JPH0743451A - Radar image forming apparatus - Google Patents

Abstract

PURPOSE:To obtain a radar image forming apparatus which can display only an image in a target searching distance by removing secondary echo obtained after predetermined when a pulse is emitted. CONSTITUTION:An any period of a transmitted pulse so set to an ordinary predetermined period to obtain a reflected signal from a searching distance of a target from a transmitter 101 is set to a long period by a long period transmission controller 107. An image from the searching distance of the object received by a receiver 103 in the case of the long period is determined as a image data position in the searching distance of the target by a image position determining unit 111, an image from a far distance in the case of the long period is determined as image data except the target searching distance, and an unnecessary image removing unit 113 removes the image, when following image data of ordinary period includes an image matching with the image data of the determined far distance, as unnecessary image.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radar image forming apparatus, and more particularly to a radar image forming apparatus for removing unnecessary images due to secondary echo.

[0002]

2. Description of the Related Art A pulse radar is a transmitter and a transmitting antenna that radiate a high-frequency transmission signal in a pulse shape by dividing it at regular intervals, and a receiver that receives a reflected wave returning from a target, It is roughly composed of an indicator. Then, the pulse-modulated transmission radio wave hits the target and is reflected in all directions. Among the reflected radio waves, the one coming in the direction of the receiving antenna is received, and the presence of the target is detected and the distance is measured. Done.

The distance to the target can be known by measuring the elapsed time when the transmitted radio wave is emitted and hits the target and returns. For example, if the time from the emission of the transmitted radio wave to its reception is Δt, the distance R to the target is R = c · Δt / 2 c is the speed of light: 3 × 10 ⁸ (m / s) That is, after emitting the transmission pulse, the reflected wave from the target reaches the receiver in a time of Δt = 2R / c.

Then, a transmission radio wave (hereinafter referred to as a transmission pulse) is repeatedly emitted, and at the interval of this repetition, one transmission pulse is emitted and the next transmission pulse is emitted until it hits a distant target and returns. In order to prevent this, the repetition period of the transmission pulse is determined according to the maximum distance of the target to be detected. For example, if the repetition period is short, the reflected wave from a distant target will return after the next transmission pulse appears, so it appears that the target is near the radar. This is a secondary echo, which is often mistaken for the echo of the target object, and the distance may be mistakenly recognized. The relation between the target distance R and the repetition cycle T or the repetition frequency fr is expressed by the following equation as long as the secondary echo or the higher-order echoes are not generated. R = cT / 2 = c / 2fr The distance to the target target was obtained from such a relational expression.

[0005]

However, in the case of a pulse radar, ambiguity remains in the distance measurement due to the repetition frequency. For example, set the pulse interval, which is the pulse repetition period, to 5
If the pulse repetition frequency is 2 KHz at 00 μs (distance: 75 km), then 10 μs (distance: 1.
The echo returning to the receiver after 5 km) cannot be distinguished from the echo returning after 510 μs. The present invention has been made to solve the above problems, and a radar image capable of displaying only an image within a target detection distance by removing a secondary echo obtained after a predetermined time when a pulse is emitted. The purpose is to obtain a production device.

[0006]

A radar image producing apparatus of the present invention forms a pulse of a predetermined cycle based on a set repetition frequency, and emits a transmission pulse of the repetition frequency via a radar antenna. When the transmitter receives a reflection signal from the transmission pulse, it creates an image corresponding to the reflection signal, and also calculates and outputs the distance of the image based on the emission time of the transmission pulse, and the target detection distance. A transmission control unit that sets a normal repetition period for obtaining a video from inside the transmission unit, and a transmission pulse within any one of the transmission pulses set to the normal repetition period to be missed, The long-cycle transmission control unit that makes the cycle of the transmission pulse transmitted from the antenna longer than the normal repetition cycle, and when the transmission pulse is set to the long cycle, the image initially obtained is the short cycle during the long cycle. Reflected by Informs that it is the first image that came,
In addition, the image obtained next is a second image that has been reflected in a long cycle, and a long cycle detection unit that informs that the image and the distance from the reception unit are the image data, and the detection result from the long cycle detection unit is the first image. In the case of video, it is determined as the video data within the target detection distance, and in the case of the second video, it is determined as the video data over the target detection distance. A predetermined number of video data of the time is accumulated, and if there is video data longer than the target detection distance for a long period other than the video data within the fixed target detection distance in this video data, it is removed as a secondary echo and displayed. And an unnecessary image removing unit.

[0007]

According to the present invention, the transmission pulse within any one of the transmission cycles set to the normal repetition cycle is missed so that the cycle of the transmission pulse transmitted from the radar antenna is changed from the normal repetition cycle. Make it a long cycle. (Note that this will be described in this example below, but it is not limited to this. The point is that processing can be performed by changing the cycle.) When the transmission pulse is set to a long cycle, the image initially obtained is At the time of the cycle, it is informed that it is the first image reflected in the short period, and that the image obtained next is the second image reflected in the long period. (Note that this may also be known based on the previous launch time. The point is to know the short / long cycle.) With this detection, the image and distance from the receiving unit are used as image data, and the detection result is In the case of one image, it is decided as the image data within the target detection distance, and in the case of the second image, it is decided as the image data over the target detection distance. When both image positions are determined, if there is image data longer than the target detection distance in the long period other than the image data in the determined target detection distance in the received short period image data, the image is displayed in 2 It is removed and displayed as the next echo.

[0008]

1 is a block diagram showing the concept of the present invention. In the figure, 101 is a transmitter that forms a pulse of a predetermined cycle based on a set repetition frequency and emits a transmission pulse of the repetition frequency via a radar antenna, and 103 receives a reflection signal due to the transmission pulse. At this time, a receiving unit that creates an image corresponding to the reflected signal and calculates and outputs the distance of the image based on the emission time of the transmission pulse, 1
Reference numeral 05 is a transmission control unit that sets a normal repeating cycle for obtaining an image from within the target detection distance in the transmission unit 101. 1
Reference numeral 07 denotes a long cycle in which the transmission pulse within any cycle of the transmission pulse set to the normal repetition cycle is missed to make the cycle of the transmission pulse transmitted from the radar antenna longer than the normal repetition cycle. When the transmission pulse has a long period, the transmission control unit 109 informs that the image obtained first is the first image reflected in the short period in the long period, and the image obtained next is the long image. A long-cycle detector for notifying that it is the second image reflected at a cycle, 111 is a receiver 103
The long period detection unit 1
When the detection result from 09 is the first image, it is decided as the image data within the target detection distance, and when it is the second image, it is decided as the image data over the target detection distance. When the image position is determined, a predetermined number of short-period image data are accumulated and smoothed, and there is image data longer than the target detection distance in the long period other than the image data within the determined target detection distance in this image data. For example, it is an unnecessary image removing unit which is removed as a secondary echo and displayed on the display unit 115.

FIG. 2 is an explanatory view for explaining the concept of the present invention. As shown in the figure, a Ba vessel at a distance R1 of about 50 km from a position A where a radar station is located in the sea area, about 110 K
It is assumed that a Ca ship is located at a distance R2 'of m. In such a case, for example, to catch a Ba vessel, the distance B
Repeat cycle pattern with maximum detection distance (for example, 75 km) (repeating frequency is 2 KHz, repeating cycle is 500 μs)
However, in the present invention, a repeating cycle pattern of a long cycle having a maximum detection distance (repeating frequency of 1 KHz and repeating cycle of 1000 μs) is first fired up to a distance C of 150 km, for example. This long cycle repeat cycle pattern is 2K
It was obtained by missing a pulse with a repetition frequency of Hz. If a transmission pulse of such a long cycle is emitted at time t0 as shown in FIG. 2, for example, time t1
At time t2, the transmission pulse arrives at point B, reaches point C at time t2, and is reflected there, it reaches the radar station at time t4. At this time, in the conventional case, in the case of a long cycle such as the second repeat cycle pattern, the reception processing for the echo from the point B (time t0 to time t2) is not separately performed, but in the present invention, it is shown in FIG. Thus, the reception process is performed, and the images of the ship located at the distance Ba are collected and stored. Next, in the case of a transmission pulse having a repetition frequency of 2 KHz, the pulse is emitted at time t2, but it is missed at time t2. However, in the present invention, the transmission pulse having a long period is not considered, and 2 KHz is used in the previous period of the pulse miss emission.
It is assumed that the transmission pulse of the repetition frequency is transmitted and the reception processing is performed from time t2 to time t4 and stored. That is, the echo between B and C is received. (The point is to receive and store short-distance and long-distance images, which will be described later, but especially for long-distance images.)

Therefore, an image of a ship located at the distance Ca is collected, and the distance is calculated as R from the miss pulse.
The distance is 2. That is, by first emitting a long period transmit pulse, before the secondary echo is received,
Since the images of the ship located at the distance Ba and the ship located at the distance Ca are obtained, the distance between the two ships can be determined. Then, after the time t4, the miss-fire is stopped, the transmission pulse of 2 KHz is emitted again, and the echo from the point B is received and stored. In this case, it is assumed that the pulse emitted at time t4 is reflected by the ship at the distance Ba at time t5, returns to the radar station, and is reflected in the direction of the ship located at the distance Ca. (That is, in this case, from time t4 to time t6, only the image of the ship at the distance Ba is obtained, so the image is processed as a short-distance image.) Therefore, as shown in FIG. 2, from time t7 to time t8. The image of the ship at the distance Ba and the image of the ship at the distance Ca are received at, for example, the image is obtained immediately behind the ship image signal at the distance Ba. That is, when the pulse is emitted at time t6, the ship Ca actually located 110 km away from the radar station is the ship B located at a distance of 50 km.
It is located just behind a. Therefore, in the present invention, the echo of the ship Ba and the echo of the ship Ca are stored by the echo at the time of a long-period transmission pulse, and the distance between the ship Ba and the ship Ca based on the stored echo is accurately calculated. Each received distance is compared, and the stored received video signals at the subsequent short periods are compared, and if the stored received video signals are the distance of Ba, they are output as they are,
If the received video signal stored is Ca, the received video signal is removed.

For example, in the case of FIG. 2, the received video signal of Ca at the time of the fourth, fifth, ... Transmission pulses is removed. Therefore, the image immediately behind the target object Ba is removed. FIG. 3 is a schematic configuration diagram showing an embodiment of the present invention. In the figure, reference numeral 301 is a radar antenna, and reference numeral 303 is a rotation driving unit that notifies the rotation angle per unit time while rotating the radar antenna 301. The transmission unit 101 forms a pulse generation circuit 304 that forms a transmission pulse having a repeating cycle based on a trigger signal, and with the input of the transmission pulse,
At least a oscillating magnetron 306 and a transmission / reception switch 307 that outputs a transmission pulse from the magnetron 306 to the radar antenna 301 and outputs a reception echo from the radar antenna 301 to the receiving unit 103 are provided. Thirty
A trigger generation circuit 8 outputs a trigger signal of the set frequency to the pulse generation circuit 304 of the transmission unit 101 and the reception unit 103 in response to the input of the transmission start instruction. Reference numeral 310 is a miss-fire control circuit. The miss-fire control circuit 310 is set with a miss-pulse pulse number and a trigger pulse width, and the trigger generation circuit 3
When the number of triggers from 08 reaches the number corresponding to the missing pulse number, the circuit is closed for the set trigger pulse width and the trigger signal of the missing pulse number is removed, so that the transmission pulse Stop the output of. When the trigger pulse is removed, the missed-light detection signal is output to a personal computer (hereinafter referred to as a personal computer) described later.
Reference numeral 312 is a timer that measures the time in response to the input of the trigger signal from the trigger generation circuit 308, and is cleared every predetermined time. 314 is the trigger circuit 308 to the receiving unit 10
3 is a pulse counter that counts the trigger pulse output to 3 and outputs the count value to the miss-fire control circuit 310 and the personal computer.

Reference numeral 320 is a personal computer section. PC part 3
In order to remove the secondary echo by inputting the arrival time of the echo from the receiving unit 103, the video signal of the target, and the rotation angle of the radar antenna 301 (hereinafter collectively referred to as video data) from the driving unit 303, 20 is input. At least the program configuration described below is provided. 322 is a memory. The memory 322 stores a plurality of types of normal repetition frequency (or repetition period) patterns and transmission pulse patterns with missing pulses according to the detection distance. The transmission pulse pattern with this missing pulse is, for example, for each rotation of the radar antenna 301, after the transmission pulse having a long period for capturing a target at a long distance is transmitted, and then at a target detection distance. This is a pattern in which short-cycle transmission pulses for capturing a target are sequentially emitted. Further, the target detection distance is obtained when the period is shorter than the long period, and thus the target detection distance is simply referred to as a short distance.
Reference numeral 326 is a transmission pattern extracting means for extracting the transmission pulse selected by the keyboard 324 from the memory 322. Reference numeral 328 denotes the trigger generation circuit 30 which indicates the repetition frequency of the transmission pulse pattern extracted by the transmission pattern extraction means 326.
It is a repetition frequency setting means set to 8.

Reference numeral 330 is a missing-figure decoding means. The missing shot decoding means 330 determines whether there is a missing shot in the extracted transmission pattern, and if there is a missing shot, obtains the number of the missing spot (hereinafter referred to as the missing shot pulse number). , Along with the pulse width, set in the miss-fire control unit 310,
Moreover, since the pulse interval becomes a long cycle due to this missing shot, the time to make this long cycle is found, and the time at which the echo returns from the short-distance section in the obtained long cycle time is the short cycle reception time in the long cycle. Is set in the long period reception detecting means 332. Then, when these settings are completed, a transmission start signal is output to the trigger generation circuit 308. 33
Reference numeral 2 is a long period reception detecting means. Long period reception detecting means 3
When the timer 312 reaches the time set to the long period set by the miss decoding unit 330, it detects that a transmission pulse having a long period is being emitted, and after this detection, the time of the timer 312 is increased. When the set short cycle time is reached, the video data determination means, which will be described later, is notified that the reception time is a short cycle when a long-cycle transmission pulse is received. Further, when the missing-light detection signal is output, the video data determination means is informed that it is a long-period reception time at which an echo from a long distance is received due to the long period.

Reference numeral 336 is a video data judging means. When the video data determination means 336 is notified by the long cycle reception detection means 332 that the reception time is a short cycle in a long cycle, the video data determination means 336 writes an identification code indicating that the reception time is a short cycle in a long cycle in the register and receives it. The video data from the unit 103 is temporarily stored in the register, and when the reception time of the long cycle is notified, an identification code indicating the reception time of the long cycle is written in the register,
The video data from the receiving unit 103 is temporarily stored in the register, and after it is determined that both are aligned, the video data is output to the target position specifying means described later. If it is not indicated that the video data has a long period, the video data is output to the secondary echo removing means described later. Reference numeral 338 is a target position specifying means.
When the identification code determined and stored by the video data determination means 336 is the reception of the short cycle in the long cycle, the target position specifying means 338 determines, based on the arrival time and the angle,
The position of the video data (short distance) when it is received in a short cycle when the long cycle is specified is specified, and when the identification code indicates reception of a long cycle, the missed time and arrival Based on the time and the angle, the position of the video data (which is a long distance) when received in a long cycle is specified.

Reference numeral 340 is a secondary echo removing means. The secondary echo removing unit 340 is the short-distance received data determining unit 33.
If the received data stored in 6 does not have an identification code, it is sequentially stored as video data of a normal cycle (short cycle) corresponding to the pulse number, and the stored video data is accumulated, For example, the smoothed video data and the short-distance video data and the long-distance video data in the long cycle specified by the target position specifying means 338 are compared, and, for example, the video data after the smoothed video data is in the long-distance object. It is removed as video data of secondary echo by the mark and output to the display unit 115. The transmission control unit 105 in FIG. 1 includes a trigger generation circuit 308 and a repetition frequency setting unit 328, and the long cycle transmission control unit 107 includes a missing shot control circuit 310, a missing shot decoding unit 330, a pulse counter 314, and a timer 312. The long cycle detection unit 109 includes a long cycle reception detection unit 332, an injection control circuit 310, and a timer 312.
The image position determination unit 111 includes an image data determination unit 336 and a target position identification unit 338, and the unnecessary image removal unit 113 includes a secondary echo removal unit 340 and image data determination unit 336.
Consists of.

Next, the operation of each section will be described in detail based on the configuration of FIG. 4 to 7 are flowcharts for explaining the operation of the embodiment shown in FIG. The memory 322 has, for example, a short cycle pattern (repetition frequency of 2 KHz and a repetition cycle of 500 μs) for catching the ship B, and a repetition cycle having a long cycle in which any pulse is missed in the short cycle pattern. It is assumed that a pattern (for example, a repetition cycle is 1000 μs, a repetition frequency is 1 KHz) or the like is registered in advance in association with a number. In this state, when the keyboard 324 is operated and, for example, a transmission pattern having a long cycle is selected (S401), the transmission pattern extraction means 326 corresponds to the selection number from the memory 322 and the keyboard 324. A transmission pattern is extracted (S40
3). Next, the repetition frequency setting means 328 sets the repetition frequency fr of the extracted transmission pattern in the trigger generation circuit 308 (S405). Next, the missing-figure decoding unit 330 determines whether or not the extracted transmission pulse has a missing part (S4).
07) If there is a missed shot, the missed pulse number and pulse width are set in the missed shot control circuit 310 (S409).

Next, since the pulse interval becomes a long cycle due to this missing shot, the time for making this long cycle is obtained and set in the long cycle reception detecting means 332 (S411). Next, in the obtained long cycle time, the long cycle reception detecting means 33 sets the reception time received in the short cycle as the short cycle reception time.
It is set to 2 (S413). As a result, since the initial setting is completed, the transmission start instruction is output to the trigger generation circuit 308 and the transmission unit 101 causes the radar antenna 30 to operate.
A radio wave is emitted via 1 (S415). If there is no missing shot in the transmission pulse extracted in step S407,
The control is moved to step S415 to instruct the transmission. In this case, the second pulse in the first cycle is missed, and the transmission pulse is set to have the first cycle as a long cycle. When such a transmission pulse is set, the trigger generation circuit 308 outputs a trigger signal based on the set repetition frequency to the transmission unit 304 and the reception unit 103. The pulse generation circuit 304 of the transmission unit 101 performs pulse modulation according to the output of the trigger signal from the trigger generation circuit 108, and the magnetron 306 oscillates a predetermined high frequency during this pulse width, and the radar via the transmission / reception switch 307. A pulse is emitted from the antenna 301.

At this time, since the pulse generation circuit 308 of the pulse counter 314 is also outputting to the receiving unit 103,
This trigger signal is counted, and similarly, the timer 312 measures time with the input of the trigger signal. Then, as shown in FIG. 5, the long cycle reception detecting means 332 of the personal computer 320 reads the time from the timer 312 (S501) and determines whether it is time to set the long cycle (S50).
3) If it is determined that it is time to set a long cycle, an identification code (for example, a flag) indicating that the transmission pulse is set to a long cycle is set in the register of the video data judging means 336 (S505), and the timer 312 is set. Read the time (S50
7). Next, the long cycle reception detection unit 332 determines whether or not the read time has reached the set short cycle reception time (S509), and when the read time has reached the short cycle time, the long cycle short cycle reception is performed. The identification code indicating that is set in the video data determination means 336 (S511). Next, the long-period reception detection means 332 determines whether or not the missing-light detection signal is input (S513), and when not input, passes control to the video data determination means 336. Then, the video data determination means 336
Determines whether video data is input from the receiving unit 103 (S515). (S517),
Control is moved to step S513. In other words, it is received as a short cycle until there is a missed shot detection.

Next, in step S513, when the missed radiation detection signal is input to the long cycle reception detection means 332, the long cycle reception detection means 332 sets in the video data determination means 336 an identification code indicating reception in the long cycle. Yes (S51
9). Next, the video data determination means 336 determines whether or not there is video data as shown in FIG. 6 (S60).
1) When the video data is input, the video data is written in the register in which the identification code indicating the long-cycle reception is written (S603). And
When the image data is stored in the register in which the two kinds of identification codes are written, the image data determination unit 336 informs the target position specifying unit 338 that both the short distance image data and the long distance image data are prepared. (S605). Next, the target position specifying means 338 smoothes the video data whose identification code indicates reception of a short cycle in a long cycle, and specifies it as the position of the short-range video data within the target detection distance ( S607). In addition, the video data whose identification code indicates long-period reception is smoothed, and its position is specified as long-distance video data (S609).

Then, the secondary echo removing means 340 is notified that the positions of both the near and far image data have been determined (S611), and the control is performed in step S501 shown in FIG.
Move to. That is, the control is transferred to the long cycle reception detecting unit 332. Here, the long-cycle reception detecting means 332 uses the timer 312.
Is read, and it is determined in step S503 whether it is time to make the cycle longer. In this case, it is not a long cycle time. If it is determined that the time is not a long cycle time, it is determined whether the time is a normal cycle (short cycle) (S52).
4) If it is a normal cycle time, a normal cycle (short cycle)
And an identification code indicating that
(S526). Based on this setting, the video data determination means 336 determines whether or not there is video data (S528), and when there is video data, outputs a video creation command to the secondary echo removal means 340 as shown in FIG. Yes (S701).

Next, the secondary echo removing means 340 determines whether the identification code has a normal cycle (short cycle) (S70).
3) If it is a normal cycle (short cycle), the video data is stored in association with the emission pulse number (S705).
Next, it is determined whether or not a predetermined number of transmission pulses have been stored (S707), and if stored, smoothing processing is performed (S709), and the position of the smoothed video data is set to the normal cycle (short cycle). ) Position (S711). next,
The determined short-distance video data and long-distance video data are compared with the normal cycle (short cycle) video data (S71).
3) If there is a video that matches the confirmed long-distance video data in the video data of the normal cycle (short cycle),
The image is removed as the image by the next echo (S715), and output to the display unit 442 for display. Therefore, only the image within the target detection distance is displayed. Next, it is judged whether or not the processing is to be ended (S717), and if not ended, the control is shifted to step S501 in FIG. That is, this process is performed every predetermined number of times. In the above embodiment, the long cycle is realized by removing the trigger signal, but another trigger circuit for generating the long cycle may be provided in advance. (In short, it suffices if the pulse emission cycle changes. Also, the time at which the pulse was emitted last time is stored, and the short / long cycle may be known by checking the difference with the time at which the image was input.)

[0022]

As described above, according to the present invention, any period of the transmission pulse which is set to a normal predetermined period in order to obtain the reflected signal from within the target detection distance is set to a long period, and this long period is set. The image from the target detection distance received at the time of or at the next cycle is determined as the image data position within the target detection distance, and the image from the long distance at the long cycle is determined. If the image data other than the target detection distance is determined, and the image data of the subsequent normal cycle includes an image that matches the determined long-distance image data,
By removing the image as an unnecessary image, the image caused by the pulse reflection emitted last time is removed, so that the ambiguity of the distance measurement can be eliminated.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a concept of the present invention.

FIG. 2 is an explanatory diagram illustrating the concept of the present invention.

FIG. 3 is a schematic configuration diagram showing an embodiment of the present invention.

FIG. 4 is a flowchart illustrating the operation of the embodiment.

FIG. 5 is a flowchart illustrating the operation of the embodiment.

FIG. 6 is a flowchart illustrating the operation of the embodiment.

FIG. 7 is a flowchart illustrating the operation of the embodiment.

[Explanation of symbols]

 101 transmitter 103 receiver 105 transmission controller 107 long-cycle transmission controller 109 long-cycle detector 111 image position determination unit 113 unnecessary image remover 308 trigger generation circuit 310 miss-fire control circuit 328 miss-firing frequency setting means 330 miss-firing decoding Means 332 Long cycle reception detecting means 336 Video data judging means 338 Target position fixing means 340 Secondary echo removing means

Claims (1)

[Claims] 1. A transmission unit that forms a pulse of a predetermined cycle based on a set repetition frequency and emits a transmission pulse of the repetition frequency via a radar antenna, and receives a reflection signal due to the transmission pulse. Then, a video image corresponding to the reflected signal is created, and a receiving unit that obtains and outputs the distance of the video image based on the difference between the emission time of the transmission pulse and the reception time of the reflected signal, and a target detection distance. A transmission control unit that sets a normal repetition cycle for obtaining a video from inside the transmission unit, and a transmission pulse within any cycle of the transmission pulses set to the normal repetition cycle is missed. Or change the cycle,
A long cycle transmission control unit that makes the cycle of the transmission pulse transmitted from the radar antenna longer than the normal repetition cycle, and the transmission pulse is made long cycle by missing or changing the cycle. The first video obtained when
Or, knowing that the difference between the time of the previous launch and the input time of the image is a short period, and notifying that it is the first image reflected in the short period in the long period, and the next obtained image is or the time and the image previously emitted. Long-cycle detection unit that informs that it is the second image reflected at the long cycle by knowing that the input time difference of is a long cycle, and long-cycle detection by using the image and distance from the reception unit as video data. When the detection result from the unit is the first image, it is decided as the image data within the target detection distance, and when the detection result is the second image, the image position confirmation unit is decided as the image data above the target detection distance, When both of the image positions are determined, a predetermined number of the image data in the short cycle is accumulated, and in this image data, the target detection distance of the long cycle other than the image data in the determined target detection distance is equal to or more than the target detection distance. Projection If there is data, radar image creating apparatus characterized by having an unnecessary image removing unit for displaying removed as a secondary echo.