JPH08320382A - Object detector and object detecting method - Google Patents

Abstract

PURPOSE: To provide an object detector and a method for detecting an object capable of detecting the object even when the quantity of light illuminating a subject is changed in any way. CONSTITUTION: A subject 6 is irradiated with the illuminating light so modulated by a control signal 8 from a controller 3 by an illuminator 1 as to vary the brightness, the subject 8 in each modulated state is imaged by an imaging unit 2, two video signals 7 in the modulated states are subtracted by a modulation component extractor 4, the extraneous light except the illumination light is removed from the signal 7, only a modulation component signal 9 is extracted, and the object is detected by a detector 5. As a result, the object of all illuminated states can be detected without altering the object detection threshold.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an object detection device using an image signal output from an image pickup device, and more particularly to an object suitable for automatic (unmanned) safety confirmation of an automatic door (gate) opening / closing device in a parking lot or the like. The present invention relates to a detection device and an object detection method.

[0002]

2. Description of the Related Art In recent years, manpower has been reduced in various fields due to cost reduction, lack of manpower, etc., and automation for that purpose has been promoted. For example, although automatic opening / closing devices such as shutters and gates are widely used in entrance / exit management of parking lots, various object detection devices have been proposed in the past to automate (unmanned) safety confirmation in opening / closing devices. ing.

The structure of a conventional object detecting device is shown in FIG. 7 and FIG.
Will be described with reference to. FIG. 7 is a block diagram showing a schematic configuration of a conventional object detection device, which includes an illumination unit 21 and an imaging unit 2.
2, a detection unit 23, an illumination control unit 24, and the like.
The lighting unit 21 receives the lighting control signal 27 from the lighting control unit 24.
And illuminates the subject 25. The subject 25 is photographed by the image pickup unit 22 and input as a video signal 26 to the detection unit 23.

A detecting method in the detecting section 23 of the conventional object detecting apparatus configured as above will be described with reference to FIG. FIG. 8 is a diagram for explaining an object detecting operation in the conventional object detecting device, and FIG. 8A is an image capturing unit 22 when a substantially square subject 25 is located in front of the image capturing unit 22.
Represents the video screen output from. (B) represents a video signal between the horizontal scanning lines AA ′ in (a).
(C) shows a video screen output from the imaging unit 22 when the intensity of illumination light is different for the same subject as in (a). (D) represents a video signal between the horizontal scanning lines BB 'in (c).

First, consider a case where the subject 25 is illuminated mainly by the illumination light of the illumination unit 21. Figure 8 (a)
When a square object 25 is imaged in the center of the screen as shown in, the brightness ratio of the central part of the object 25 is set to "1".
0 "and the brightness ratio of the peripheral part is" 5 ". At this time,
The video signal waveform between AA ′ in (a) is represented as in (b), the video signal output level is 10 in the subject 25 portion, and 5 in the peripheral portion. Then, in order to detect the subject 25 as an object, in order to distinguish the video signal output level of the object part from the video signal output level of the peripheral part,
The intermediate value is set as the object detection threshold. It is determined that there is an object in a portion having a value larger than the object detection threshold and that there is no object in a portion having a smaller value. In this case, if the object detection threshold value is set to "8", the object exists in the part where the video signal level in the central part is "10" and the object exists in the part where the video signal level in the peripheral part is "5". It is judged that it does not exist. In this way, the object is detected.

[0006]

Generally, the subject 25 is illuminated not only by the illumination light of the illumination unit 21 but also by other light (hereinafter referred to as external light), and the illumination level of the external light depends on the situation. Change. For example, consider a case where the illumination light of the illumination unit 21 is strongly illuminated by external light.
(C) is a square object 2 in the center of the screen as in (a).
5 shows a screen when the image of 5 is captured, the illumination level of outside light becomes strong, and for example, the brightness ratio in the central part of the subject 25 is “15”, and the brightness ratio in the peripheral part is “10”. " The video signal waveform between the horizontal scanning lines BB 'is represented as shown in (d), the video signal output level is "15" at the center of the screen, and the video signal output level around the screen is "1".
In this case, the object 25 cannot be detected as an object by setting the object detection threshold value to "8". That is, in the conventional object detection device, the illumination level by external light is constant. If you become stronger than the level,
There has been a problem that the detected video signal output level exceeds the object detection threshold value, and the object cannot be detected.

Further, it is considered that the object can be detected by changing the object detection threshold value according to the change of the illumination level due to the external light. However, in general, it is almost impossible to predict how the ambient lighting level will change, and it cannot be used unless the ambient lighting level changes are known. It was impossible.

The present invention has been made in order to solve the above-mentioned conventional problems, and provides an object detection apparatus and an object detection method capable of detecting an object regardless of how the illumination level by external light changes. It is intended to be provided.

[0009]

In order to achieve the above object, the object detecting device of the present invention irradiates a control means for outputting a modulated control signal, and irradiates a subject with light modulated by the control signal. Illumination means, image pickup means for picking up an image of a subject, modulation component extraction means for extracting only the modulation component image signal from the video signal output from the image pickup part, which is controlled by the control signal, and the modulation component extraction means. A detection means for detecting the presence or absence of an object is provided by the output modulated component image signal.

In the above structure, the modulation component extracting means stores the video signal output from the image pickup means when the storage timing is controlled by the control signal and the illumination means is in the first modulation state. Storage means for controlling the storage timing by the control signal, the second storage means for storing a video signal output from the imaging means when the illumination means is in the second modulation state, and the first storage It is preferable to include subtraction means for extracting a difference between the video signal stored in the means and the video signal stored in the second storage means.

In the above structure, it is preferable that each of the first and second storage means accumulates and stores video signals in a certain period. Further, it is preferable that the light emitted from the illumination means is invisible light.

Further, the object detection method of the present invention illuminates a subject with modulated illumination light including at least first and second states having different brightness, and an image of the subject illuminated in the first state. The video signal illuminated in the second state is subtracted from the signal to remove external light components other than the illumination light. In the above configuration, the video signal of the subject illuminated in the first state and the video signal illuminated in the second state for a certain period are accumulated and stored, respectively, and the accumulated and stored first signal is stored. It is preferable to subtract the video signal illuminated in the second state from the video signal of the subject illuminated in the state. Also,
It is preferable to irradiate invisible light as the illumination light.

[0013]

The control means is composed of, for example, a microprocessor and a memory, and outputs a control signal which is modulated so that the intensity (or brightness) changes. The illuminating means is, for example, an LED, a laser or the like, and depending on the modulation degree of the control signal
For example, the subject is irradiated with light that is modulated so that the brightness changes. The imaging means is, for example, a video camera,
Images of a plurality of subjects are taken according to the degree of modulation of the illumination light. The modulation component extraction means is composed of, for example, a plurality of frame memories, subtractors, etc., performs a subtraction process on a plurality of video signals obtained by the imaging means, and extracts only the modulation component image signal. The detection means is composed of, for example, a microprocessor, a memory, and the like, and detects the presence or absence of an object by whether or not the modulation component image signal exceeds a predetermined threshold value stored in the memory.

Generally, an object is illuminated by external light such as natural light in addition to the illumination light from the illumination means. However, the temporal change of the external light is extremely gradual and the object detection is short. In time, its brightness can be regarded as almost constant. Therefore, for example, the intensity of the illuminating light can be adjusted to 2
The noise component due to outside light is removed by performing subtraction processing on the image signal of the subject obtained by the image pickup means in each changed state, and a modulation component image signal according to the change of illumination light is obtained. . As a result, even if the noise component due to external light is large and all of the video signals obtained by the imaging means exceed a predetermined threshold value, it is possible to detect the object without changing the threshold value.

Further, it is generally known that when video signals are accumulated in a certain period, random noises contained in the video signals cancel each other, resulting in an improvement in S / N ratio. Therefore, the S / N ratio of the stored video signal is improved by accumulating and storing the video signals in a certain period. Therefore, the S / N ratio can be improved also for the modulation component signal which is the difference output between the two signals.

[0016] Further, for example, when it is desired to detect a human subject without being noticed by the other party, by using invisible light such as infrared rays or ultraviolet rays as the illumination light, the detected human being is not noticed. Further, it is possible to detect without giving discomfort to the other party.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the object detecting device of the present invention will be described below with reference to FIGS. First, FIG. 1 shows a schematic configuration of the object detection device in the first embodiment.
In FIG. 1, the object detection device of the present invention includes an illumination unit 1, an imaging unit 2, a control unit 3, a modulation component extraction unit 4, a detection unit 5, and the like. The control unit 3 outputs the control signal 8, and the control signal 8 is input to the two illumination units 1 and the modulation component extraction unit 4. The illumination unit 1 illuminates the subject 6, whose illumination light is modulated by the control signal 8. The imaging unit 2 images the subject 6 and outputs a video signal 7. Here, since the subject 6 is illuminated with the light modulated by the illumination unit 1, the video signal 7 includes a modulation component. Therefore,
In order to extract the modulation component, the video signal 7 is input to the modulation component extraction unit 4. The modulation component extraction unit 4 extracts the modulation component signal 9 from the video signal 7 using the control signal 8. The modulated component signal 9 is input to the detection unit 5, where an object is detected.

Next, FIG. 2 shows an example of a concrete configuration of the modulation component extracting section 4. In FIG. 2, the modulation component extracting unit 4 includes a first frame memory 11 and a second frame memory 1.
2, the subtraction unit 13 and the like. The video signal 7 is input to each of the first frame memory 11 and the second frame memory 12. Here, when the control signal 8 output from the control unit 3 is in the first modulation state, the video signal 7 is fetched and stored in the first frame memory 11.
Further, when the control signal 8 is in the second modulation state, the video signal 7 is fetched and stored in the second frame memory 12.
Correspondingly, the illumination of the subject is also in the first modulation state and the second modulation state. The first output video signal 14 from the first frame memory 11 and the second output video signal 1 from the second frame memory 12
5 is subjected to subtraction processing by the subtractor 13 to obtain the modulation component signal 9.

Next, an example of a method of extracting the modulation component signal and detecting the object will be described with reference to FIGS. 3 to 5. FIG. 3 shows the positional relationship between the illumination unit 1, the image capturing unit 2, and the subject 6 when a square subject is imaged in the center of the screen. 4 and 5 are diagrams showing the object detection procedure in the first and second cases, respectively.

First, as a first example, consider a case where the external light illumination level is 0, that is, the subject 6 is illuminated only by the illumination unit 1. In FIG. 4, (a) shows a case where the level of the illumination light from the illumination unit 1 to the subject 6 is 0 and the level of other external light is 0 as the first modulation state, that is, when the light is not illuminated at all. The image screen by the imaging unit 2 when the subject 6 is imaged is shown. (B) is
In the second state, the level of the illumination light from the illumination unit 1 is 1
In addition, the image screen by the image pickup unit 2 when the level of the outside light is 0 is shown. (C) represents a video signal waveform between horizontal scanning lines CC ′ in the screen in (a). (D) represents a video signal waveform between horizontal scanning lines DD 'in the screen in (b). (E) is obtained by subtracting the output signal waveform of (c) from the output signal waveform of (d).

In the first state, when the level of the illumination light from the illumination unit 1 is set to 0, the subject 6 is not illuminated at all, and the image signal output from the image pickup unit 2 is (a).
As shown in (c), it becomes 0, and the video signal waveform between the horizontal scanning lines C-C 'becomes 0 as shown in (c). This signal is stored in the first frame memory 11 in FIG.
Next, in the second state, when the illumination light level from the illumination unit 1 is set to 1, the brightness ratio is “15” in the part where the subject 6 exists in the center of the screen, and the brightness ratio in the peripheral part. But"
10 ", the brightness ratio of the shadow of the subject edge is" 5 "
Suppose The video signal waveform between the horizontal scanning lines DD 'at this time is as shown in (d), and this signal is stored in the second frame memory 12 in FIG. Then, the signal waveform shown in (e) is obtained by subtracting the signal waveform shown in (c) from the signal waveform shown in (d).

The above arithmetic processing is performed by the first output video signal 14 from the first frame memory 11 to the second output video signal 1 from the second frame memory 12 in FIG.
5 corresponds to the process of subtracting 5 in the subtraction unit 13. As a result, the signal waveform shown in (e) corresponds to the modulation component signal 9. The signal waveform shown in (e) represents the change amount of the video signal when the level of the illumination light of the illumination unit 1 changes from 0 to 1, and the modulation component of the video signal according to the modulation component of the illumination unit 1. Will be extracted. Here, an object can be detected by setting an object detection threshold for the signal waveform shown in (e). In this case, for example, the object can be detected by setting the object detection threshold value to "13".

Next, as a second example, a case where the subject 6 is illuminated by both external light and the illumination unit 1 will be examined. In FIG. 5, (a) shows an image by the image pickup unit 2 when the subject 6 is imaged when the illumination light from the illumination unit 1 to the subject 6 is 0 and the level of other external light is 1 in the first state. Represents a screen. (B) shows a video screen by the imaging unit 2 when the level of the illumination light from the illumination unit 1 is 1 and the levels of other external light are also 1 in the second state.
(C) is a horizontal scanning line EE ′ of the screen in (a)
Represents a video signal waveform between. (D) shows a video signal waveform between horizontal scanning lines FF 'in the screen in (b).
(E) is obtained by subtracting the output signal waveform of (c) from the output signal waveform of (d).

As the first state, the illumination from the illumination unit 1 is set to 0.
In this case, the subject 6 is illuminated with only external light, and the image screen output from the imaging unit 2 has a brightness ratio of “10” in the central portion and brightness in the peripheral portion as shown in (a). The ratio is "5"
Suppose At this time, the video signal waveform between the horizontal scanning lines E-E 'is represented as shown in (c). This signal is stored in the first frame memory 11 in FIG.

Next, consider the case where the level of the illumination light from the illumination unit 1 is set to 1 as the second state. In general,
When the subject 6 is illuminated with two or more types of light,
Since it is considered that the illumination lights are incoherent to each other, the reflected light from the subject 6 can be represented by the sum of the reflected lights from the illumination lights. In this case, the sum of the light from the illumination unit 1 and the light from the outside light is
It is assumed that the brightness of the image screen by the illumination of only the illumination unit 1 in the first example shown in FIG. 4B and the brightness of the image screen by the external light illumination in the second example shown in FIG. 5A are added. You can think. Therefore, as shown in FIG. 5B, the brightness ratio is “25” in the central part, the brightness ratio is “15” in the peripheral part, and the brightness ratio is in the shadow part of the object edge. It becomes "10". The video signal waveform between the horizontal scanning lines F-F 'at this time is expressed as shown in (d). This signal is stored in the second frame memory 12 in FIG.

In the second case, as shown in FIGS. 5C and 5D, a video signal different from that in the first case is obtained. However, from the video signal waveform of FIG.
By subtracting the video signal waveform shown in FIG.
As shown in (e), a video signal waveform similar to the video signal in the first case shown in FIG. 4 (e) is obtained. Therefore, it is not necessary to change the object detection threshold value even if the level of other external light changes.

As described above, according to this embodiment, the subject 6
Since it has a configuration in which the modulated light is radiated to extract the modulated component image signal 9 from the video signal 7 output from the imaging unit 2, the object is detected even when the level of the external light with respect to the subject 6 changes. Objects can be detected without changing the threshold value.

Next, a second embodiment of the object detecting apparatus of the present invention will be described with reference to FIG. Since the schematic configuration of the object detecting device of the second embodiment is similar to that of the first embodiment shown in FIG. 1, its explanation is omitted. The second embodiment differs from the first embodiment in the configuration of the modulation component extracting unit 4.

As shown in FIG. 6, the modulation component extracting section 4 in the object detecting apparatus of the second embodiment is composed of a first frame memory 11, a second frame memory 12 and a subtracting section 1.
3, a first adding unit 16, a second adding unit 17, and the like. The video signal 7 is input to first and second adders 16 and 17, which are installed in front of the first and second frame memories 11 and 12, respectively. The first output video signal 14 from the first frame memory 11 is input to the first adder 16 as another signal, and the addition result with the video signal 7 is output to the first frame. Input to the memory 11. Similarly, the second adder 17 supplies the second frame memory 12 with another signal.
The second output video signal 15 from is input, and the addition result with the video signal 7 is output and input to the second frame memory 12.

Here, as in the first embodiment, when the control signal 8 is in the first state, the first frame memory 11
The output of the first adder 16 is fetched and stored in. Similarly, when the control signal 8 is in the second state, the output of the second adder 17 is fetched and stored in the second frame memory 12. That is, the cumulative sum of the video signals 7 when the control signal 8 is in the first state is calculated and stored in the first frame memory 11. In addition, the control signal 8 accumulates the video signal 7 in the second state and stores it in the second frame memory 12. And the first frame memory 1
1 subtracts the first output video signal 14 from 1 and the second output video signal 15 from the second frame memory 12.
To obtain the modulated component signal 9.

With this configuration, the signals stored in the first and second frame memories 11 and 12 are accumulated video signals. It is generally known that when video signals are accumulated over a certain period of time, random noises contained in the video signals cancel each other out, resulting in an improved S / N ratio. Therefore, the S / N ratio of the first output video signal 14 from the first frame memory 11 and the second output video signal 15 from the second frame memory 12 is higher than that of the video signal 8. ing. Therefore, the S / N is also applied to the modulation component signal 9 which is the difference output between the two signals.
The ratio can be improved.

As described above, according to the second embodiment, since the S / N ratio of the video signal can be improved, an object detecting device that is strong against external noise factors can be obtained. Also S /
By improving the N ratio, it is possible to increase the object detection sensitivity, and it is possible to reduce the level of the modulated illumination light with respect to the subject. This has the advantage of saving energy and making it difficult to notice the fact that the object being detected is being detected.

For the modulated illumination of the subject in each of the above embodiments, infrared rays or ultraviolet rays can be used instead of visible light. For example, when targeting humans, you may want to detect it without being noticed by the other person, but by using infrared rays or ultraviolet rays for lighting,
This is very useful because the detection can be performed without being noticed by the person being detected and without causing discomfort to the other party.

[0034]

As described above, according to the object detecting apparatus of the present invention, the control means for outputting the modulated control signal, and the illuminating means for irradiating the subject with the light modulated by the control signal are provided. An image pickup unit for picking up an image of a subject, a modulation component extraction unit that is controlled by the control signal, extracts only a modulation component image signal from a video signal output from the image pickup unit, and a modulation output from the modulation component extraction unit. Since the detection means for detecting the presence / absence of an object is provided by the component image signal, the intensity of the illumination light can be obtained even when the subject is illuminated by external light such as natural light in addition to the illumination light by the illumination means. Are modulated, and the video signal of the subject obtained by the image pickup means in each modulated state is subtracted to remove the noise component due to the external light, and the modulated component image signal according to the change of the illumination light is obtained. Rukoto can. As a result, even if the noise component due to external light is large and all of the video signals obtained by the imaging means exceed a predetermined threshold value, it is possible to detect the object without changing the threshold value.

The storage timing of the modulation component extraction means is controlled by the control signal, and the first storage means stores the video signal output from the imaging means when the illumination means is in the first modulation state. Means, second storage means for storing a video signal output from the image pickup means when the lighting means is in the second modulation state, and storage timing is controlled by the control signal, and the first storage means. By providing a subtraction unit for extracting a difference between the stored video signal and the video signal stored in the second storage unit,
The modulation of the illumination light by the illumination means and the storage timing of the first and second storage means, for example, the frame memory can be easily synchronized. In addition, a clock generating means or the like for obtaining the storage timing is unnecessary, and the circuit configuration can be simplified.

Further, by accumulating and storing the video signals for a certain period in the first and second storage means, random noises contained in the video signals cancel each other, and the S / It is possible to improve the N ratio, and as a result, it is possible to improve the S / N ratio also for the modulation component signal that is the differential output of both signals.

Further, by making the light emitted from the illuminating means invisible light, for example, when it is desired to detect a human subject without being noticed by the other party, the invisible light such as infrared rays or ultraviolet rays is used as the illumination light. By using
It is possible to detect without being noticed by the person being detected and without giving discomfort to the other person.

According to the object detecting method of the present invention, the object is illuminated with the modulated illumination light including at least the first and second states having different brightness, and the object illuminated in the first state is illuminated. Since the video signal illuminated in the second state is subtracted from the video signal of, the external light component other than the illumination light is removed.

Further, the image signal of the object illuminated in the first state and the image signal illuminated in the second state for a certain period are accumulated and stored, respectively, and the accumulated and stored first signal is stored. By subtracting the video signal illuminated in the second state from the video signal of the subject illuminated in this state, random noises contained in the video signal cancel each other out, and the S / N of the stored video signal is canceled.
It is possible to improve the ratio, and as a result, it is possible to improve the S / N ratio also for the modulation component signal that is the differential output of both signals.

Further, by irradiating invisible light as the illumination light, for example, when it is desired to detect a human subject without being noticed by the other party, use invisible light such as infrared rays or ultraviolet rays as the illumination light. Thus, the detection can be performed without being noticed by the detected person and without giving discomfort to the other person.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a first embodiment of an object detection device of the present invention.

FIG. 2 is a block diagram showing an example of the configuration of a modulation component extraction unit in the object detection device of the first embodiment.

FIG. 3 is a diagram showing a positional relationship between a subject, a lighting unit, and an imaging unit in the first embodiment.

FIG. 4 is a diagram for explaining an object detecting operation in the first embodiment, and FIG. 4A is a first modulation state in which the level of illumination light from the illumination unit to the subject is 0 and other external light is emitted. A state in which the level is 0, that is, an image screen by the image pickup unit when an object is imaged in the case where no light is illuminated, (b) is a second state, in which the level of the illumination light from the illumination unit is 1, and other The image screen by the image pickup unit when the level of external light is 0, (c) is the image signal waveform between the horizontal scanning lines CC ′ of the screen in (a), and (d) is the image in (b). The video signal waveform between the horizontal scanning lines DD ′, (e) represents the output signal waveform of (d) minus the output signal waveform of (c).

FIG. 5 is a diagram for explaining an object detection operation in the first embodiment, and FIG. 5A is a first state in which the illumination light from the illumination unit to the subject is 0 and the level of other external light is The image screen by the image pickup unit when the object is imaged in the case of 1, and (b) is the image pickup unit when the level of the illumination light from the illumination unit is 1 and the level of the other external light is 1 in the second state. According to FIG. 7, (c) is a video signal waveform between horizontal scanning lines EE ′ of the screen in (a), (d) is a video signal between horizontal scanning lines FF ′ of the screen in (b). The waveform, (e) represents the output signal waveform of (d) minus the output signal waveform of (c).

FIG. 6 is a block diagram showing an example of the configuration of a modulation component extraction unit in the object detection device of the second embodiment.

FIG. 7 is a block diagram showing a schematic configuration of a conventional object detection device.

8A and 8B are diagrams for explaining object detection in a conventional object detection device, FIG. 8A is a video screen output from the imaging unit when a substantially square subject 2 is located in front of the imaging unit, and FIG. ) Is a video signal between horizontal scanning lines AA ′ in (a), (c) is a video screen output from the imaging unit when the intensity of illumination light is different for the same subject as in (a), ( d) is the horizontal scanning line BB ′ in (c)
Represents a video signal in the interval.

[Explanation of symbols]

 1: Illumination unit 2: Imaging unit 3: Control unit 4: Modulation component extraction unit 5: Detection unit 6: Subject 7: Video signal 8: Control signal 9: Modulation component signal 11: First frame memory 12: Second Frame memory 13: Subtractor 14: First output video signal 15: Second output video signal

Claims (7)

[Claims] 1. A control unit for outputting a modulated control signal, an illuminating unit for irradiating the subject with light modulated by the control signal, an image pickup unit for picking up an image of the subject, and a control unit controlled by the control signal. A modulation component extracting unit that extracts only the modulation component image signal from the video signal output from the image pickup unit, and a detection unit that detects the presence or absence of an object by the modulation component image signal output from the modulation component extracting unit. Object detection device. 2. The storage timing of the modulation component extraction means is controlled by the control signal, and the illumination means is a first storage element.
In the modulation state, the first storage unit stores the video signal output from the image pickup unit, and the storage timing is controlled by the control signal, and is output from the image pickup unit when the illumination unit is in the second modulation state. Second storage means for storing the stored video signal, and subtraction means for extracting the difference between the video signal stored in the first storage means and the video signal stored in the second storage means. The object detection device according to claim 1. 3. The object detection apparatus according to claim 2, wherein the first and second storage means respectively store and store video signals for a predetermined period. 4. The object detection device according to claim 1, wherein the light emitted from the illumination means is invisible light. 5. A first and a second having at least different brightness.
Illuminate the subject with modulated illumination light including the state of
Subtracting the video signal illuminated in the second state from the video signal of the subject illuminated in the first state,
An object detection method for removing external light components other than the illumination light. 6. A video signal of a subject illuminated in the first state and a video signal illuminated in the second state are accumulated and stored for a certain period of time, and the accumulated first signal is stored. The object detection method according to claim 5, wherein the image signal illuminated in the second state is subtracted from the image signal of the object illuminated in the state. 7. The object detection method according to claim 5, wherein invisible light is emitted as the illumination light.