JP2008141251A - Detection system and signal processing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a detection system capable of detecting the state of a light source or of a subject irradiated with a light by the light source, and to provide a signal processing method therefor. <P>SOLUTION: The detection system allows the luminance of a light source 11 in an electric charge accumulating time of an imaging device 12 to vary by 4n fold field period of the imaging device 12, and obtains a luminance signal for each n-field per field unit. For this luminance signal, an operating section A131 and an operating section B132 obtain the time average of the difference in level of the luminance signal level in a projection region of m-th and (m+2)-th fields, respectively. An operation processing section 133 obtains a square sum of the values of the time average, and a determining section 134 determines the state of a subject, depending on the value of the square sum. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a detection system that detects the state of a subject using an imaging device or the like, and a signal processing method thereof, for example.

For example, an imaging apparatus used in a nighttime crime prevention system shown in Patent Document 1 has a signal processing unit, and a light source having a frequency of 100 Hz or 120 Hz (when a commercial power source of 50 Hz or 60 Hz is used as the power source, the light source is twice that The brightness varies at 100 Hz or 120 Hz), and a detection unit for detecting the high-frequency modulation signal is provided in the signal processing unit. However, this imaging apparatus must have a frame rate higher than its modulation frequency.
Japanese Patent No. 3019309

  By the way, a standard called NTSC (National Television Standards Committee) system or PAL (Phase Alternating Line) system is adopted for imaging apparatuses which are widely spread in general. Since an image pickup apparatus adopting such a standard has a low frame rate, for example, it cannot be used as an image pickup apparatus of a security system as shown in Patent Document 1.

  An object of the present invention is to provide a detection system capable of detecting the state of a light source or a subject irradiated with the light source and a signal processing method thereof.

  A detection system according to a first aspect of the present invention includes a light source, an imaging device that images the light source or a subject irradiated by the light source, and a signal processing unit that processes a signal acquired from the imaging device. The luminance of the light source changes at a predetermined cycle of the scanning plane period of the imaging device, and the signal processing unit acquires the signal from the imaging device for each predetermined scanning plane cycle, and between a plurality of different scanning planes. The time average of the signal level difference is obtained from the signal level difference of the signal, and a predetermined calculation is performed based on the value of the time average, and the state of the subject is determined according to the value of the calculation result of the calculation. Detect.

  Preferably, the imaging device is a field accumulation, interlace scanning type, and the light source changes in luminance by 4n (n = 1, 2, 3,...) Times the field period of the imaging device. The processing unit includes first and second calculation units and a determination unit that determines the state of the subject. The processing unit acquires the signal for each n fields in units of fields, and the signal is the first and the second. The first arithmetic unit outputs the difference of the signal level in the m (m = 1, 2, 3,...) And (m + 2) th fields in the same area. The second arithmetic unit obtains a second time average of the signal level difference in the (m + 1) th and (m + 3) th fields in the same region, and the determination unit includes: The square sum of the first and second time averages Because, depending on the value of the square sum, it determines the state of the subject.

  Preferably, the imaging device is a frame accumulation, interlace scanning type, and the light source changes in luminance by 4n (n = 1, 2, 3,...) Times the frame period of the imaging device, and the signal The processing unit includes first and second calculation units and a determination unit that determines the state of the subject. The processing unit acquires the signal for every 2n fields in units of fields, and the signal is the first and the second. Each of the first arithmetic units outputs to the second arithmetic unit, and the first arithmetic unit outputs the first signal level difference in the m-th (m = 1, 2, 3,...) And (m + 2) -th fields in the same region. The second arithmetic unit obtains a second time average of the signal level difference in the (m + 1) th and (m + 3) th fields in the same region, and the determination unit includes: Find the sum of squares of the first and second time averages , Depending on the value of the square sum, it determines the state of the subject.

  Preferably, the imaging device is a frame accumulation, non-interlaced scanning type, and the light source changes in luminance by 4n (n = 1, 2, 3,...) Times the frame period of the imaging device. The signal processing unit includes first and second calculation units and a determination unit that determines the state of the subject. The signal processing unit acquires the signal for each n fields in units of frames, and the signal is the first and second calculation units. The first calculation unit outputs the difference of the signal level in the m (m = 1, 2, 3,...) And (m + 2) th frames in the same area. A first time average is obtained, and the second operation unit obtains a second time average of the signal level difference in the (m + 1) th and (m + 3) th frames in the same region, and the determination unit Find the sum of squares of the first and second time averages, Depending on the value of the square sum, it determines the state of the subject.

  A signal processing method for a detection system according to a second aspect of the present invention is a signal processing method for a detection system having an imaging device that images a light source or a subject irradiated by the light source, and the luminance of the light source is determined by the imaging device. From the signal level difference of the signal between a plurality of different scanning planes, a first step of changing the scanning plane period at a predetermined multiple of the scanning plane period, a second step of acquiring a signal from the imaging device every predetermined scanning plane period A third step for obtaining a time average of the signal level difference, a fourth step for performing a predetermined calculation based on the value of the time average, and detecting the state of the subject according to a value of a calculation result of the calculation And a fifth step.

  According to the present invention, it is possible to detect the state of a light source or a subject irradiated on the light source.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a diagram illustrating a configuration example of a detection system according to the present embodiment.

  The detection system 10 includes a light source 11, an imaging device 12, and a signal processing unit 13. The signal processing unit 13 includes, for example, a luminance signal extraction circuit 130, a calculation unit A131 that is a first calculation unit, a calculation unit B132 that is a second calculation unit, a calculation processing unit 133, and a determination unit 134. .

  The light source 11 illuminates the subject with a predetermined luminance. The luminance is variable, and the luminance within the charge accumulation time of the imaging element included in the imaging device 12 changes at a cycle of 4n times the field cycle of the imaging device 12. Here, n = 1, 2, 3,.

The imaging device 12 used in the detection system 10 according to the present embodiment employs an imaging device having the following specifications.
As an example of the imaging device constituting the imaging apparatus 12, a single-plate complementary color filter and a field storage type interline transfer CCD (Charge Coupled Device) image sensor (hereinafter simply referred to as a CCD) are used. As one embodiment, the television system of the imaging apparatus 12 employs the NTSC system, the scanning system employs interlace, the scanning frequency is 15.734 Hz, and the vertical frequency is 59.94 Hz.
The imaging device 12 having such a configuration images the subject irradiated by the light source 11 and outputs a signal obtained by the imaging to the luminance signal extraction circuit 130.

  The luminance signal extraction circuit 130 extracts a luminance signal from the input signal and outputs this luminance signal to the arithmetic unit A131 and the arithmetic unit B132. The calculation unit A131 obtains the time average of the level difference of the luminance signal in the m-th and (m + 2) -th fields in the same area of the image sensor for the input luminance signal. The output result A of the calculation unit A131 is output to the calculation processing unit 133. The calculation unit B132 calculates a time average of the level difference of the luminance signal in the (m + 1) th and (m + 3) th fields in the same region of the input luminance signal. The output result B of the calculation unit B132 is output to the calculation processing unit 133. Details of the operations of the arithmetic unit A131 and the arithmetic unit B132 will be described later.

The output result A and the output result B output from the calculation unit A131 and the calculation unit B132, respectively, are input to the calculation processing unit 133. The arithmetic processing unit 133 obtains a square sum value (A ² + B ² ) of the output result and outputs it to the determination unit 134.

Based on the value of the sum of squares (A ² + B ² ) input from the arithmetic processing unit 133, the determination unit 134 determines whether the subject imaged by the imaging device 12 is stationary or moving, for example. Details of the operation of the determination unit 134 will be described later.

Hereinafter, the configuration and function of the detection system according to the present embodiment will be described in detail.
First, the structure of the CCD of the imaging device 12 according to the present embodiment will be described.

  FIG. 2 is a diagram showing an example for explaining the structure of the CCD according to the present embodiment.

The CCD 20 in FIG. 2 is an interline transfer, and includes a photodiode PD21, a vertical transfer CCD22, a horizontal transfer CCD23, and an amplifier 24.
The photodiodes PD21 are arranged in a matrix. The photodiodes PD21 arranged in the vertical line direction are connected to a vertical transfer CCD 22 for transferring charges for each column. The end of each vertical transfer CCD 22 is connected to a horizontal transfer CCD 23 that transfers charges to the amplifying unit. An amplifier 24 is connected to the output side of the horizontal transfer CCD 23.

The video scanning method is interlaced, and one screen is interlaced scanning, and is composed of an odd field and an even field.
First, light enters the photodiode PD21, and charges are accumulated in the photodiode PD21 during the charge accumulation time. During this time, the photodiode PD21 and the vertical transfer CCD 22 are disconnected.
When the charge accumulation time ends, the photodiode PD21 and the vertical transfer CCD 22 are brought into conduction, and the accumulated charge is transferred to the vertical transfer CCD 22. Immediately after this, the photodiode PD21 and the vertical transfer CCD 22 are disconnected, and the next charge accumulation is started in the photodiode PD21. The charges transferred to the vertical transfer CCD 22 are transferred to the horizontal transfer CCD 23 for each horizontal line and input to the amplifier 24.
The frequency until charge is transferred from the vertical transfer CCD 22 to the horizontal transfer CCD 23 for each horizontal line is the horizontal scanning frequency of 15.734 Hz of the CCD 20. When all the charges of the vertical transfer CCD 22 are transferred to the horizontal transfer CCD 23, the vertical transfer CCD 22 and the photodiode PD 21 are again brought into conduction, and the charges of the photodiode PD 21 are transferred to the vertical transfer CCD 22. In the case of a field accumulation CCD, charges are accumulated in the photodiode PD21 by photoelectric conversion, and the transfer frequency until this charge is transferred from the photodiode PD21 to the vertical transfer CCD 22 is 59.94 Hz.

  FIG. 3 is a diagram for explaining the time series of the CCD 20 of FIG.

As shown in FIG. 3, a required time until charge is accumulated in the photodiode PD21 by photoelectric conversion is ΔT1, and a required time until the charge is transferred from the photodiode PD21 to the vertical transfer CCD 22 is ΔT2.
As can be seen from FIG. 3, the light energy incident on the CCD 20 is sampled at the charge accumulation period ΔT = ΔT1 + ΔT2 = (1 / 59.94) seconds while being integrated during the charge accumulation time ΔT1.

Now, the luminance signal of the captured image captured by the imaging device 12 is input to the signal processing unit 13 as illustrated in FIG.
Here, a method for reading out pixels from the CCD 20 (see FIG. 2) according to the present embodiment will be described.

FIG. 4 is a diagram showing an arrangement example of pixels of a single plate complementary color filter type CCD.
FIG. 5 is a diagram showing an example of a combination of color signals in the odd field OFD and the even field EFD.

The color filter of the pixel is composed of Ye (yellow), Cy (cyan), Mg (magenta), and G (green), and is arranged as shown in FIG. Pixels are read by adding the upper and lower pixels. The combination to be added is shifted by one column between the odd field OFD and the even field EFD. Specifically, in the n-th line of the odd field OFD, (C11 + C21), (C12 + C22), (C13 + C23), (C14 + C24), (C15 + C25),... In the n-line of the even field EFD, (C21 + C31), (C22 + C32), (C23 + C33), (C24 + C34), (C25 + C35),...
Therefore, color signals are output in the odd field OFD and the even field EFD as shown in FIG.
In any case, the same color pattern of a combination of Ye, Cy, Mg, and G is repeated in a two-pixel cycle.
In other words, the color signal appears superimposed on a frequency of two pixel periods or more. Therefore, if this color signal is passed through a low-pass filter having a cutoff frequency of two pixel periods, the color signal is lost and only a luminance signal is obtained.
Therefore, luminance information is sampled at a cycle of two pixels.

A projection region REG illustrated by a circle in FIG. 4 shows a state in which an image of a subject by a light source is projected. It is assumed that the pixels C35, C36, C45, C46, C55, and C56 are completely in the projection region REG and are uniformly irradiated with light.
In the odd field OFD, the luminance information is read by a combination of C35, C36, C45, and C46 of the horizontal line (n + 1), and in the even field EFD, by a combination of C45, C46, C55, and C56 of the (n + 1) line of the horizontal line. Is done.

  As described above, the luminance signal among the signals from the imaging device 12 is output to the signal processing unit 13. This luminance signal is input to the arithmetic unit A131 and the arithmetic unit B132, and a predetermined process is performed.

  Next, a luminance signal processing method performed by the calculation unit A131 and the calculation unit B132 will be described with reference to FIG.

  FIG. 6 is a timing chart of the signal processing unit adopting the signal processing method according to the present embodiment.

FIG. 6A is a diagram showing interline scanning of the imaging device 12 and shows a state of either the even field EFD or the odd field OFD. FIGS. 6B to 6E respectively show waveforms W1, W2, W3, and W4 that represent temporal changes in the luminance signal level processed by the signal processing unit 13, and FIG. 6F changes at a constant cycle. It is a figure which shows the waveform W5 of a sine wave.
The odd field OFD and even field EFD scan one frame. That is, as shown in FIG. 6A, one frame is scanned by A and B and C and D.
In the following description, f represents frequency, t represents time, θ represents phase difference, and ω satisfies (ω = 2πf). Note that π is the circumference ratio.

Waveforms W1 and W2 illustrated in FIGS. 6B and 6C are waveforms for deriving functions of waveforms indicated by a waveform W3 and a waveform W4 described later.
A waveform W3 illustrated in FIG. 6D is a time development distribution of a function for obtaining the level difference AC when the luminance level difference between the luminance signal of the A field and the luminance signal of the C field is the level difference AC. Indicates.
A waveform W4 shown in FIG. 6E is a function time for obtaining the level difference BD when the difference in luminance level between the luminance signal of the B field and the luminance signal of the D field is the level difference BD. The development distribution is shown.
Waveform W3 is derived from waveform W1 and waveform W2, and is obtained by adding waveform W1 and waveform W2 and dividing by two. Waveform W4 is derived from waveform W1 and waveform W2, and is obtained by subtracting waveform W1 from waveform W2 and dividing it by 2.

At this time, a time average SAC that is a first time average of the level difference AC is calculated by the arithmetic unit A131 illustrated in FIG. Further, the time average SBD that is the second time average of the level difference BD is calculated by the calculation unit B132.
Specifically, the time average SAC is calculated from the luminance level difference AC between the A field and the C field by a combination of C35, C36, C45, and C46.
Similarly, the time average SBD is calculated from the level difference BD between the B field and the D field by a combination of C45, C46, C55, and C56.

The calculation method of the time average is described.
The time average SAC of the level difference AC between the A field and the C field is calculated by multiplying the waveform W1 by the waveform W3 shown in FIG. 6D.
Similarly, the time average SBD of the level difference BD between the B field and the D field is a waveform representing the time change of the light irradiated to the pixel by the combination of C45, C46, C55, and C56, as shown in FIG. The time average SBD is calculated by multiplying the waveform W4 shown.

First, a method for calculating the time average SAC will be specifically described.
The waveform W3 is expressed by a mathematical expression. First, the waveform W1 and the waveform W2 can be expressed by the following Fourier series.

  Here, it is assumed that the waveforms W1 and W2 have the same period f2. From equation (1) and equation (2), waveform W3 can be expressed as equation (4).

  Incidentally, the waveform W5 having the period f1 shown in FIG. 6F can be represented by a sine wave as shown in the equation (5).

  When the waveform W3 represented by the equation (4) is multiplied by the sine wave W5 represented by the equation (5), the equation (7) is obtained.

Next, the time average of the equation (7) from time 0 to time T is taken. Of the terms shown on the right side of the equation (7), the term including time t is an AC signal, so the time average is zero.
Therefore, only when (ω ₁ − (2n−1) ω ₂ = 0), the constant cos θ ₁ and the constant sin θ ₁ remain, and the time average SAC is expressed by the equation (8).

  In this way, the time average SAC is obtained by the calculation unit A131. Similarly, the time average SBD is obtained by the calculation unit B132 and is expressed by the equation (9).

Now, the sum of squares (S _AC ² + S _BD ² ) of the time average SAC and SBD expressed by the equations (8) and (9) is expressed by the equation (10).

From this equation (10), when the frequency component (f ₁ = (2n−1) f ₂ ) is included in the light incident on the CCD 20 (see FIG. 2), it is expressed by the equation (10). Waveform components are detected.

Next, frequency components included in the light source 11 will be considered.
FIG. 7 is a diagram illustrating a waveform W <b> 6 for the frequency component included in the light source 11. The light source 11 emits light at the luminance level L1 at the frequency f3 for the time τ.

This waveform W6 is developed into a Fourier series. The waveform W6 is a periodic function of a period (T ₃ = 1 / f ₃ ). When (ω ₃ = 2πf ₃ ), the waveform W6 is represented by a general formula of Fourier series as shown in Expression (11).

The coefficients a ₀ , a _n , and b _{n in the} equation (11) are obtained from the waveform W6 as in the equations (12) to (14).

  Therefore, the Fourier series of the waveform W6 is expressed by equation (15).

Therefore, when the blinking period of the light source 11 is set to four times the field period, that is, when (f ₃ = f ₂ ), the frequency coincides with the odd term from the expressions (7) and (15), and the time average SAC And the sum of the squares of SBD is given by equation (16).

  When the duty ratio of lighting of the light source 11 is D, it is expressed by equation (17).

    Therefore, the square sum SACBD of the time average SAC and SBD expressed by the equation (16) is expressed by the equation (18) when the equation (17) is used.

  By the way, the term (19) on the right side of the following equation (18) converges.

  The term (19) on the right side of the equation (18) takes a value as shown in Table 1 with respect to the duty ratio D. Table 1 is shown below.

  Based on Table 1, when the duty ratio D is taken on the horizontal axis and the square sum SACBD of the time average SAC and SBD is taken on the vertical axis, the relationship between the duty ratio D and the square sum SACBD is shown in FIG. become that way.

From FIG. 8, it can be seen that the square sum SACBD becomes maximum at the duty ratio D = 0.5.
Therefore, the sum of squares SACBD expressed by the equation (18) is expressed by the following equation.

(Equation 15)
S _AC ² + S _BD ² = 0.08333L ₁ ² (20)

  As shown in Expression (20), the arithmetic processing unit 133 detects the luminance of the light source 11 (see FIG. 1), and outputs the detection result (square sum SACBD) to the determination unit 134. Based on this detection result, the determination unit 134 determines the state of the subject.

The light source 11 according to the present embodiment does not depend on a specific light source. Therefore, it is considered whether the luminance can be detected for other light sources.
Incandescent light bulbs and fluorescent lamps that are widely used as light sources are 100 Hz in regions where the power supply frequency is 50 Hz and 120 Hz in regions where 60 Hz. The field frequency of an NTSC television is 59.94 Hz, and the field frequency of a monitor used for a personal computer is 60 Hz or more so as not to flicker.

  The field frequency of the NTSC television is 59.94 Hz, and if the light source is caused to emit light at a quarter period, the frequency f2 of the luminance level difference is as follows.

(Equation 16)
f ₂ = 59.94 / 4 = 14.985 Hz (21)

  From the equations (7) and (15), the signal component is detected when the odd multiple of the frequency f2 matches the integer multiple of the frequency f3 of the light source 11.

  Table 2 is a table of values indicating the relationship between the light emission frequency of different light sources and the frequency in the difference in luminance signal level.

F1 in Table 2 is the frequency of the sine wave of Formula (5), f2 is the frequency shown in Formula (21), and f3 is the frequency of the light source 11, the frequency of illumination in the 50 Hz region, and the illumination in the 60 Hz region, respectively. Frequency, NTSC television field frequency, and monitor field frequency used in personal computers.
According to Table 2, up to m = 30, f3 is 100, 120, 59.94 Hz, and there is nothing that satisfies (n × f ₃ = (2m−1) × f ₂ ).

For example, regarding a monitor of a personal computer, if the field frequency is 60 Hz or more, there is a monitor that is scanned at 74.925 Hz as the possibility that the largest output is detected in the signal processing output of the detection system 10. It is time to do. That is, when f ₃ = 74.925 Hz, as shown in Table 2, (5 × f ₂ ), (15 × f ₂ ), (25 × f ₂ ), and (1 × f ₃ ), ( 3 × f ₃ ), (5 × f ₃ ). The signal level detected at this time is expressed by the following equation.

したがって、（２２）式で示される信号レベルは光源１１の１／２５のレベルであり、図1に図示してない信号処理で別に除去できる。

Therefore, the signal level expressed by the equation (22) is 1/25 of that of the light source 11, and can be removed separately by signal processing not shown in FIG.

  As described above, the detection system 10 detects the state of the light source or the subject irradiated on the light source without depending on the light emission frequency of the light source.

  A series of operations in the signal processing method of the detection system according to the present embodiment will be described below with reference to FIG.

  FIG. 9 is a flowchart for explaining the signal processing method of the detection system according to the present embodiment.

In the present embodiment, in the first step (ST1), the luminance of the light source 11 within the charge accumulation time of the imaging device 12 is changed by 4n times the field period of the imaging device 12.
Next, in the second step (ST2), a luminance signal is acquired for each n fields from the imaging device 12 in units of fields, and this luminance signal is output to the arithmetic unit A131 and the arithmetic unit B132.
In the third step (ST3), the arithmetic unit A131 obtains the time average SAC of the level difference AC of the luminance signal level in the projection area REG of the mth and (m + 2) th fields. Further, the arithmetic unit B132 obtains the time average SBD of the level difference BD of the luminance signal level in the projection area REG of the (m + 1) th and (m + 3) th fields. These time averages SAC and SBD are output to the arithmetic processing unit 133.
Subsequently, in the fourth step (ST 4), the arithmetic processing unit 133 obtains the square sum SACBD of the time average SAC and SBD and outputs it to the determination unit 134.
Finally, in the fifth step (ST5), the determination unit 134 determines the state of the subject according to the value of the square sum SACBD.

In the arithmetic processing unit 133 according to the present embodiment, the square sum SACBD of the time average SAC and SBD is obtained, and the sum of the time average SAC and SBD (S _AC + S _BD ) is determined by the determination unit 134. It can also be used.

  As described above, according to the present embodiment, the background noise of the captured image can be removed, and the state of the subject irradiated with the light source or the light source can be detected.

  In addition, the detection system according to the present embodiment captures a signal obtained from the imaging apparatus, processes the signal inside the signal processing unit 13, and detects the state of the subject. It does not depend on the light source. Therefore, it does not depend on the specifications of the imaging apparatus, and for example, a generally available camera can be used as the imaging apparatus of the detection system.

Furthermore, this detection system uses a plurality of light sources and can transmit signals to the signal processing unit in parallel.
Alternatively, it is possible to provide a plurality of light source colors and perform wavelength multiplexing transmission of signals.
Further, the light source can be appropriately blinked to transmit a signal to the signal processing unit.

(Second Embodiment)
Next, a second embodiment according to the present invention will be described.

In this embodiment, the field storage and interlace imaging device 12 according to the first embodiment is replaced with a frame storage and interlace imaging device. At the same time, the luminance change period of the light source 11 according to the first embodiment is changed from 4n times the field period to 4n times the frame period. Accompanying this change in the change period, the luminance signal acquisition period is changed from every n fields to every 2n fields.
In this way, by changing the luminance change cycle of the light source 11 and the luminance signal acquisition cycle, the same effect as in the first embodiment can be obtained.
Therefore, according to the present embodiment, it is possible to remove the background noise of the captured image and detect the state of the light source or the subject irradiated with the light source.

(Third embodiment)
Next, a third embodiment according to the present invention will be described.

In this embodiment, the field accumulation / interlace scanning imaging device 12 according to the first embodiment is replaced with a frame accumulation / non-interlace scanning imaging device.
As described above, even when a non-interlaced scanning imaging apparatus is used, the same effect as that of the first embodiment can be obtained.
Therefore, according to the present embodiment, it is possible to remove the background noise of the captured image and detect the state of the light source or the subject irradiated with the light source.

It is a figure showing an example of 1 composition of a detection system concerning this embodiment. It is a figure which shows an example for demonstrating the structure of CCD which concerns on this embodiment. It is a figure for demonstrating the time series of CCD20 of FIG. It is the figure which showed the example of an arrangement | sequence of the pixel of a single plate complementary color filter type CCD. It is a figure which shows an example of the combination of the color signal in odd field OFD and even field EFD. It is a timing chart of the signal processing part which employ | adopted the signal processing method which concerns on this embodiment. It is a figure which shows the waveform W6 about the frequency component contained in the light source. It is a figure which shows an example of the relationship between duty ratio D and square sum SACBD. It is a flowchart figure for demonstrating the signal processing method of the detection system which concerns on this embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Detection system, 11 ... Light source, 12 ... Imaging device, 13 ... Signal processing part, 130 ... Luminance signal extraction circuit, 131 ... Operation part A, 132 ... Operation part B, 133 ... Operation processing part, 134 ... Determination part.

Claims (5)

A light source;
An imaging device for imaging the light source or a subject illuminated by the light source;
A signal processing unit for processing a signal acquired from the imaging device;
Have
The light source is
The luminance changes at a predetermined cycle of the scanning plane cycle of the imaging device,
The signal processor is
The signal is acquired from the imaging device every predetermined scanning plane period, a time average of the signal level difference is obtained from a signal level difference of the signal between a plurality of different scanning planes, and further, based on the value of the time average A detection system that performs a predetermined calculation and detects the state of the subject according to a value of a calculation result of the calculation. The imaging apparatus is
Field accumulation, interlace scanning type,
The light source is
The luminance changes by 4n (n = 1, 2, 3,...) Times the field period of the imaging device,
The signal processor is
First and second computing units;
A determination unit for determining the state of the subject,
The above signal is acquired every n fields in field units, and the signal is output to the first and second arithmetic units, respectively.
The first calculation unit includes:
In the same region, a first time average of the signal level difference in the m (m = 1, 2, 3,...) Field and the (m + 2) field is obtained.
The second arithmetic unit is
In the same region, a second time average of the signal level difference in the (m + 1) th and (m + 3) th fields is obtained,
The determination unit is
The detection system according to claim 1, wherein a square sum of the first time average and the second time average is obtained, and the state of the subject is determined according to the value of the square sum. The imaging apparatus is
Frame accumulation, interlace scanning type,
The light source is
The luminance changes at 4n (n = 1, 2, 3,...) Times the frame period of the imaging device,
The signal processor is
First and second computing units;
A determination unit for determining the state of the subject,
The above signal is acquired every 2n fields in field units, and the signals are output to the first and second arithmetic units, respectively.
The first calculation unit includes:
In the same region, a first time average of the signal level difference in the m (m = 1, 2, 3,...) Field and the (m + 2) field is obtained.
The second arithmetic unit is
In the same region, a second time average of the signal level difference in the (m + 1) th and (m + 3) th fields is obtained,
The determination unit is
The detection system according to claim 1, wherein a square sum of the first time average and the second time average is obtained, and the state of the subject is determined according to the value of the square sum. The imaging apparatus is
Frame accumulation, non-interlaced scanning type,
The light source is
The luminance changes at 4n (n = 1, 2, 3,...) Times the frame period of the imaging device,
The signal processor is
First and second computing units;
A determination unit for determining the state of the subject,
The signal is acquired every n fields in units of frames, and the signals are output to the first and second arithmetic units, respectively.
The first calculation unit includes:
In the same region, find a first time average of the signal level difference in the m (m = 1, 2, 3,...) And (m + 2) frames,
The second arithmetic unit is
In the same region, a second time average of the signal level difference in the (m + 1) th and (m + 3) th frames is obtained,
The determination unit is
The detection system according to claim 1, wherein a square sum of the first time average and the second time average is obtained, and the state of the subject is determined according to the value of the square sum. A signal processing method of a detection system having a light source or an imaging device that images a subject irradiated with the light source,
A first step of changing the luminance of the light source at a predetermined cycle of a scanning plane cycle of the imaging device;
A second step of acquiring a signal from the imaging device every predetermined scanning plane period;
A third step of obtaining a time average of the signal level difference from the signal level difference of the signal between a plurality of different scanning planes;
A fourth step of performing a predetermined calculation based on the time average value;
A fifth step of detecting the state of the subject according to a value of a calculation result of the calculation;
A signal processing method for a detection system.

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