of a transmission waveform in Part (C) thereof, and a view of a basic waveform in Part (D) thereof, in a case where a threshold gradually becomes low when an envelope rises; [0020.6] Fig. 6 shows a chart of the counter value in Part (A) thereof, a chart of the drive signal in Part (B) thereof, a view of the transmission waveform in Part (C) thereof, and a view of the basic waveform in Part (D) thereof, in a case where the threshold is fixed when the envelope rises; [0020.7] Fig. 7 shows a chart of the counter value in Part (A) thereof, a chart of the drive signal in Part (B) thereof, a view of the transmission waveform in Part (C) thereof, and a view of the basic waveform in Part (D) thereof, in a case where the threshold gradually becomes high when the envelope falls; [0020.8] Fig. 8 shows a chart of the counter value in Part (A) thereof, a chart of the drive signal in Part (B) thereof, a view of the transmission waveform in Part (C) thereof, and a view of the basic waveform in Part (D) thereof, in a case where the threshold is fixed when the envelope falls; [0020.9] Fig. 9 is a view illustrating one example of a circuit configuration of a transmission signal generator; [0020.10] Fig. 10 is a block diagram illustrating a configuration of an ultrasonic wave transmitter of an underwater detection apparatus according to a first modification; [0020.11] Fig. 11 shows charts for describing a generation procedure of the drive signal which is generated by a transmission control unit in Fig. 10, in which Part (A) is a chart illustrating a relationship of the counter value outputted from the cycle variable counter with the threshold, Part (B) is a waveform chart of a first pulse wave, Part (C) is a waveform chart of a second pulse wave, and Part (D) is a waveform chart of a combination wave of the first and second pulse waves; [0020.12] Fig. 12 is a block diagram illustrating a configuration of an ultrasonic wave transmitter of an underwater detection apparatus according to a second modification; [0020.13] Fig. 13 is a block diagram illustrating a configuration of a second drive signal generator in Fig. 12; [0020.14] Fig. 14 shows charts illustrating a relationship of a counter value outputted from a cycle variable counter as needed, with a second drive signal generated based on the counter value; [0020.15] Fig. 15 shows a chart of the counter value in Part (A) thereof, a chart of a second drive signal in Part (B) thereof, a view of a transmission waveform based on the second drive signal in Part (C) thereof, and a view of a basic waveform in Part (D) thereof, when an envelope rises; [0020.16] Fig. 16 shows a chart of the counter value in Part (A) thereof, a chart of the second drive signal in Part (B) thereof, a view of the transmission waveform based on the second drive signal in Part (C) thereof, and a view of the basic waveform in Part (D) thereof, when the envelope falls; [0020.17] Fig. 17 is a block diagram illustrating a configuration of an ultrasonic wave transmitter of an underwater detection apparatus according to a third modification; [0020.18] Fig. 18 shows charts for describing a waveform of the drive signal generated by graduafly increasing a step value of the cycle variable counter of the uhrasonic wave transmitter in Fig. 2; [0020.19] Fig. 19 shows charts illustrating a relationship of the counter value outputted from a cycle variable counter of a fifth modification as needed, with a drive signal generated based on the counter value; [0020.20] Fig. 20 is a block diagram illustrating one example of a configuration of a conventional drive signal generator; [0020.21] Fig. 21 shows charts illustrating one example of a drive signal generated by the drive signal generator in Fig. 20; and [0020.22] Figs. 22A and 22B show charts illustrating the drive signal generated by the drive signal generator in Fig. 20 and an envelope of an ultrasonic waveform generated based on the drive signal in correspondence to the drive signal.

Detailed Description

[0021] Hereinafter, one embodiment of an underwater detection apparatus 1 having an ultrasonic wave transmitter 10 according to this disclosure is described with reference to the appended drawings. The underwater detection apparatus 1 detects a target object (e.g., mainly a single fish and a school of fish), and is fixed to a bottom of a ship (e.g., fishing boat) so as to be exposed underwater.

[Overafl Configuration of Underwater Detection apparatus] [0022] Fig. 1 is a block diagram illustrating a configuration of the underwater detection apparatus 1 according to this embodiment of this disclosure. As illustrated in Fig. 1, the underwater detection apparatus 1 includes a transducer 2, a transception device 3, a signal processor 4, and an interface display unit 5 (display unit).

[0023] The transducer 2 has a plurality of ultrasonic oscillators 2a. In the transducer 2, each ultrasonic oscillator 2a transmits underwater an ultrasonic wave converted from an electric signal (transmission signal) at every predetermined timing, receives an ultrasonic wave, and converts the received uhrasonic wave into an electric signal.

[0024] The transception device 3 includes a transception switch 6, a transmission control unit 7. and a receiver 8. The transception switch 6 switches its connection such that in transmission, the transmission signal is transmitted from the transmission control unit 7 to the transducer 2. Moreover, in reception, the transception switch 6 switches its connection such that the electric signal converted from the ultrasonic wave by the transducer 2 is transmitted from the transducer 2 to the receiver 8.

[0025] The transmission control unit 7 outputs, to the transducer 2 via the transception switch 6, the transmission signal generated based on a condition designed by the interface display unit 5. Note that, the transmission control unit 7 constitutes a part of the ultrasonic wave transmitter 10 (described later). A configuration of the transmission control unit 7 is described later in detail.

[0026] The receiver 8 amplifies the signal received by the transducer 2 and AD-converts the amplified reception signal. Then, the receiver 8 outputs reception data obtained from the reception signal convened into the digital signal, to the signal processor 4.

[0027] The signal processor 4 performs processing on the reception daia outputted from the receiver 8 and generates an image signal of the target object.

[0028] The interface display unit 5 displays, on a display screen, an image corresponding to the image signal outputted from the signal processor 4. A user can estimate a state of underwater (e.g., whether the single fish andior the school of fish exists) around the ship by looking at the display screen. Moreover, the interface display unit 5 is provided with an input unit (e.g., various input keys), and various kinds of settings required for the transception of the ultrasonic waves, the signal processing, or the image displaying. and various kinds of parameters can be inputted to the interface display unit 5.

[Configuration of Transmitterl [0029] Fig. 2 is a block diagram illustrating a configuration of the ultrasonic wave transmitter 10 in Fig. 1. The underwater detection apparatus 1 of this embodiment includes the ultrasonic wave transmitter 10. The ultrasonic wave transmitter 10 has the transducer 2 and the transmission control unit 7 described above. Note that, Fig. 2 illustrates a state where the transducer 2 is connected to the transmission control unit 7 by the transception switch 6 in Fig. 1.

[0030] Fig. 3A is a view illustrating one example of a waveform of the ultrasonic wave transmitted from the ultrasonic oscillator 2a. Fig. 3B is a view illustrating one example of a drive signal (first drive signal) that causes the transmission signal for generating the ultrasonic waveform. The ultrasonic oscillator 2a transmits the ultrasonic wave as illustrated in Fig. 3A. Further, the transmission control unit 7 controls an envelope of the ultrasonic waveform transmitted from the ultrasonic oscillator 2a (see Fig. 3A). More specifically, the drive signal has a pulse shape (see Fig. 3B), and the transmission control unit 7 controls an amplitude of the envelope by controlling a width of a pulse wave of the pulse-shaped drive signal that causes the transmission signal for generating the ultrasonic waveform.

[0031] As illustrated in Fig. 2, the transmission control unit 7 includes a cycle variable counter 11, a drive signal generator 20 (first drive signal generator), an envelope controller 12, and a transmission signal generator 15.

[0032] Fig. 4 shows charts illustrating a relationship of a counter value An (n=1, 2. ...) outputted from the cycle variable counter 11 as needed, with the drive signal generated -10-based on the counter value An. As illustrated in Fig. 4, the cycle variable counter Ii increments from an initial value (in this embodiment, zero) by a predetermined step value (i.e., adds the predetermined step value) at a sampling cycle and outputs a counter value (first counter value). When the counter value (the added initial value) becomes higher than a predetermined value A, the counter value becomes the value exceeding the predetermined value A and is incremented again. The cycle variable counter 11 can change the sampling cycle and the step value. Note that, the initial value may also be changed. In this case, after the counter value becomes higher than the predetermined value A once, the incrementing may be started from a value determined based on the amount exceeding the predetermined value A. For example, a lower limit value may he set, and alter the counter value becomes higher than the predetermined value A once, the incrementing may he started from a value obtained by adding the value exceeding the predetermined value A to the lower limit value.

[0033] As illustrated in Fig. 2, the drive signal generator 20 includes a first comparator 21 (comparator), a register 22, a logical conjunction calculator 23, and a timer 26.

[0034] The first comparator 21 compares each counter value An outputted from the cycle variable counter 11 with a threshold Thr, and outputs a comparison result Bn (n=1. 2, ...) thereof. Specifically, when the counter value An is the threshold Thr or lower, the first comparator 21 outputs an OFF signal expressed by "0" in the binary code, and when the counter value is higher than the threshold Thr, the first comparator 21 outputs an ON signal expressed by "I" in the binary code. The comparison result Bn (0 or 1) obtained by the first comparator 21 is outputted to the register 22 and the logical conjunction calculator 23.

[0035] Among the sequentially inputted comparison results from the first comparator 21, the register 22 temporarily stores the latest comparison result. Moreover, when the register 22 receives the next comparison result (here, the comparison result Bn), the register 22 outputs a comparison result Bn-1 to the logical conjunction calculator 23. The comparison result Bn-1 is the comparison result stored before the latest comparison result Bn. In other words, the register 22 stores the latest comparison result, and when the next comparison

-II -

resifit Bn is inputted hereinto, the register 22 outputs, to the ogica conjunction calculator 23, the comparison resull Bn-I stored before the next comparison result Bn.

[0036] The logical conjunction calculator 23 calculates a logical conjunction of the comparison result Bn outputted from the first comparator 21 and a value obtained by inverting the comparison result En-i outputted from the register 22. The logical conjunction calculator 23 outputs the calculation result (0 or 1) to a down counter 24.

[0037] The calculation result of the logical conjunction calculator 23 becomes 1 when the output value from the first comparator 21 is 1 and the output value from the register 22 is 0, which is, to describe with reference to Fig. 4, a case where the counter value (e.g.. Am) inputted hun the first comparator 21 is higher than (exceeds) the threshcild Thr. In other words, when the counter value Am next to a counter va'ue Am-I that is the threshold Thr or lower becomes higher than the threshold Thr, the calculation result of the thgical conjunction calculator 23 becomes 1. In other cases, the calculation result of the logical conjunction calculator 23 becomes 0.

[00381 The timer 26 has the down counter 24 and a second comparator 25.

[0039] The down counter 24 subtracts a predetermined step value from a set value at the sampling cycle and outputs a counter value to the second comparator 25. When the subtracted set value becomes zero, the counter value becomes zero. Specifically, when 1 is inputted into the down counter 24 from the logical conjunction calculator 23, the set value is defined as the counter value, and the counter va'ue is outputted to the second comparator 25.

Then, the counter vakie subtracted by the predetermined step value every time 0 is inputted from the logical conjunction calculator 23 is outputted to the second comparator 25.

[00401 The second comparator 25 compares the counter value outputted from the down counter 24 with a comparison target value (in this embodiment, zero), and generates the drive signal based on the comparison result. Specifically, the second comparator 25 controls the drive signal to be in an ON state when the value from the down counter 24 is not zero, and controls the drive signal to be in an OFF state when the value from the down counter 24 is zero. Thus, as illustrated in Fig. 4, the second comparator 25 outputs the -12-drive signal that becomes ON when the counter value of the cycle variable counter II becomes higher than the threshold Thr and that becomes OFF after a predetermined time period since the drive signal becomes ON. The predetermined time period corresponds to the controlled pulse width.

[0041] The envelope controller 12 includes a threshold controller 13 and a pulse width controller 14.

[0042] The threshold controller 13 controls the numeric value of the threshold Thr which becomes the comparison target value to the counter value outputted from the cycle variable counter 11. The threshold controller 13 controls the threshold Thr to be lower with time when the envelope rises, and controls the threshold Thr to he higher with time when the envelope falls. Moreover, the threshold controller 13 maintains the threshold Thr fixed in a part of the envelope after the rising part and before the falling part (see Fig. 4). Note that, "when the envelope rises" corresponds to a period of time from the amplitude of the envelope starts to increase until the amplitude of the envelope becomes stable. and corresponds to the length of the rising part in Fig. 3A. Moreover, "when the envelope falls" corresponds to a period of time from the amplitude of the envelope starts to decrease until the amplitude of the envelope becomes zero, and corresponds to the length of the falling part in Fig. 3A.

[0043] Fig. 5 shows a chart of the counter value in Part (A) thereof, a chart of the drive signal in Part (B) thereof, a view of a transmission waveform (the waveform of the ultrasonic wave transmitted from the ultrasonic oscillator 2a) in Part (C) thereof, and a view of a basic waveform in Part (D) thereof, in a case where the threshold gradually becomes low when the envelope rises. On the other hand, Fig. 6 shows a chart of the counter value in Part (A) thereof, a chart of the drive signal in Part (B) thereof, a view of the transmission waveform in Part (C) thereof, and a view of the basic waveform in Part (D) thereof, in a case where the threshold is fixed when the envelope rises. Note that, the basic waveform is a waveform with which each of the transmission waveforms in Pan (C) of Fig. 5 and Part (C) of Fig. 6 is compared, and the basic waveform is a constant sine wave of which -13-frequency is fixed.

[0044] For example, as illustrated in Fig. 6, if the threshold Thr is fixed when the envelope rises, the frequency of the drive signal gradually becomes long and gradually shifts from the frequency of the basic waveform. which is because the cycle of the timing at which the level of the drive signal rises is substantially constant, whereas the pulse width of the drive signal gradually becomes long.

[0045] On the other hand, as described above, the threshold controller 13 gradually reduces the threshold Thr when the envelope rises. Thus, the cycle of the timing at which the level of the drive signal rises can be gradually controlled to be short. Therefore, the frequency of the transmission waveform can he kept fixed.

[0046] Fig. 7 shows a chart of the counter value in Part (A) thereof, a chart of the drive signal in Part (B) thereof, a view of the transmission waveform in Part (C) thereof, and a view of the basic waveform in Part (D) thereof, in a case where the threshold Thr gradually becomes high when the envelope falls. On the other hand. Fig. 8 shows a chart of the counter value in Part (A) thereof, a chart of the drive signal in Part (B) thereof, a view of the transmission waveform in Part (C) thereof, and a view of the basic waveform in Part (D) thereof, in a case where the threshold is fixed when the envelope falls, which is different

from the embodiment of the disclosure.

[0047] For example, as illustrated in Fig. 8, if the threshold Thr is fixed when the envelope falls, the frequency of the drive signal gradually becomes short and gradually shills from the frequency of the basic waveform, which is because the cycle of the timing at which the level of the drive signal rises is substantially constant, whereas the pulse width of the drive signal gradually becomes short.

[0048] On the other hand, as described above, the threshold controller 13 gradually increases the threshold Thr when the envelope falls. Thus, the cycle of the timing at which the level of the drive signal falls can be controlled to be gradually long. Therefore, the frequency of the transmission waveform can be kept fixed.

[0049] The pulse width controller 14 controls the pulse width of the drive signal. -14-

Specilically, the pulse width controller 14 controls the pulse width of the drive signal by changing the numeric value of the set value set in the down counter 24. The pulse width controller 14 performs a control of gradually widening the pulse width (in other words, gradually increases the set value) with time when the envelope rises, and performs a control of gradually narrowing the pulse width (in other words, gradually reduces the set value) with time when the envelope falls. Moreover, the pulse width controller 14 maintains the pulse width fixed in the part of the envelope after the rising part and before the falling part.

By controlling the pulse width as above, the amplitude of the envelope can be controlled.

Moreover, the pulse width controller 14 controls the pulse width of the drive signal (i.e., the set value) based on a desired intensity of the ultrasonic wave to be transmitted.

[0050] Fig. 9 is a view illustrating one example of a circuit configuration of the transmission signal generator IS. As illustrated in Fig. 9, the transmission signal generator has a NOT operator (NOT operation part) iSa, two PETs 15b and lSc. and a circuit part lSd having a condenser (not illustrated). In the transmission signal generator 15, the FETs I Sb and I Sc perform switching based on the drive signal inputted into the transmission signal generator 15, a predetermined pulse signal is outputted, the pulse signal is converted into the sine wave-shaped transmission signal by the circuit part lSd, and then the pulse signal is outputted to the transducer 2. Further, the transducer 2 transmits, in response to the transmission signal, the ultrasonic wave with a desired amplitude value of which waveform corresponds to the transmission signal.

[Effects] [0051] As described above, in the ultrasonic wave transmitter 10 of the underwater detection apparatus 1 of this embodiment, the drive signal generator 20 generates the drive signal which becomes the ON state for the predetermined time period since the counter value An becomes higher than the threshold Thr. Thus, the time length for which the drive signal is ON (ON time length) can be fixed. Therefore, variation in the shape the envelope of the ultrasonic waveform caused by variation of the ON time length of the drive signal can he reduced.

[0052] Therefore, with the ultrasonic wave transmiaer 10, the envelope of the ultrasonic waveform can be stabilized.

[00531 Moreover. with the ultrasonic wave transmitter 10, the pulse width controller 14 controls the pulse width of the drive signal by controlling the ON time length of the drive signal. Thus, the envelope of the ultrasonic wave transmitted from the ultrasonic oscillator 2a can suitably be controlled.

[0054] Moreover, with the ultrasonic wave transmitter 10, the threshold is controlled based on the pulse width of the drive signal. Thus, the frequency of the drive signal can suitably he adiusted.

[0055] Moreover, with the ifitrasonic wave transmitter 10, the con1ro of graduafly reducing the threshoki is performed when the env&ope of the ifitrasonic wave rises. Thus, the frequency of the ultrasonic wave can be maintained fixed when the envelope rises.

[0056] Further, with the ultrasonic wave transmitter 10. the control of gradually increasing the threshold is performed when the envethpe of the ultrasonic wave fafis. Thus, the frequency of the ultrasonic wave can be maintained fixed when the envelope falls.

[0057] Moreover, with the ultrasonic wave transmitter 10. the first drive signal generator includes the first comparator 21. the register 22, and the logical conjunction calculator 23.

Thus, the drive signal which becomes the ON state when the counter value is higher than the threshold can suitably he generated.

[00581 Moreover, according to this emhodimenL the underwater detection apparatus which can transmit the ultrasonic wave of which the envelope is stabilized can be structured.

[Modification] [0059] Although the preferred embodiment of this disclosure is described above, this disclosure is not limited to this, and various modifications may be applied within the scope

of this disclosure. -16-

<First Modification> [0060] Fig. 10 is a Hock diagram illustrating a configuration of an ultrasonic wave transmitter iOa of an underwater detection apparatus according to this modification. The ultrasonic wave transmitter lOa of this modification includes a cycle variable counter 11, a first pulse wave generator 20a, a second pulse wave generator 20b, an envelope controller 12, a logical disjunction calculator 16, a transmission signal generator 15, and a transducer 2.

Among these components. the cycle variable counter 11, the transmission signal generator 15, and the transducer 2 have the same configurations as those in the above embodiment,

and therefore, the description thereof is omitted.

[0061] Each of the first and second pulse wave generators 20a and 20h has the same configuration as that of the drive signal generator 20 of the above embodiment. However, in each of the pulse wave generators 20a and 20h, a first threshold Thri and a second threshold Thr2 that are different from each other are set, and the first comparator of the first pulse wave generator 20a compares the counter value with the first threshold Thri, and the first comparator of the second pulse wave generator 20h compares the counter value with the second threshold Thr2.

[0062] Fig. 11 shows charts for describing a generation procedure of the drive signal which is generated by a transmission control unit 7a of the ultrasonic wave transmitter lOa.

Specifically, Part (A) is a chart illustrating a relationship of the counter value outputted from the cycle variable counter Ii with the thresholds Thri and Thr2, Part (B) is a waveform chart of a pulse wave (first pulse wave, first drive signal) generated by the first pulse wave generator 20a, Part (C) is a waveform chart of a pulse wave (second pulse wave, second drive signal) generated by the second pulse wave generator 20b, and Part (D) is a waveform chart of a combination wave of the first and second pulse waves.

[0063] In this modification, the threshold controller 13 controls the values of thresholds Thri and Thr2 such that the second threshold Thr2 becomes higher than the first threshold Thri (see Fig. 11). Specifically, when the cycle of the first pulse wave is T. the threshold controller 13 controls the values of the thresholds Thri and Thr2 such that the second pulse -17-wave delays from the first pulse wave by T/4.

[0064] The logical disjunction calculator 16 generates the combined wave by calculating a logical disjunction of the first and second pulse waves (see Part (D) of Fig. ii). Thus, the transducer 2 transmits the ultrasonic wave generated based on the combined wave. As described above, by transmitting the ultrasonic wave based on the combined wave of the two pulse waves having different phases from each other (the first and second pulse waves), a second harmonic component included in the ultrasonic wave can be reduced. Note that, by controlling the delay of the second pulse wave with respect to the first pulse wave to be T/2k (k=2, 3. 4, ...). a k-th harmonic component in the drive signal can be removed.

Moreover, in this modification, the two pulse waves having different phases from each other are described as an example; however, without limiting to this, the combined wave of three or more pulse waves having different phases from each other may he used to operate the ultrasonic scillator 2a.

[0065] Moreover, a pulse width t when only a desired level is required to be reduced from the output can he expressed by the following Equation 1, using an amplitude u( I) standardized with a maximum amplitude.

[0066] sini () ... (1) <Second Modification> [0067] Fig. 12 is a block diagram illustrating a configuration of an ultrasonic wave transmitter lOb of an underwater detection apparatus according to another modification.

The ultrasonic wave transmitter lOb of this modification includes a cycle variable counter 11, a first drive signal generator 20, a second drive signal generator 30. an envelope controller 12, a drive signal selector 17, a transmission signal generator 15. and a transducer 2. Among these components, the cycle variable counter 11, the transmission signal generator IS, and the transducer 2 have the same configurations as those in the above embodiment, and therefore, the description thereof is omitted. Moreover, the first drive signal generator 20 has the same configuration as that of the drive signal generator 20 of the above embodiment, and therefore, the description thereof is omitted.

[00681 Fig. 13 is a block diagram illustrating a configuration of the second drive signal generator 30. The second drive signal generator 30 includes a third comparator 31, a fourth comparator 32, and a logical conjunction calculator 33.

[0069] Fig. 14 shows charts illustrating a relationship of a counter value outputted from the cycle variable counter 11 as needed. with a second drive signal generated by the second drive signal generator 30 hased on the counter value. Similar to the ahove embodiment, the cycle variable counter II adds the predetermined step value to the initial value at the sampling cycle and outputs a counter value An. When the counter value (the added initial value) becomes higher than a predetermined value A, the counter value An is becomes the value exceeding the predetermined value A and added again.

[0070] The third comparator 31 compares each counter value An outputted from the cycle variable counter 11 with an upper limit threshold Thr_H controlled by the threshold controller 13 (see Fig. 14), and outputs a comparison result thereof. Specifically, when the counter value An is higher than the threshold Thr_H, the third comparator 31 outputs an OFF signal expressed by "0" in the binary code, and when the counter value An is the threshold Thr_H or lower, the third comparator 31 outputs an ON signal expressed by "1" in the binary code.

[0071] The fourth comparator 32 compares each counter value An outputted from the cycle variable counter 11 with a lower limit threshold Thr_L controlled by the threshold controller 13 (see Fig. 14), and outputs a comparison result thereof. Specifically, when the counter value An is lower than the threshold Thr_L, the fourth comparator 32 outputs an OFF signal expressed by "0" in the binary code, and when the counter value An is the threshold Thr_L or higher, the fourth comparator 32 outputs an ON signal expressed by "1" in the binary code. -19-

[0072] The logical conjunction calculator 33 calculates a logical conjunction of the comparison result outputted from the third comparator 31 and the comparison result outputted from the fourth comparator 32. The calculation result obtained by the logical conjunction calculator 33 becomes 1 when the comparison result obtained by the third comparator 31 and the comparison result obtained by the fourth comparator 32 are both 1, which is, to describe with reference to Fig. 14, a case where the counter value An inputted into both of the third and fourth comparators 31 and 32 is between the lower limit threshold Thr_L and the upper limit threshold Thr_H. Thus, as illustrated in Fig. 14, when the counter value becomes the value between the lower limit threshold Thr_L and the upper limit threshold Thr_H, the drive signal outputted from the logical conjunction calculator 33 becomes the ON state until the counter value becomes higher than the upper limit threshold Thr_l-l, and in other cases, the drive signal becomes the OFF state.

[0073] Fig. 15 shows a chart of the counter value in Part (A) thereof, a chart of the second drive signal in Part (B) thereof, a view of a transmission waveform based on the second drive signal in Part (C) thereof, and a view of a basic waveform in Part (D) thereof, when the envelope rises. Moreover, Fig. 16 shows a chart of the counter value in Part (A) thereof, a chart of the second drive signal in Part (B) thereof, a view of the transmission waveform based on the second drive signal in Part (C) thereof, and a view of the basic waveform in Part (D) thereof, when the envelope falls.

[0074] As illustrated in Fig. 15, the threshold controller 13 gradually increases the upper limit threshold Thr_H and gradually reduces the lower limit threshold Thr_L when the envelope rises. Thus, the pulse width can be gradually widened with time while maintaining the cycle of the pulse wave of the second drive signal fixed.

[0075] Moreover, as illustrated in Fig. 16, the threshold controller 13 gradually reduces the upper limit threshold Thr_H and gradually increases the lower limit threshold Thr_L when the envelope falls. Thus, the pulse width can be gradually narrowed with time while maintaining the cycle of the pulse wave of the second drive signal fixed.

[0076] The drive signal selector 17 detects an amplitude value of the ultrasonic wave -20 -transmitted from the ultrasonic oscillator 2a. Further, the drive signa' s&ector 17 selects one of the drive signa's (one of the 1irs and second drive signa's) according to the amplitude value, and outputs the selected drive signal to the transmission signal generator 15. Specifically, the drive signal selector 17 selects the first drive signal when the amplitude value of the ultrasonic wave is lower than a predetermined yalue, and selects the second drive signal when the amplitude value of the ultrasonic wave is the predetermined value or higher.

[0077] The second drive signal may include two kinds of pulses having different pulse widths due to the numeric values of the counter values being discrete. For example. in the case of Fig. 14, the pu'se width of the pulse P2 is sfightly wider than the pulse widths of the pifise P1 and a pulse P3. Thus, when the amplitude value of the ifitrasonic wave is high, by controfling appearance rates of the two kinds of pulses, the envelope contr& can he performed finely. However, when the amplitude value of the ultrasonic wave is low, since the difference between the pulse widths of the two kinds of pulses becomes large, the shape of the envethpe significanfly varies (see Fig. 22).

[0078] On the other hand, since the pulse width of the pulse included in the first drive signal is fixed, even when the amplitude value of the ultrasonic wave is low, the variation of the envelope can be reduced. However, with the first drive signal. since the pulse width is fixed as described, when the amplitude value of the ultrasonic wave is high, the fine envethpe contro' cannot be performed unBke the case of the second drive signal.

[00791 In this regard, the drive signal selector 17 of this embodiment s&ects the second drive signal when the amplitude value of the ultrasonic wave is high. Thus, the fine envelope control can be performed. On the other hand, when the amplitude value of the ultrasonic wave is low, the drive signal selector 17 selects the first drive signal. Thus, the significarn variation of the envelope can be reduced. In other words, in this modification, a suitable control signal (the firsi. control signal or the second control signal) can be selected according to the amplitude value of the ultrasonic wave.

-21 - <Third Modification> [0080] Fig. 17 is a Hock diagram illustrating a configuration of an ultrasonic wave transmitter lOc of an underwater detection apparatus of a third modification. The ultrasonic waye transmitter lOc of this modification is different from the ultrasonic wave transmitter lOb in Fig. 12 in the configuration and operation of the drive signal selectot Specifically, the drive signal selector 17a of this modification detects a rising part and a falling part of the envelope of the ultrasonic waveform (see Fig. 3A). Further, the drive signal selector 17a selects the second drive signal when the envelope of the ultrasonic waveform rises and also when the envelope falls. On the other hand, the drive signal selector 17a selects the first drive signal in the part of the envelope after the envelope rises and before the envelope falls.

[0081] With reference to Fig. 6, when the threshold Thr is maintained fixed when the envelope rises, the cycle of the first drive signal becomes gradually long with time.

Moreover, with reference to Fig. 8, when the threshold Thr is maintained fixed when the envelope falls, the cycle of the first drive signal becomes gradually short with time. In this case, the cycle of the transmission waveform gradually changes. Whereas, while the value of the envelope is stable (in the part of the envelope after the envelope rises and before the envelope falls), since the cycle of the first drive signal becomes fixed, the cycle of the transmission waveform does not vary with time.

[0082] On the other hand, with reference to Fig. 15, with the second drive signal, by performing the control of gradually increasing the upper limit threshold Thr_H and gradually reducing the lower limit threshold Thr_L when the envelope rises, the frequency of the transmission waveform can be maintained fixed. Moreover, with reference to Fig. 16, with the second drive signal, by performing the control of gradually reducing the upper limit threshold Thr_H and gradually increasing the lower limit threshold Thr_L when the envelope falls, the frequency of the transmission waveform can be maintained fixed.

[0083] Thus, by selecting the second drive signal when the envelope rises and also when the envelope falls and selecting the first drive signal while the amplitude value of the -22 -envelope is stable as the drive signal selector 17a of this modification, the shilling of the frequency of the transmission waveform can suitably he reduced.

<Fourth Modification> [0084] Fig. 18 shows charts for describing the waveform of the drive signal generated by gradually increasing the step value of the cycle variable counter 11 of the ultrasonic wave transmitter 10 in Fig. 2. Thus, the transducer 2 can transmit an ultrasonic wave having a so-called chirp waveform. Further, the variation of the pulse width of each pulse of the chirp waveform can be reduced, similar to the case of the above embodiment.

<Fifth Modification> [0085] In the above embodiment, the cycle variable counter II outputs the counter value (first counter value) which is incremented from the initial value by the predetermined step value at the sampling cycle and becomes a value exceeding a predetermined value A when the counter value becomes higher than the predetermined value A; however, it is not limited to this. The cycle variable counter (not illustrated) of this modification decrements from an initial value by the predetermined step value at the sampling cycle and outputs a counter value (second counter value). When the counter value becomes lower than a predetermined value (here, lower than zero), the counter value is decremented from a value obtained by subtracting the value falling below the predetermined value from the initial value (see Fig. i9). Note that, the initial value of this modification may he changed similarly to the above embodiment, and, after the counter value becomes lower than the predetermined value once, the decrementing may be started from a value determined based on the amount falling below the predetermined value, for example, by setting an upper limit value instead of the lower limit. Further, a first drive signal generator (not illustrated) of this modification generates a first drive signal which becomes an ON state when the counter value becomes lower than the threshold Thr. and becomes an OFF state after the predetermined time period since the first drive signal becomes the ON state (see Fig. 19).

-23 -Thus, similar to the above embodiment and the modifications, the drive signal of which the pulse width is fixed can suitably he generated.

<Sixth Modification> [00861 In the above embodiment and the modifications, the example in which the ultrasonic wave transmitter of this disclosure is applied to the underwater detection apparatus is described; however, the application of the ultrasonic wave transmitter is not limited to this. Specifically. the ultrasonic wave transmitter of this disclosure may be applied to an ultrasonic wave diagnosing device configured to diagnose a state of the inside of a human body based on echo signals of ultrasonic waves transmitted into the human body.

Claims

CLAIMS1. An ultrasonic wave transmitter (10) for generating a drive signal to operate an ultrasonic oscillator (2a) and causing the ultrasonic oscillator (2a) to transmit an ultrasonic wave having a desired amplitude value, the ultrasonic wave transmitter (10) comprising: a counter (11) configured to increment from an initial value by a predetermined step value at a sampling cycle and output a first counter value, or decrement from an initial value by a predetermined step value at a sampling cycle and output a second counter value; a first drive signal generator (20) configured to compare the either one of the first and second counter values outputted from the counter (11) with a threshold (Thr) and generate a first drive signal that becomes an ON state when the first counter value is higher than the threshold (Thr) or the second counter value is lower than the threshold (Thr), and then becomes an OFF state after a predetermined time period since the first drive signal becomes the ON state; and a transducer (2) configured to transmit the ultrasonic wave from the ultrasonic oscillator (2a) operated based on the first drive signal, wherein when the first counter value becomes higher than a first predetermined value, the first counter value becomes a value determined based on the amount exceeding the first predetermined value and is incremented again by the predetermined step value, and wherein when the second counter value becomes lower than a second predetermined value, the second counter value becomes a value determined based on the amount falling below the second predetermined value and is decremented again by the predetermined step value.
2. The ultrasonic wave transmitter (10) of claim 1, further comprising a pulse width controller (14) configured to control a pulse width of the first drive signal by controlling the predetermined time period.

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3. The ultrasonic wave transmitter (10) of claim 2, further comprising a threshold controller (13) configured to control the threshold (Thr) according to the pulse width controlled by the pulse width controller (14).
4. The ultrasonic wave transmitter (10) of claim 3, wherein the pulse width controller (14) performs a control of extending the predetermined time period, every time an envelope of the ultrasonic wave rises, and wherein the threshold controller (13) performs a control of reducing the threshold (Thr) every time the envelope of the ultrasonic wave rises in the case where the counter (II) outputs the first counter value, or the threshold controller (13) performs a control of increasing the threshold (Thr) every time the envelope of the ultrasonic wave rises in the case where the counter (11) outputs the second counter value.
5. The ultrasonic wave transmitter (10) of claim 3 or 4, wherein the pulse width controller (14) performs a control of shortening the predetermined time period every time the envelope of the ultrasonic wave falls, and wherein the threshold controller (13) performs a control of increasing the threshold (Thr) every time the envelope of the ultrasonic wave falls in the case where the counter (11) outputs the first counter value, or the threshold controller (13) performs a control of reducing the threshold (Thr) every time the envelope of the ultrasonic wave falls in the case where the counter (11) outputs the second counter value.
6. The ultrasonic wave transmitter (10) of claim 2 or 3, wherein the first drive signal generator (20) includes at least two first drive signal generators (20), wherein the threshold (Thr) includes a first threshold (Thri) and a second threshold (Thr2) higher than the first threshold (Thri), wherein one or more of the first drive signal generators (20) compare the either one -26 -of the first and second counter values with the first threshold (Thr I), wherein the rest of the first drive signal generators (20) compare the either one of the first and second counter values with the second threshold (Thr2), and wherein the ultrasonic oscillator (2a) is operated by the first drive signal generated by the one or more of the first drive signal generators (20) and the first drive signal generated by the rest of the first drive signal generators (20).
7. The ultrasonic wave transmitter (10) of claim 2 or 3, further comprising a second drive signal generator (30) configured to compare the either one of the first and second counter values outputted from the counter (II) with a lower limit threshold (Thr_L) and an upper limit threshold (Thr_H), and generate a second drive signal that becomes an ON state when the either one of the first and second counter values is between the lower limit threshold (Thr_L) and the upper limit threshold (Thr_H), and becomes an OFF state when the either one of the first and second counter values is lower than the lower limit threshold (Thr_L) or higher than the upper limit threshold (Thr_l-l), wherein when the amplitude value of the ultrasonic wave is lower than a predetermined value, the transducer (2) transmits the ultrasonic wave from the ultrasonic oscillator (2a) operated based on the first drive signal, and wherein when the amplitude value of the ultrasonic wave is the predetermined value or higher, the transducer (2) transmits the ultrasonic wave from the ultrasonic oscillator (2a) operated hased on the second drive signal.
8. The ultrasonic wave transmitter (10) of claim 2 or 3, further comprising a second drive signal generator (30) configured to compare the either one of the first and second counter values outputted from the counter (11) with a lower limit threshold (Thr_L) and an upper limit threshold (Thr_H), and generate a second drive signal that becomes an ON state when the either one of the first and second counter values is between the lower limit threshold (Thr_L) and the upper limit threshold (Thr_ll), and becomes an OFF state -27 -when the either one of the first and second counter values is lower than the lower limit threshold (Thr_L) or higher than the upper limit threshold (Thr_U), wherein when the envelope of the ultrasonic wave rises or falls, the transducer (2) transmits the ultrasonic wave from the ultrasonic oscillator (2a) operated based on the second drive signal, and wherein in a part of the envelope of the ultrasonic wave after rising and before falling, the transducer (2) transmits the ultrasonic wave from the ultrasonic oscillator (2a) operated based on the first drive signal.
9. The ultrasonic wave transmitter (10) of any one of claims I to 8, wherein the first drive signal generator (20) includes: a comparator (2!) configured to compare the either one of the first and second counter values outputted from the counter (11) with the threshold (Thr), and output a comparison result thereof; a register (22) configured to receive the comparison result from the comparator (21). store the comparison result, and when the next comparison result is inputted therein from the comparator (21). output the comparison result stored until the next comparison result is inputted; and a logical disjunction calculator (16) configured to calculate a logical disjunction of the comparison result outputted from the comparator (21) and a value obtained by inverting the comparison result outputted from the regisler (22).
10. An underwater detection apparatus (1), comprising the ultrasonic wave transmitter (10) of any one of claims 1 to 9, wherein the underwater detection apparatus (1) detects a target object underwater based on an echo signal of the ultrasonic wave transmitted from the ultrasonic wave transmitter (10).

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ii. A method of operating an ultrasonic oscillator (2a) to cause the ultrasonic oscillator (2a) to transmit an ultrasonic wave having a desired amplitude value, the method comprising: incrementing a counter (11) from an initial value by a predetermined step value at a sampling cycle and outputting a first counter value, or decrementing the counter (11) from an initial value by a predetermined step value at a sampling cycle and outputting a second counter value; comparing one of the first and second counter values outputted from the counter (11) with a threshold (Thr) and generating a first drive signal that becomes an ON state when the first counter value is higher than the threshold (Thr) or the second counter value is lower than the threshold (Thr), and then becomes an OFF state after a predetermined time period since the first drive signal becomes the ON state; and transmitting the ultrasonic wave from the ultrasonic oscillator (2a) operated based on the first drive signal, wherein when the first counter value becomes higher than a first predetermined value, the first counter value becomes a value determined based on the amount exceeding the first predetermined value and is incremented again by the predetermined step value, and wherein when the second counter value becomes lower than a second predetermined value, the second counter value becomes a value determined based on the amount falling below the second predetermined value and is decremented again by the predetermined step value.
12. An ultrasonic wave transmitter substantially as described herein with reference to and as illustrated in the accompanying drawings.
13. A method of operating an ultrasonic transmitter substantially as described herein with reference to the accompanying drawings.-29 -