JPH02115783A - Sonar display circuit - Google Patents

Abstract

PURPOSE:To easily discriminate a target by fixing signals of levels lower than a threshold level to a fixed level lower than the threshold level and outputting signals of levels higher than the threshold level as output signals as it is so that the luminance ratio of video can be emphasized. CONSTITUTION:A reception circuit 4 inputs receiving signals 13 and generates video input signals 14. A threshold level comparison control circuit 5 controlled by a threshold level adjuster 11 generates such signals 15 that signal levels lower than a threshold level are fixed to 0V and signals higher than the threshold level are outputted as they are from the signals 14. A sectional peak value detection circuit 7 detects the peak level 17 during a fixed period tau from the signals 15 and outputs the level 17. A correcting value generation circuit 9 calculates a threshold level correcting value 20 from the level value 17 and the output value 19 of the adjuster 11 and gives the value 20 to a subtraction circuit 8. In addition, a delay circuit 6 delays the signals 15 by the half of the period tau and gives the delayed signals to the circuit 8. The circuit 8 generates video output signals 18 by subtracting the correcting value 20 from the delayed video signals 16 and displays video on a CRT 10. A target is discriminated from the luminance level of the video.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a sonar device that emits sound waves underwater, receives echoes from a target object, and identifies targets based on the intensity of the brightness of the sonar device. This invention relates to a display circuit that performs threshold control on signals.

[Prior Art] In a sonar device, in order to remove unnecessary low-level signals that are not a target, such as reverberation, from images, threshold control is performed on video signals, and only signals exceeding that level are filtered out.
A method of displaying on the RT is performed, the threshold of which is controlled by the operator.

Conventionally, this method either displays the video output signal at a level obtained by subtracting a threshold value from the video input signal as shown in Figure 3, or displays only the level portion exceeding the threshold value as shown in Figure 4. The image was displayed at the same level.

Such conventional methods have the following drawbacks. That is, the method shown in FIG. 3 has a drawback that the brightness level of the target displayed in the image changes as the operator changes the threshold level. As a method of compensating for this drawback, as shown in FIG. 4, threshold control was performed while maintaining the original level. However, the method shown in Figure 4
By performing threshold control on two video signals with different levels, the difference in brightness on the video is more emphasized, and the advantage of the method shown in the figure, which is that it becomes easier to identify the video target at the maximum brightness level, is lost. This was a drawback.

[Means for solving the problem] In a sonar display circuit that displays a video signal on a CRT, based on comparison with a set threshold value, a signal at a level below the threshold value is set to a certain level smaller than the threshold value. a circuit that fixes the signal above the threshold value as an output signal at the same level, a circuit that delays the output signal for a certain period of time, and a determination of the output signal that is compared with the set threshold value. a circuit for detecting a peak value within a specified period; and a circuit for correcting a threshold value set corresponding to the peak value and subtracting it from the delayed signal; This is to perform threshold control and display images according to the threshold set by the operator.

[Embodiment] Next, an embodiment of the present invention will be described with reference to FIGS. 1 and 2.

In FIG. 1, at the time of transmission, the pulse output of the transmission circuit 3 is supplied to the transducer 1 via the transmission/reception switching circuit 2, and a sound wave is radiated into the water. An acoustic signal consisting of background noise such as echoes and reverberations from the target is input to a transducer 1, converted to an electrical signal, passed through a transmission/reception switching circuit 2, and given to a reception circuit 4 as a reception signal 13 to receive a video signal. A human power signal 14 is generated.

The video human input signal 14 is processed by a threshold comparison control circuit 5 controlled by a threshold adjuster 11 controlled by an operator.
A signal 15 is generated in which the signal level below the threshold value is fixed at OV and the signal above the threshold value is output as is. The section peak value detection circuit 7 detects and outputs a peak level with a certain time delay from the output signal 15 of the threshold comparison control circuit 5.

The correction value generation circuit 9 generates a threshold correction value 2 from this peak level detection value 17 and the output value 19 of the threshold adjuster 11.
0 is calculated and given to the subtraction circuit 8.

On the other hand, the delay circuit 6 delays the output signal 15 of the threshold value comparison control circuit 5 by half of the fixed period γ set by the section peak value detection circuit 7 and supplies it to the subtraction circuit 8 . Subtraction circuit 8
subtracts the threshold correction value 20 from the delayed video signal 16 to generate a video output signal 18, which is displayed on the CRT 10. The operator identifies the target based on the brightness level of the image.

FIG. 2 shows the state of signals in each part.

In FIG. 2, (a) shows the video input signal 14, and represents the level relationship with the set threshold value 19. (b) shows the output signal 15 of the threshold comparison control circuit 5. Signals below the threshold A are fixed at OV, and signals above the threshold are kept at the same level (in the example in the figure). vl, v2). (C) shows the output signal 17 of the section peak value detection circuit 7, which represents the peak level within a certain period γ. (d) shows the output signal 20 of the correction value generation circuit 9. When the human power level is V, the output is α(1-v/V) A, (α is a coefficient, and ■ is a fixed value). . (e) shows the video output signal 18. Here, negative levels are not displayed on the video.

Through such processing, the ratio of the two signals shown in FIG. 2(b), which was v2/vl, becomes the following equation in FIG. 2(e).

v2-a (1-v2/V)A This is shown in a graph as shown in Figure 6, where the coefficient α, ■
By appropriately selecting and t, the brightness ratio of the image is emphasized more than the level ratio of the input video signal, and the target can be easily identified.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a waveform diagram showing its operation, FIGS. 3 and 4 are diagrams showing operating waveforms of the conventional method, and FIG. 5 is a signal voltage diagram. It is a graph showing a ratio. l ・ ・ ・ ・ ・ − 2 fists φ φ Φ ・ − 3 ・ ◆ ψ ・ ・ 4 ・ ・ Hisashi ・ ・ ・ 5 φ 6 φ ・ ・ ・ 6 ・ ・ φ ・ φ Bō7 ・ φ Kushi ・ ・ ◆ 8 ... ...transmitter/receiver, ...transmission/reception switching circuit, ...transmission circuit, ...reception circuit, ...threshold comparison control circuit, ...delay circuit, ... Sectional peak value detection circuit, ...subtraction circuit, ...correction value generation circuit, ...CRT. ...Threshold adjuster, ...Transmission signal, ...Reception signal, ...Video input signal, Threshold comparison control circuit output signal, 16 Ju 17 ・ 18 ・ 20 ・ ・Delayed video signal; Peak value detection signal; Video output signal; Threshold signal; Threshold correction signal.

Claims (1)

[Claims] In a sonar display circuit that displays a video signal on a CRT, based on a comparison with a set threshold, signals at a level below the threshold are fixed at a constant level smaller than the threshold, and signals above the threshold are A circuit that outputs the output signal as an output signal at the same level, a circuit that delays the output signal for a certain period of time, and a circuit that detects the peak value of the processed output signal within a specified period of time by comparing it with the set threshold value. and a circuit for correcting and subtracting from said delayed signal a threshold value set corresponding to the peak value of said video signal, said circuit comprising: a circuit for correcting and subtracting from said delayed signal a threshold value set corresponding to the peak value thereof; A sonar display circuit characterized by performing threshold control and displaying an image.