JPH1062526A - Object detecting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an object-detecting apparatus which can stably and precisely detect whether there exists an object or not in a monitoring area without being affected by the extent of the interior or the arrangement state of installed objects. SOLUTION: This apparatus takes out Doppler signal VDPL by mixing the microwave emitted to a monitoring area and the microwave turning back from the monitoring area, the Doppler signal VDPL is sent to a DC amplifier 5 and an AC amplifier 7, and the outputs VDC, VAC of both amplifiers 5, 7 are processed by a microcomputer 9 to judge whether there exists an object or not in the monitoring area. The DC amplifier 5 amplifies a differential signal ΔV of the Doppler signal VDPL and a DC off-set level VD/ A from the microcomputer 9. The microcomputer 9 judges that there exists no object in the monitoring area in the case the output VDC of the DC amplifier is steadily at practically 0V and at this time, the microcomputer 9 turns the VD/ A back to 0V to learn the off-set level of the output VDC of the DC amplifier, and after that, carries out feed-back of the learned value as the DC off-set level VD/ A to the DC amplifier 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an object detecting device for detecting the presence of an object using a Doppler signal.

[0002]

2. Description of the Related Art A moving object detecting apparatus disclosed in Japanese Patent Application Laid-Open No. 2-238884 mixes a radio wave radiated into a monitored space and a reflected wave received from an object in the monitored space, and is generated by moving the object. The Doppler signal is detected, the level of the Doppler signal is compared with a certain threshold, and a moving object is detected based on the time during which the Doppler signal level exceeds the threshold. This conventional device utilizes the fact that the amplitude of a Doppler signal is proportional to the level of a received signal from a moving object, and the frequency of the Doppler signal is proportional to the moving speed of the moving object.

[0003]

One of the uses of the object detecting device is to detect a user in an automatic flushing urinal. In this application, it is important to accurately detect whether or not there is a person in the area immediately in front of the urinal. However, when the above-mentioned conventional apparatus is used for this purpose, even if a person just passes in front of the urinal, it may be mistaken as a user and wasteful washing may be performed.

The cause of the erroneous detection is that the level of the zero amplitude of the Doppler signal, that is, the DC component (hereinafter, referred to as a DC offset level) changes depending on the size of the toilet room and the condition of the installed object. The distance to it depends on the situation of the toilet room. For example, referring to the drawing of Japanese Patent Application Laid-Open No. 2-238884, it can be seen that the DC offset level is regarded as zero, but the DC offset level is not zero but a positive value, and varies depending on the indoor conditions. . As a result, the sensitivity of the detection device becomes too high, and a person far away from the urinal may be erroneously detected, and the degree of the erroneous detection differs depending on indoor conditions.

As described above, it is difficult for the conventional apparatus to stably and accurately detect whether or not an object exists within a certain distance.

Accordingly, it is an object of the present invention to provide an object detection device capable of stably and accurately detecting whether or not an object exists within a predetermined distance.

[0007]

The object detecting apparatus of the present invention comprises: means for generating a Doppler signal having an amplitude corresponding to a distance to an object and a frequency corresponding to a moving speed of the object; Means for subtracting a reference value from the level to generate a difference signal; means for detecting the presence or absence of an object within a predetermined distance by comparing the level of the difference signal with a predetermined threshold; Means for updating the reference value based on the level of the Doppler signal or the difference signal when the absence of the reference signal is indicated.

The object detection device updates a reference value in a state where no object is present, and subtracts the reference value from the Doppler signal to determine the presence or absence of the object based on the difference signal. Therefore, even if the DC offset level of the Doppler signal changes according to the indoor situation, the reference value can be updated to the DC offset level, so that a difference signal obtained by removing the influence of the DC offset level from the Doppler signal can be obtained.
Since the presence or absence of the target is determined based on the difference signal, it is possible to clearly distinguish when the target is nearby and stationary and when there is no target. As a result, the presence or absence of the target can be determined with high accuracy.

In a preferred embodiment, when the level of the difference signal does not exceed a predetermined threshold for a predetermined time, it is determined that there is no object. In this state, the DC offset level of the Doppler signal is learned. , The reference value is updated to the learned DC offset level.

The detection means includes a first threshold value for determining the presence or absence of an object within a relatively far first distance, and a presence / absence of an object within a relatively close second distance. Using a second threshold value for determination and the level of the difference signal,
It can be configured to determine the entry of the object into the first distance, the entry of the object into the second distance, and the retreat of the species out of the first distance. An object detection device provided with such a detection means is suitable for use in user detection for automatically cleaning a urinal. That is, if the second distance is set at a place where the user stands immediately before the urinal, and the first distance is set at a place slightly longer than the second distance,
It is possible to judge that the user has approached the urinal, is urinating, and has left the urinal. Flow control can be performed.

[0011] The entry of the object into the first distance can be determined, for example, by comparing the level of the difference signal with a first threshold value. The approach of the object into the second distance is, for example, comparing the level of the differential signal with the second threshold value after determining that the object has entered the first distance. Can be determined by The departure of the object outside the first distance may be performed, for example, by comparing the level of the difference signal with the first threshold value after determining that the object has entered the first or second distance. Can be determined.

The apparatus of the present invention further comprises means for extracting an AC component of the Doppler signal, wherein the detecting means detects the presence or absence of an object within a predetermined distance by using the differential signal and the AC component together. Can be configured. In this case, for example, when the level of the differential signal does not exceed the threshold for a predetermined time, or after the movement of the peak frequency of the AC component is observed after the presence of the object is detected, there is no object. Is determined, the reference value can be updated.

[0013]

FIG. 1 shows an entire configuration of an urinal object detecting apparatus according to an embodiment of the present invention.

The object detecting device 1 is installed inside a urinal or in a wall just above a urinal in a toilet room, and its output is provided by a valve 13 for flowing or stopping flush water to the urinal. Is connected to a valve controller 11 for driving and controlling the valve.

The object detecting device 1 has a sensor 3, a DC amplifier 5, an AC amplifier 7, and a microcomputer 9. The sensor 3 emits microwaves to the space in front of the urinal, receives the microwaves reflected back from an object in the space, and mixes the two microwaves to extract a Doppler signal VDPL. The Doppler signal VDPL output from the sensor 3 is input to the DC amplifier 5 and the AC amplifier 7 at the same time, and the output V of the DC amplifier 5 and the AC amplifier 7 is
DC and VAC are input to the microcomputer 9. The microcomputer 9 outputs the outputs VDC and V of the amplifiers 5 and 7.
By processing the AC, a user of the urinal is detected, and the detection signal is notified to the valve controller 11. The valve controller 11 controls the valve 13 based on the detection signal from the microcomputer 9 so that the washing water flows at the start and end of the small use of the user.

FIG. 2 shows a specific circuit of the DC amplifier 5 and the AC amplifier 7.

The DC amplifier 5 includes a microcomputer 9
, And subtracts the DC offset level VD / A from the Doppler signal VDPL from the sensor 3, amplifies the difference signal ΔV, and outputs it to the microcomputer 9. On the other hand, the AC amplifier 7 has a characteristic of a low-pass removal filter, and has a Doppler signal V
Remove low frequency components (substantial DC component) from DPL,
Only the remaining medium-frequency component (substantial AC component) is amplified and output to the microcomputer 9. Hereinafter, the output VDC of the DC amplifier 5 is referred to as “DC amplified signal”, and the output VAC of the AC amplifier 7 is referred to as “AC amplified signal”.

FIG. 3 shows an example of the waveforms of the DC amplified signal VDC and the AC amplified signal VAC. The upper stage shows the AC amplified signal VAC and the lower stage shows the DC amplified signal VDC. This waveform example is observed when a person approaches the urinal from the front and moves out of the urinal in the lateral direction after urinal use.

As can be seen from this waveform, when the vehicle is unattended, both the DC amplified signal VDC and the AC amplified signal VAC are almost zero.
V is settled. (In fact, because of the processing by the microcomputer 9, in the case of the AC amplified signal VAC, A
The 0 level is set at the middle point of the dynamic range of the C amplifier 7, and therefore, for example, an offset voltage of 1.75V is intentionally applied. Further, in the case of the DC amplified signal VDC, as will be described later, it is not strictly 0 V but a level slightly higher than 0 level, for example, 1.3 V, for technical reasons for measuring the DC offset level. Is to be specified).

When a person approaches, it approaches at a high moving speed, so that both the DC amplified signal VDC and the AC amplified signal VAC have remarkable high frequency components, and the amplitude increases.

During urinal use, since the person moves slowly (for example, body movement or arm movement) immediately before the urinal or is almost still, the AC amplified signal VAC has a medium amplitude with a small amplitude. A frequency component appears, while a medium frequency component appears in the DC amplified signal VDC, but in addition, a low-frequency component having a large amplitude or a DC component having a large level appears remarkably. Thus, during small use, the DC amplified signal VDC and the AC amplified signal V
It shows a waveform clearly different from AC.

At the time of departure, in this example, since the person has left in the horizontal direction, the frequency is slightly increased as compared with the waveform at the time of small use, but the waveform is shifted to the unmanned state at a stretch with the waveform not much different. . If the person leaves backward instead of in the lateral direction, a waveform in which the high-frequency component appears remarkably and the amplitude decreases is observed, as if the waveform at the time of approach was reversed in time.

As can be understood from the above, first, the level of the DC amplified signal VDC can be used for detecting the user of the urinal. That is, it is possible to determine whether or not there is an unmanned person or whether or not there is a person immediately before the urinal, depending on the level (or amplitude) of the DC amplified signal VDC. In this case, it is important to accurately measure the DC offset level and calibrate the DC amplified signal VDC. Second, changes in the amplitude and frequency of the AC amplified signal VAC can be used to detect movement of a person, that is, approach or departure.

In this embodiment, user detection is performed using only the DC amplified signal VDC. In a second embodiment described later, user detection is performed using both the DC amplified signal VDC and the AC amplified signal VAC.

FIG. 4 is a plan view showing a monitoring area set in front of the urinal 15 in this embodiment. Two large and small areas 17 and 19 are set in front of the urinal 15. The smaller area (hereinafter referred to as the second area)
Reference numeral 19 denotes an area immediately before the urinal 15, which is a place where the user stands during urinal use. The larger area (hereinafter referred to as the first area) 17 is recognized as having a high possibility that the person will use the urinal 15 if there is a person in this area. If not, it is an area where it is substantially recognized that there is no person using the urinal 15 (that is, unmanned state).

FIG. 5 shows the first and second areas 17 and 19.
Are threshold values VTH1 and VTH2 used to determine whether or not a person is present based on the level of the DC amplified signal VDC. still,
In FIG. 5, the DC amplified signal VDC has a DC offset level V
Because D / A has been deducted, 0V (strictly 1.3V
(To a degree).

The first threshold value VTH1 is a threshold value for determining the presence or absence of a person in the first area 17. That is, when the amplitude of the DC amplified signal VDC is smaller than the first threshold value VTH1, it is estimated that the vehicle is unmanned.
It is presumed that a person is in the area 17. Second threshold value VTH2
Is a threshold for determining the presence or absence of a person in the second area 19. That is, the amplitude of the DC amplified signal VDC is
When it is smaller than TH2, it is presumed that there is no person in the second area 19, and when it is larger than the second threshold value VTH2, the second area 1
It is presumed that there is a person in 9 (that is, small use).

In this embodiment, the above two threshold values VTH
1. Using VTH2, the microcomputer 9 performs three types of determination processing, namely, an entry determination, a small-use determination, and a leaving determination. FIGS. 6, 7, and 8 show the flow of the entry determination, the small-use determination, and the exit determination, respectively.

The approach determination shown in FIG. 6 is for detecting that a person has entered the first area 17. In the entry determination, first, the level of the DC amplified signal VDC is set to the first threshold V
It is checked whether or not TH1 has been exceeded (S1). As a result, if it does not exceed it, it is presumed that the vehicle is unmanned. During that time, the check in step S1 is repeated periodically (for example, at 5 ms intervals). When the level of the DC amplified signal VDC exceeds the first threshold value VTH1, it is recognized that a person has entered the first area 17 (S2), and the process proceeds to the small use determination shown in FIG.

The small use determination shown in FIG. 7 is for detecting the presence of a person in the second area 19. In this small use determination, first, the level of the DC amplified signal VDC is set to the second threshold V
It is checked whether TH2 has been exceeded (S11). As a result, when it does not exceed, since the person detected in the previous approach determination has not yet entered the second area 19, and there is a possibility that a mere person may pass, the process immediately proceeds to the exit determination (S1).
4). When the level of the DC amplified signal VDC exceeds the second threshold value VTH2, a person recognizes that a person is entering the second area 19 (S12) and turns on the human body sensing signal which is an output signal of the microcomputer 9. (S13). In response to the turn-on of the human body sensing signal, the valve controller 11
3 is opened for a certain time, and the washing water is allowed to flow. After the human body sensing signal is turned on, the process enters the leaving determination shown in FIG.

The departure determination shown in FIG. 8 detects that a person has left the first area 17 and has become unmanned. In this departure determination, first, the level of the DC amplified signal VDC is set to the first level for X seconds (for example, for 40 ms) continuously.
It is checked whether it is equal to or lower than the threshold value VTH1 (S1).
This check is performed, for example, at 5 ms intervals on the DC amplified signal VDC.
Is compared with the first threshold value VTH1 to check eight consecutive times whether the DC amplified signal VDC is equal to or less than the first threshold value VTH1. If the result of the check is negative, it is next checked whether or not the human body sensing signal is on (S22). As a result, if the human body sensing signal is on, it is presumed that a person is in the second area 19, and thus step 21 is repeated again. On the other hand, if the human body detection signal is off, it is presumed that the person is outside the second area but inside the first area, and the process again proceeds to the small use determination (S23).

If the check result in step S21 is affirmative, it is next checked whether or not the human body detection signal is on (S24). As a result, if the human body detection signal is on, it is recognized that a person who has been in the second area 19 until now has left the first area 17 (that is, has become unmanned) (S25), and the human body is detected. The signal is turned off (S26).
In response to the turning off of the human body sensing signal, the valve controller 11 opens the valve 13 for a certain period of time to flush the washing water. After turning off the human body sensing signal, the process returns to the approach determination shown in FIG.

When the human body detection signal is off at step S24, it is presumed that the person detected in the entry determination is merely a passer-by (ie, has become unmanned), and the process is performed as shown in FIG.
The process returns to the entry determination shown in FIG.

In the above-described entry, entry, and exit determination processing, the presence or absence of a person in the first and second areas is determined by comparing the level of the DC amplified signal VDC with a threshold.
In order to make this determination accurately, it is necessary to measure the DC offset level and remove the influence of the DC offset level from the DC amplified signal VDC. For this purpose, in the present embodiment, the microcomputer 9 learns the DC offset level from the DC amplified signal in the unattended state and stores it as a reference value, and this reference value is stored in the DC offset level VD / A is fed back to the DC amplifier 5 and subtracted from the Doppler signal VDPL.

FIGS. 9 and 10 show the flow of processing for the microcomputer 9 to learn the DC offset level. FIG. 9 shows a process for preparing for learning,
FIG. 10 shows the process of actually learning. 9 and 10 are executed at regular intervals (for example, at intervals of 5 ms) separately from the above-described entry, small-use, and departure determination processes.

In the preparation processing shown in FIG. 9, first, it is checked whether or not the learning start flag is off (S31). If it is on, it means that the learning preparation has already been completed. To end. When the learning start flag is off, it means that the learning preparation is not yet completed. Therefore, whether the approach determination is repeated three times in succession (that is, step S1 in FIG. 6 is repeated three times) Is checked (S32). If the result is affirmative, it is presumed that the vehicle is in the unmanned state. Next, it is checked whether the level of the AC amplified signal VAC has fluctuated up to the present time (S33), and the result is also affirmative. If so, it can be determined that the vehicle is unmanned. On the other hand, step S3
When the result of Step 2 or S33 is negative, there is a possibility that the vehicle is not in the unmanned state, and thus this preparation processing is ended.

If the result of step S33 is affirmative and it is determined that the vehicle is in an unmanned state, then the DC shown in FIG.
The offset level VD / A is initialized to 0 V (S3
4). As a result, a voltage (plus value) obtained by actually amplifying the DC offset level of the Doppler signal VDDL as it is appears in the DC amplified signal VDC.

Next, it is confirmed again whether there is a change in the AC amplified signal VAC (S35). If the AC amplified signal VAC fluctuates at this stage, learning of a new reference value is not performed, and the previously learned reference values (the reference value VD / AREF of VDC / A and the reference value VDCREF of VDC) remain unchanged. The process is maintained (S36), and this process ends.

When it is confirmed in step S35 that there is no change in the AC amplified signal VAC, the DC offset level VD / A is increased by a predetermined unit (S37). As a result, the DC amplified signal V
The DC level will drop. Subsequently, a predetermined value at which the DC amplified signal VDC can be regarded as substantially 0 V, for example, 0.1
V, it is checked whether or not it is below (S38).
Then, steps S35 to S38 are repeated until the result of step S38 becomes positive. When the result of step S38 becomes affirmative, that is, when the DC amplified signal VDC becomes substantially 0 V, it is determined that the learning preparation is completed, the learning start flag is turned on (S39), and this processing ends.

At the stage when the learning start flag is turned on by the above learning processing, the DC amplified signal VDC becomes substantially zero.
V, the DC offset level V at that time
D / A is considered to be an appropriate value (that is, the DC offset level of the Doppler signal VDPL). However,
In practice, there is a possibility that the DC offset level VD / A is too large than an appropriate value. Therefore, in the learning process shown in FIG.
Processing is performed so that the offset level VD / A can be set.

In the learning process shown in FIG. 10, first, the AC amplifier 7 and the DC amplifier 5 shown in FIG.
The amplified signal VAC and the DC amplified signal VDC are taken in (S4
1, S42). Next, it is checked whether or not the learning start flag is on (S43). If the learning start flag is off, the learning process is terminated. If it is on, it is checked whether or not the AC amplified signal VAC has a change (S44). If there is a change in the AC amplified signal VAC, learning of a new reference value is not performed, and the previously learned reference values (VD / AREF, VDCREF) are maintained (S4).
5) The learning start flag is turned off (S46), and this process ends.

If there is no change in the AC amplified signal VAC in step S44, it is checked whether the DC amplified signal VDC has exceeded a predetermined value slightly higher than 0V, for example, 1.3V (S47). For example, the DC offset level VDC / A is reduced by a predetermined unit (S48) to increase the level of the DC amplified signal VDC. Then, step S47
Steps S43 to S48 are repeated until the result of (3) becomes positive.

When the result of step S47 is affirmative,
That is, when the DC amplified signal VDC just reaches 1.3 V, the DC amplified signal VDC and the DC offset level VD / A at that time are stored in the memory as the reference value bells VDCREF and VD / AREF (S49). Then, the learning start flag is turned off (S46), and this process ends.

The DC offset level reference value VD / AREF learned in the above learning process is used as the DC offset level VD / A until the next new learning is performed.
Will be fed back. As a result,
Since the DC amplified signal VDC always oscillates around 1.3 V and is always settled to 1.3 V in the unmanned state, the accuracy is high based on the DC amplified signal VDC regardless of the state of the toilet room. User detection can be performed.

Next, a second embodiment of the present invention will be described. In this embodiment, as shown in FIG. 11, FIG. 12, and FIG. 13, the AC amplified signal VAC is used in addition to the DC amplified signal VDC in the entry, small use, and leaving determination.

In the approach determination shown in FIG. 11, first, it is checked whether the DC amplified signal VDC exceeds the first threshold value VTH1 (S
61) If not, it is checked whether the peak level of the AC amplified signal VAC exceeds a predetermined trigger level (S62). Here, the trigger level is the lowest value of the AC amplified signal VA obtained when an object reflecting the microwave exists in the first area. If the peak level of the AC amplified signal VAC is higher than the trigger level, It is estimated that a person exists in the first area 17. Step S
If the check result of both 61 and 62 is negative, it is regarded as an unmanned state, so this check is repeated periodically (for example, at 640 ms intervals). On the other hand, step S6
If the check result of any of 1, 62 is positive,
Since it is considered that a person has entered the first area 17, the process shifts to small use determination (S63).

In the small use determination shown in FIG. 12, a determination process based on the DC amplified signal VDC shown in FIG. 7 (S74 to S77)
In addition, the peak level of the AC amplified signal VAC is equal to a predetermined threshold V for determining that a person is in the second area 19.
It is checked whether THAC has been continuously exceeded for two cycles (one cycle is, for example, 640 ms) (S71).
It recognizes that there is a person in the area 19 (S75) and turns on the human body sensing signal (S76). If the check result in the step S71 is negative, it is checked whether or not the peak level of the AC amplified signal VAC has exceeded the threshold value VTHAC in one of the two cycles (S72). Since there is a possibility that there is a person at 19, a determination process (S74 to S77) based on the DC amplified signal VDC is started,
If both periods have not been exceeded, it can be considered that no person is present in the second area 19, and the process returns to the entry determination (S73).

In the departure determination shown in FIG.
A determination is made based on the amplified signal VAC (S81 to S84),
Next, a determination is made based on the DC amplified signal VDC (S85 and thereafter). In the first half of the AC determination, first, it is checked whether or not the peak level of the AC amplified signal VAC is equal to or lower than the threshold VTHAC (S
81) If it is not below the threshold value VTHAC, it is presumed that there are still people in the second area, so this departure determination is terminated (the departure determination is repeated again 640 ms later). On the other hand, A
If the peak level of the C-amplified signal VAC is equal to or lower than the threshold value VTHAC, it is checked whether the DC determination in step S85 and subsequent steps has already been performed once or more (S82). If the DC determination has already been performed one or more times, there is a great possibility that a person has already left, and thus the DC determination is immediately passed after passing the AC determination.

If the DC determination has not yet been performed once, it is next checked whether or not the peak level of the AC amplified signal VAC in the immediately preceding cycle is larger than the threshold (S83). (Departure determination is repeated again 640 ms later). On the other hand, if the immediately preceding peak level of the AC amplified signal VAC is larger than the threshold value, the frequency spectrum (peak frequency) having the peak power is moved by referring to the frequency spectrum of the AC amplified signal VAC over the past three cycles. It is checked whether or not it has been during three cycles (S84). As a result of this check, if the peak frequency shifts, it can be estimated that the shift is caused by the departure operation of the person, and it is recognized that the person has departed (S
89), the human body sensing signal is turned off (S90). on the other hand,
If the peak frequency has not moved, the DC amplified signal V
The process proceeds to the DC determination to confirm the departure by the DC.

When entering the DC determination, first, it is checked whether or not a predetermined Z seconds have elapsed since the transition to the leaving determination (S85). Here, the Z seconds are, for example, a time period of about several seconds, and after the shift to the departure determination (that is, after the entry of a person into the second area 19 by the small use determination) is performed.
Before the second elapses, it is considered that there is a possibility that the person detected in the small use determination may simply pass without using the small use,
On the other hand, after the elapse of Z seconds, it is considered that the possibility of passing is low and the possibility that a person is doing small use is high. Therefore, if the result of step S85 is within Z seconds, taking into account the possibility that another person will immediately enter following the passing person,
In order to complete the evacuation determination in a short time, an unmanned state (that is, the DC amplified signal VDC
Is checked (S86), and if the result is affirmative, it is recognized as leaving (S89), and the human body sensing signal is turned off (S86).
90). On the other hand, after the elapse of Z seconds, it is checked whether or not the vehicle is unmanned only for a predetermined relatively long time W seconds (S87) in order to reliably perform the departure determination, and if the result is positive. If it is determined that the person has left (S89), the human body sensing signal is turned off (S90).

Also in the second embodiment, the learning process of the DC offset level shown in FIGS. 9 and 10 is executed in a process different from the above-described approach, entry and exit determinations, whereby The determination of entry, use, and exit is performed accurately without being affected by the condition of the toilet room.

Although the embodiment described above is an application of the present invention to urinal user detection, the present invention can also be applied to object detection for various other uses.

[0053]

The object detecting apparatus according to the present invention can stably and accurately detect whether or not an object exists within a predetermined distance without being influenced by the surrounding situation.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration of an urinal object detection device according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of a DC amplifier 5 and an AC amplifier 7;

FIG. 3 is a waveform diagram of a DC amplified signal VDC and an AC amplified signal VAC.

FIG. 4 is a plan view showing two monitoring areas set in front of the urinal 15;

FIG. 5 is a diagram showing thresholds VTH1 and VTH2 used for recognizing whether or not there is a person in the first and second areas 17 and 19 based on the level of the DC amplified signal VDC.

FIG. 6 is a flowchart of entry determination according to the first embodiment.

FIG. 7 is a flowchart of a small use determination according to the first embodiment.

FIG. 8 is a flowchart of a leaving determination according to the first embodiment.

FIG. 9 is a flowchart of a preparation process for learning a DC offset level.

FIG. 10 is a flowchart of a process of learning a DC offset level.

FIG. 11 is a flowchart of entry determination according to the second embodiment.

FIG. 12 is a flowchart of a small use determination according to the second embodiment.

FIG. 13 is a flowchart of a leaving determination according to the second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Object detection device 3 Sensor 5 DC amplifier 7 AC amplifier 8 Microcomputer

Claims (7)

[Claims] 1. A means for generating a Doppler signal having an amplitude corresponding to a distance to an object and a frequency corresponding to a moving speed of the object, and generating a difference signal by subtracting a reference value from a level of the Doppler signal. Means for detecting the presence or absence of an object within a predetermined distance by comparing the level of the difference signal with a predetermined threshold, and means for detecting whether there is no object within the predetermined distance. Means for updating the reference value based on the level of the Doppler signal or the difference signal. 2. The object detection apparatus according to claim 1, wherein said detection means indicates that there is no target object when the level of said difference signal does not exceed said threshold value for a predetermined time. 3. The Doppler signal of the Doppler signal based on the level of the Doppler signal or the difference signal when the determination means indicates that there is no object.
2. The object detection device according to claim 1, wherein a C offset level is learned, and the reference value is updated to the learned DC offset level. 4. A method according to claim 1, wherein said detecting means determines a first threshold value for determining the presence or absence of an object within a relatively long first distance, and a presence or absence of an object within a relatively close first distance. Using a second threshold value for determination, the level of the difference signal, the first threshold value, and the second threshold value, the approach of the object into the first distance and the object into the second distance The object detection device according to claim 1, further comprising: means for determining entry of the object and retreat of the object out of the first distance. 5. A first determination unit that determines whether an object has entered a first distance by comparing the level of the difference signal with a first threshold value, By comparing the level of the difference signal with a second threshold value in response to the first determination unit determining that the object has entered, whether or not the object has entered within a second distance A second determining means for determining, by comparing the level of the difference signal with a first threshold value in response to the first or second determining means determining the entry of the object, And a third determining means for determining whether or not the target object has left outside of the first distance.
The object detection device according to claim. 6. The apparatus according to claim 1, further comprising: means for extracting an AC component of the Doppler signal, wherein the detecting means detects the presence or absence of an object within a predetermined distance by using the difference signal and the AC component together. The object detection device according to claim. 7. When the level of the differential signal does not exceed the threshold for a predetermined time,
The object detection device according to claim 1, wherein, after the movement of the peak frequency of the AC component is observed after the presence of the object is detected, the absence of the object is indicated.