JP3187068B2 - Smear removal circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a smear removing circuit, and more particularly to a smear removing circuit capable of removing smear generated when a high-luminance object is imaged by an imager.

[0002]

2. Description of the Related Art An imager that photoelectrically converts incident light into an electric signal using an image pickup device such as a CCD is used in electronic devices in various fields such as video devices. It is frequently used in imaging devices that convert video signals. It is widely known that when an image of a high-brightness subject is taken by an electronic still camera, a video movie, or the like using this imager, an unsightly smear is generated. This is because the smear leaks into the exposure charge vertically transferred under the high brightness light, and after the high brightness signal is obtained, the smear leaks in the vertical direction (downward).
Occurs.

FIG. 7 is a block diagram of a smear removing circuit in a conventional CCD imager. A video signal photoelectrically converted by a CCD image sensor 81 is provided with an S / H (sample and hold) circuit 82 for sampling and holding the signal. The signal is supplied to an A / D conversion circuit 83 for A / D conversion into a digital signal. In this case, the CCD image sensor 8
1, an S / H circuit 82 and an A / D conversion circuit 83 are driven by a drive signal from a CCD drive circuit 84. The drive circuit 84 generates a signal between itself and a synchronization signal generator 85 that generates a synchronization signal. The exchange is performed.

The digital output from the A / D conversion circuit 83 is controlled by a memory controller 88 and supplied to and stored in a field memory 87 for storing one field of CCD output. The memory output output from the field memory 87 and the CCD output output from the A / D conversion circuit 83 are input to a subtractor 90 via a changeover switch 89, and a signal having no smear is output from the output terminal. Is done. An operation sequence such as exposure control and timing control by each of the above circuits is governed by the system controller 86.

The operation of the above-described conventional example will be described with reference to a timing chart shown in FIG.
The charge reading from the charge storage unit of the CD image sensor 81 to the vertical transfer circuit is performed, for example, in a “prohibited” and a “normal reading” in synchronization with the rising edge of the vertical synchronization signal shown in FIG. It is done alternately. Therefore, C
As shown in FIG. 8B, the CD output is a smear output of only a smear component in the “prohibited” section, and a video signal output in which the smear component is superimposed on the effective signal component in the “normal read” section. Each is transferred. Then, the CCD output shown in FIG.
Since the data is read out after being accumulated for the field, the memory output is delayed by one field from that of FIG.
The waveform is as shown in FIG.

Therefore, the switching signal applied from the system controller 86 to the control terminal of the changeover switch 89 is switched to "H" and "L" for each field as shown in FIG. Then, the final output from the subtractor 90 that takes the difference between the CCD output and the memory output is
As shown in FIG. 8 (E), between the time t1 and t2, the value obtained by subtracting the memory output from the CCD output is obtained, and between the time t3 and t4, the value becomes the value obtained by subtracting the CCD output from the memory output. Only the effective signal component obtained by removing the smear component from the video signal output in which the smear component is superimposed on the component is output.

FIG. 9 is an explanatory view of a CCD image sensor showing another conventional example. This sensor 110 has a first HCC.
D (horizontal transfer register) 131 and second HCCD 132
And two horizontal transfer registers, and the first HCC
The output of D131 is supplied to the non-inverting input terminal of the subtractor 135 via the first S / H circuit 133, and the output of the second HCCD 132 is supplied to the inverting input terminal of the subtractor 135 via the second S / H circuit 134. , Respectively. In the first HCCD 131, the photosensitive units 111, 121,... Of the first line in the charge storage unit, and the photosensitive units 1 of the third line
The signal charges accumulated in the photosensitive portions of the odd lines such as 13, 123,... Are transferred via the vertical transfer registers 120, 130,. Further, the second HCCD 132 has the photosensitive units 112 and 12 of even lines in the charge storage unit.
The signal charges stored in 2, 114, 124,... Are respectively transferred.

In the case of reading out the stored electric charges in the another conventional example having the above-mentioned configuration, the normal reading is performed on the photosensitive portion of the odd-numbered line, and the first HCCD 13 is read out.
The video signal output in which the smear component is superimposed on the effective charge component, ie, the effective charge component, is transferred to 1, but the photosensitive portion of the even-numbered line is stored in the vertical transfer registers 120, 130,. Only the smear component is transferred to the second HCCD 132. Therefore, subtracter 1
An effective signal component obtained by removing the smear component from the video signal output is obtained at an output terminal of the video signal 35.

[0009]

However, by alternately controlling the application and inhibition of the read pulse of the stored charge for each field, a video signal output and a smear output are obtained. The first conventional example, in which the smear signal component is removed by delaying and subtracting this memory output from the current video signal output, requires <1> field memory or a delay circuit for one field. Therefore, the circuit scale becomes large.

<2> Since the exposure timing is shifted by one field in this case between the memory output and the current video signal output, if the subject is moving, there is a one-field timing shift in the subtraction target. This causes a problem. Therefore, if an attempt is made to add a circuit for detecting the movement of the subject, the circuit scale will be further increased.

<3> Since effective information can be obtained only every other field, the amount of video information is reduced to half of the originally obtainable information amount.

The odd lines among the elements of the photosensitive section read out the electric charges to the vertical transfer register, and the effective signal components including the smear component are read out to the first HCCD. The even lines do not read out the electric charges. Second only smear component
In the above-mentioned another conventional example in which an effective signal from which a smear component has been removed by subtracting between the first and second horizontal transfer registers is obtained, << 1 >> a special image for the CCD imager Two lines of sensors, that is, horizontal transfer registers are required, and the number of vertical transfer stages is required for one frame (two fields).

<2> Since the photosensitive portion of the even-numbered line is used only for detecting the smear component, the amount of information obtained from the image sensor is reduced to a half of that originally obtained.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a smear removing circuit capable of removing smear with a small circuit configuration in an apparatus using an imager such as a CCD.

[0015]

SUMMARY OF THE INVENTION A smear removing circuit according to the present invention responds to an input signal (VC) to its own system, which is an output video signal of the system, corresponding to the input signal during a horizontal scanning period. A first feedback circuit system in a positive feedback circuit mode by positively feedbacking the delayed signal to obtain an output signal (VB);
In addition, a negative feedback circuit mode is obtained by negatively feedbacking a signal obtained by multiplying the output of the first feedback circuit by a predetermined coefficient with respect to the input video signal (VA) of the system to obtain the output video signal (VC). A second feedback circuit system is provided, and the second feedback circuit system is connected to a subsequent stage of the imager to obtain a signal from which the smear signal component related to the imager has been removed as the output video signal (VC). Further, a signal obtained by multiplying an output video signal of the system by a predetermined coefficient and input signal (VC) to the own system, which is obtained by applying a delay corresponding to a horizontal scanning period to the input signal, is a positive feedback. To obtain an output signal (VB) to form a first feedback circuit system of a positive feedback circuit mode, and to provide a negative feedback to the input video signal (VA) of the system via the first feedback circuit system. The above output video (VC) to obtain a second feedback circuit system in a negative feedback circuit mode, and by connecting the second feedback circuit system to the subsequent stage of the imager, the smear of the imager is obtained as the output video signal (VC). A signal from which a signal component has been removed is obtained. Further, in response to an input signal (VC) to the own system, which is an output video signal of the system, a horizontal scanning period is applied to the input signal.
The first signal of the positive feedback circuit mode is obtained by positively feeding back a signal multiplied by a delay and a coefficient corresponding to the above to obtain an output signal (VB).
A feedback circuit system and an input video signal (V
A) is subjected to negative feedback via the first feedback circuit system to obtain the output video signal (VC), thereby forming a second feedback circuit system in a negative feedback circuit mode, and using the second feedback circuit system as an imager. The output video signal is obtained by removing the smear signal component related to the imager by connecting to a subsequent stage. (Figure 1
Note that the signals (VA),
(VB) and (VC) are provided for convenience of understanding, and do not limit the present invention in any way.

[0016]

In this smear removing circuit, as shown in FIG.
A first feedback circuit system that positively feeds back the output VB of the line memory 4 to the input terminal of the adder 3 via one input terminal of the adder 3 to perform a delay corresponding to a horizontal scanning period corresponding to one horizontal scanning line. Then, the integrated value of each line up to one line before the video signal applied to the other input terminal of the adder 3 is calculated. This integrated value can be predicted to be proportional to the smear component in the input video signal, which is an imager output that is generated thereafter.

Therefore, by multiplying the integrated value, which is the output of the first feedback circuit system, by a predetermined coefficient 1 / K in the coefficient unit 5, it can be made equal to the smear signal in the input video signal VA.
Therefore, the output of the coefficient unit is applied to the inverting input terminal of the subtractor 2 and the output VC of the subtracter 2 is applied to the other input terminal of the adder 3 to form the negative feedback circuit. The smear signal can be removed from the input video signal VA, which is the imager output, applied to the non-inverting input terminal of the subtracter 2 by the two feedback circuit system.

In this case, the interpolating position of the coefficient unit 5 may be a broken-line circle position 200, or a function of multiplying the coefficient may be included in the line memory 4.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to an electronic still camera will be specifically described below. FIG. 2 is a block diagram of the electronic still camera. The aperture of the subject light transmitted through the photographing lens 11 is controlled by an aperture mechanism 12, and the imager 1
An image is formed on the light receiving surface 3. The video signal photoelectrically converted by the imager 13 is digitized by an A / D converter 15 via an S / H circuit 14. This digital signal is subjected to a smear removal circuit 1 comprising a subtractor 2, an adder 3, a line memory 4, and a coefficient unit 5 to remove a smear component, and a camera process signal processor 16 for performing normal camera signal processing.
, And is output as an analog video signal by the D / A converter 17.

The imager 13, S / H circuit 14, A
The drive signal from the CCD drive signal generation circuit 18 is supplied to the / D converter 15 and the line memory 4 of the smear removal circuit 1. Send and receive. The synchronizing signal generation circuit 19 outputs a synchronizing signal for video for controlling the video signal processing of the camera to the camera process signal processing unit 16.
And sends a memory clear pulse to the line memory 4 of the smear removal circuit 1 for clearing the memory contents of the circuit 4 on a field-by-field basis.

The operations of the electronic still camera, such as photometry and exposure control, are controlled by a system controller 20 that controls the operation sequence of the entire camera. That is, a command is sent to the aperture mechanism 12 to control the aperture. Further, the CCD drive signal generation circuit 18
To control the shutter operation. Further, the coefficient unit 5 of the smear removing circuit 1 is controlled to vary the coefficient 1 / K. In this case, the coefficient 1 / K is set by the changeover switch 21.
For example, the system controller 20 detects this in accordance with settings such as shutter priority and aperture priority, and varies the coefficient 1 / K.

Next, the smear removing circuit 1 will be described. Generally, smears occur in a camera using a CCD imager in the vertical direction when a high-luminance subject is imaged. When this is shown as a screen image on the monitor TV, the shape becomes like a thin white band drawn in the vertical direction of a high-luminance round subject. The reason for this is that when high-luminance light is irradiated, light leaks into the vertical transfer path underneath, and the amount of smear generated is the illuminance of high-luminance light and signal charge in the vertical transfer path under high-luminance light irradiation. Is proportional to the time it crosses.

Therefore, when high-intensity light is irradiated, if the charge amount photoelectrically converted by the light is integrated for each horizontal scanning line, it is expected that the smear amount will occur in proportion to the integrated value. it can. Therefore, this predicted value is calculated as CC
By subtracting from the D output, the smear component can be removed.

A smear removing circuit 1 removes a smear component from a video signal output from an imager and outputs a signal free of smear. It comprises an adder 3 for adding a signal delayed by one line, a line memory 4 to which the output of the adder is input, and a coefficient unit 5 for multiplying the output of the memory 4 by a predetermined coefficient 1 / K. ing.

The smear removing operation of this embodiment having the above-described configuration will be described with reference to FIGS. For the sake of simplicity, as shown in FIG. 3, it is assumed that the entire screen 41 is black, and a square area 42 located in the center of the screen 41 is white, that is, a high-luminance subject. Then, the following condition setting is performed.

[A] As the time t elapses, scanning is performed downward from the upper side of the screen. Before the scanning, it is assumed that a memory clear signal for clearing the line memory 4 is applied. [B] The horizontal scanning line scans the black area as L (0), L (1),..., L (n-1) as shown on the right side of FIG. Enter region 42.
Since this white area 42 corresponds to m horizontal scanning lines,
It continues to the L (n + m-1) th line. The black area is scanned again from the L (n + m) line.

[C] The signal output level is constant for both the black area and the white area, that is, a constant level, that is, 0 in the black area and a in the white area, the effective exposure amount per horizontal scanning line is a.
However, in the white area, the effective exposure amount, that is, the effective signal component a
Is superimposed on the smear component b, which increases as the time t elapses (per scanning line). The smear amount b is proportional to the effective exposure amount a.

[0028]

[D] Further, the coefficient 1 / K in the coefficient unit 5
Is set appropriately so that the relationship b = (1 / K) a (11) is maintained.

Now, the operation of the smear removing circuit 1 set as described above is described by comparing the CCD output, that is, the signal level applied to the non-inverting input terminal of the subtractor 2 with VA, and the output level of the subtracter 2 with VA. VC and the output level of the line memory 4 will be described with reference to FIG.

[1] In the horizontal scanning line L (0), the memory clear signal is applied to reset the line memory 4, and the CCD output is zero because the black area 41 is scanned. Therefore, the output level VC of the subtractor 2 becomes zero.

[2] In the horizontal scanning line L (1), since a black area is photographed, the CCD output becomes 0. Further, the memory output VB of the line memory 4 becomes zero because the memory output of itself and the output of the subtractor at the previous time, that is, at the time of the horizontal scanning line L (0) are both zero. Therefore, the subtractor output VC
Also becomes zero.

[3] The above-mentioned state corresponds to the horizontal scanning line L (n
When the L (n) line is reached, the white area 42 in FIG. 3 is imaged, so that the CCD output VA has a level a as shown by the CCD output 50 in FIG.

[4] Now, for simplicity, the change in the CCD output will be summarized here.
The effective exposure amount for the (n) line is a. L (n + 1)
In the line, the effective exposure amount is a because the same white area is scanned. However, when the L (n) line is scanned, the smear amount b due to passing under the high-luminance subject is added to a + b.

Similarly, in the L (n + 2) line, two lines, the L (n) line and the L (n + 1) line, pass under high-luminance light irradiation.
b, whereby the CCD output becomes a + 2b. In the L (n + 3) line, the CCD output is a
+ 3b, and similarly, at the L (n + m-1) th line, the CCD output becomes a + (m-1) b.

At the L (n + m) -th line, FIG.
Return to the black area, the effective exposure amount becomes 0,
The smear amount mb resulting from passing under m high-luminance light irradiation of m lines before the L (n + m) line is obtained as a CCD output. This means that the following L (n + m + 1), L
(N + m + 2),...

[5] Returning again to the L (n + 1) line, the memory output VB and the subtractor output VC are converted to the CCD output V
A description will be given step by step while relating to A. The L (n
-1) Since the CCD output is zero up to the line, the memory output V
The points at which B and the subtractor output VC also become zero are as described above. When the L (n) line is reached, the CCD output 50 becomes a, so the subtractor output 52 also becomes a. However, the memory output 51 is either the CCD output VA or the subtractor output VC in the preceding L (n-1) line. Is also zero, so it becomes zero.

The memory output 54 on the L (n + 1) line becomes a because it is the sum of the memory output 51 and the subtractor output 52 on the L (n) line one line before. The memory output 54 is multiplied by 1 / K in the coefficient unit 5 of the smear reduction circuit 1 in FIG. 2 to become (1 / K) a, and is applied to the inverting input terminal of the subtractor 2. Since the voltage (1 / K) a applied to the inverting input terminal is related as b = (1 / K) a in the above equation (11),
Of the CCD output 53 applied to the non-inverting input terminal of
If it is less than + b, the subtractor output 55 becomes a with the smear component canceled.

[6] In the L (n + 2) line, the CCD output 56 becomes a + 2b as described in the above [4]. On the other hand, the memory output 57 is the sum of its own signal 54 one line before and the subtractor output 55, so 2a is output. Since the memory output 57 of the value 2a is multiplied by 1 / K in the coefficient unit 5, it becomes 2b by applying the relationship of the above-mentioned equation (11) to this. Therefore, the output 58 of the subtractor is only the effective exposure amount a from which the smear component has been canceled.

[7] For the L (n + 3) line, the memory output 60 is the memory output 57 of the previous line and the subtractor output 58
And 3a. Therefore, the value (1 / K) × 3a obtained by multiplying the memory output 60 by 1 / K by the coefficient unit 5 is calculated by the subtractor 2
If subtracted from a + 3b of the CCD output 59, the subtractor output 61 will be only the exposure amount a from which the smear component has been canceled.

[8] Similarly, the CCD output becomes a
+ 4b, a + 5b,... But the memory output is also 4a, 5
a,..., the smear component is canceled from the output of the subtracter, and the output of the effective exposure amount a is obtained. And L
At the (n + m-1) line, the CCD output 62 becomes a
+ (M−1) b, but the memory output 63 becomes (m−
1) Since a is obtained, the output of the coefficient unit (m-1) b obtained by multiplying this by 1 / K by the coefficient unit 5 is subtracted from the CCD output 62 by the subtractor 2 to cancel the smear component. The a of the subtractor output 64 is obtained.

[9] When the L (n + m) line is reached, CC
The D output 65 is only the smear component mb. On the other hand, the memory output 66 includes the memory output 63 of the previous line and the subtractor output 6
4 and ma, which is calculated by the coefficient unit 5 as (1 /
(K) times (1 / K) × ma = mb. Accordingly, the smear component of the subtractor output 67 is canceled, and zero corresponding to the black area 41 in FIG. 3 is output.

[10] After the L (n + m + 1) line, a zero output corresponding to the black area 41 is obtained as in the case of the L (n + m) line.

The relationship of FIG. 4 will be described with reference to the diagram of FIG. 5. The CCD output VA, the memory output VB, and the subtractor output VC
Means solid lines LR1, LR2 and LR3 between the line L (n) and the line L (n + m-1) with respect to the time t on the horizontal axis.

That is, the CCD output VA changes from the L (n) line to the L (n + m-1) line by the broken line L.
Effective exposure amount component area 71a having a constant amplitude a indicated by D1
And the smear amount b component region 71b, which increases in accordance with the number of passing lines after passing under high-luminance light irradiation.

The memory output VB is a solid line LR2 between the line L (n) and the line L (n + m-1).
Are output as shown by the following expression, but are compressed as shown by the broken line LD2 by multiplying by 1 / K in the coefficient unit 5. If the inclination of the broken line LD2 is made equal to the inclination of the solid line LR1 based on the smear amount component of the smear output of the CCD output, the effective exposure amount obtained by canceling the smear component as shown by the solid line LR3 is output as the subtractor output VC. Only component a will be obtained.

In FIGS. 3 to 5, all the lines up to the L (n-1) line are black regions, and the lines from the L (n) line to the horizontal scanning line m.
Although the description has been given assuming that the white area is within the range of the book, since the white level is usually different for each pixel in an actual subject, the operation of the smear removal circuit according to the present invention in such a general case is expressed by a mathematical formula. This will be described below.

Assuming that the CCD output on an arbitrary horizontal scanning line L (n) is A (n), the effective signal component contained in A (n) is a (n), and the smear component is b (n).
Then, the smear component generated in the L (n) line is proportional to the number of lines transferred under the high-luminance light irradiation up to the L (n-1) line immediately before the L (n) line. I do. That is,

[0049]

Becomes Here, K1 is a constant determined by the smear characteristic of the imager.

[0051]

The relationship is as follows. Therefore, the CCD output A (n) on the L (n) line is given by the following equation.

[0053]

Next, assuming that the output of the subtractor is C (n) and the output of the memory is B (n), C (n) = A (n)-(1 / K2) B (n) (2) become. Here, the coefficient K2 is a coefficient of the coefficient unit 5 to be multiplied by the memory output, and is indicated by K in FIG. On the other hand, the memory output B (n) is equal to the sum of the subtractor output up to the previous line, that is, the sum of the subtractor output to the own memory output of the previous line.

[0055]

Is obtained. Therefore, by substituting the above equation (3) into the equation (2),

[0057]

Is obtained. Therefore, if (1) is substituted into the above equation (4),

[0059]

Is obtained. Here, the subtractor output C (n) becomes an effective signal component a (n), that is, a smear component b (n).
In order to remove the signal and make only the effective signal component a (n), C (n) = a (n) may be satisfied. Since this is also ΣC (n−1) = Σa (n−1), The above equation (5) becomes 1 / K1 = 1 / K2. As a result, if K1 = K2 = K, only the effective signal component from which the smear component has been removed is obtained in the subtractor output C (n).

As described in detail in the above embodiment, the present invention is based on the assumption that the smear prediction value is proportional to the integrated value of the electric charge photoelectrically converted from the high-intensity light in units of horizontal scanning lines. Is subtracted from the CCD output to remove the smear. Therefore, a problem arises when the proportionality constant in the above proportional relationship changes depending on the exposure condition of the camera. This will be described below with reference to FIGS.

As is well known, for the exposure control in the camera, as shown in Table 1 below, both the aperture and the shutter speed are fixed, and a fixed type in which shooting is performed using the depth of field of the lens, and a fixed aperture In addition, there are an aperture priority that varies the shutter speed, a shutter priority that varies the aperture while fixing the shutter speed, and a program AE (automatic exposure control) that varies both the aperture and the shutter speed.

[0063]

[Table 1]

The setting of exposure conditions in each of these control methods is performed by the system controller 20 by operating the changeover switch 21 in FIG.

First, as shown in FIG. 6A, when the aperture value is F4 and the electronic shutter speed is 1/500 second,
Assume that the ratio between the effective exposure signal component and the smear component was 4: 1. Therefore, the system controller 20 instructs the coefficient unit 5 to calculate the coefficient 1 / K to be multiplied by the memory output as 1 / K.
Set to 4.

<A> FIG. 6 in which the shutter speed is reduced from 1/500 to 1/1000 second while the aperture value is kept at F4
Consider the case (B). In this case, the effective exposure signal component in the CCD output is halved because the exposure time is halved, but the smear component is divided by the number of lines on the transfer path corresponding to the intensity of the light hitting the imager. 6A, which is different from the case of FIG. 6A because the aperture value is the same regardless of the shutter speed. That is, since the ratio between the effective exposure signal component and the smear component in the CCD output becomes 2: 1, it is necessary to change the coefficient 1 / K in the coefficient unit 5 from ４ to １ ／. This corresponds to the aperture priority of Category 3 in Table 1 above.

<B> The shutter speed is set as shown in FIG.
6 (C) in which the aperture value is increased by one step from F4 to F2.8 while keeping the same 1/500 second as in (A). In this case, the effective exposure signal component in the CCD output is doubled because the aperture is opened by one stage, but the smear component is also doubled because it is proportional to the amount of light. Therefore, since the ratio between the effective exposure signal component and the smear component in the CCD output remains unchanged at 4: 1, there is no need to change the coefficient 1 / K. This corresponds to the shutter priority of Category 2 in Table 1 above.

<C> Consider the case of FIG. 6D in which the aperture value is set from F4 to F2.8 and the shutter speed is set from 1/500 seconds to 1/250 seconds. In this case, the effective exposure signal component in the CCD output doubles when the aperture value changes, and doubles when the shutter speed changes. On the other hand, the smear component only doubles with a change in the aperture value regardless of a change in the shutter speed. Therefore, since the ratio of the effective exposure signal component to the smear signal component in the CCD output becomes 8: 1, it is necessary to change the coefficient 1 / K from 1/4 in FIG. 6A to 1/8. This corresponds to the program AE of the section 4 in Table 1 above.

The shutter according to the present invention includes an element shutter that controls the charge accumulation time in the imager and a mechanical shutter that varies the exposure time by using a mechanical shutter member.

By the way, the system controller 20
Since the aperture control is performed by issuing an aperture control command to the aperture mechanism 12, the aperture value information is naturally stored in the internal memory means. Further, since an electronic shutter control command is issued to the CCD drive signal generation circuit 18, information on the shutter speed is also stored. Therefore, when the exposure conditions are changed as described above, the controller 20 refers to a built-in lookup table, and based on the information on the exposure control, the coefficient unit 5 of the smear removal circuit 1.
Will be changed.

In the above embodiment, the A / D converter 15
Although the smear component is removed after the signal is changed to a digital signal in FIG. 2 (see FIG. 2), it goes without saying that the processing may be performed with the analog signal as it is.

Further, the insertion point of the coefficient unit 5 in the smear removal circuit 1 according to the present invention may be provided at the position shown by the broken circle 200 in FIG. 1 from the position shown in FIGS. It is described in item 2. The reason for this is that the present invention calculates the smear component generated when the signal charge crosses the vertical transfer path under the irradiation of the high-intensity light. This is because, after integration by the integrating means comprising the line memory 4, 1 / K by the coefficient unit 5 or 1 / K by the coefficient unit 5 and then integration by the integrating means are the same.

Further, the coefficient unit 5 may be removed, and this function may be provided to the line memory 4, which will be described in claim 3. As a means for this, a bit shift, which is usually used in a digital multiplication / division circuit, can be considered. That is, if the full bits of the line memory 4 are k bits, a bit shift of the k bits results in an output of 1 / K of the memory output. According to the above-described embodiment, << 1 >> the size can be significantly reduced as compared with the conventional smear removing means.

<2> Since processing can be performed in real time, it is possible to deal with a moving subject.

<3> An ordinary amount of information can be obtained without reducing the amount of information obtained from the imager.

<< 4 >> It is not necessary to use a special imager, and a commonly used type such as an interline type, a frame transfer type, or a frame interline type can be used as it is.

Although the above embodiment has been described with reference to an example in which the present invention is applied to an electronic still camera, the present invention is not limited to this, but is applicable to all video cameras using a CCD or the like. Needless to say.

[0078]

As described above, according to the present invention, the output video signal of the system, that is, the input signal to the own system,
A signal obtained by applying a predetermined delay to the input signal is positively fed back to obtain an output signal, thereby forming a first feedback circuit system of a positive feedback circuit mode, and the first feedback circuit for an input video signal of the system. A negative feedback circuit obtains the output video signal by negatively feedbacking a signal obtained by multiplying the output of the second circuit by a predetermined coefficient.
A remarkable effect of removing a smear signal component related to the imager from the output video signal with a simple circuit configuration in which a feedback circuit system is used and only these two feedback circuit systems are connected to the subsequent stage of the imager is exhibited.

[Brief description of the drawings]

FIG. 1 is a block diagram of a smear removing circuit according to an embodiment of the present invention.

FIG. 2 is a block diagram of an electronic still camera to which the present invention is applied.

FIG. 3 is a diagram showing a shooting target screen for explaining the operation of the embodiment.

FIG. 4 is a diagram showing signal levels of respective units in the embodiment.

FIG. 5 is a signal waveform diagram of each section in the present embodiment.

FIG. 6 is a view for explaining changes in exposure conditions in the embodiment.

FIG. 7 is a block diagram of a conventional electronic still camera that performs smear removal.

FIG. 8 is a timing chart of the operation of each section in FIG. 7;

FIG. 9 is a diagram illustrating smear removal in another conventional example.

[Explanation of symbols]

 13 ... Imager

Claims (3)

(57) [Claims] An output signal is obtained by positively feeding back a signal obtained by delaying an input signal to the own system, which is an output video signal of the system , corresponding to the horizontal scanning period. In this manner, a first feedback circuit system of a positive feedback circuit mode is provided, and a signal obtained by multiplying an output of the first feedback circuit by a predetermined coefficient with respect to an input video signal of the system is negatively fed back to the output video signal. A signal obtained by removing the smear signal component related to the imager as the output video signal by connecting the second feedback circuit system to a subsequent stage of the imager so as to obtain a signal and forming the second feedback circuit in a negative feedback circuit mode. And a smear removing circuit characterized by: 2. A method in which a signal obtained by multiplying an output video signal of the system by a predetermined coefficient and calculated by multiplying the input signal to the own system by subjecting the input signal to a delay corresponding to a horizontal scanning period is positively feedback. A first feedback circuit system of a positive feedback circuit mode is provided so as to obtain an output signal, and negative feedback is applied to the input video signal of the system via the first feedback circuit system, and the output video signal is A second feedback circuit system in a negative feedback circuit mode is obtained as described above. By connecting the second feedback circuit system to the subsequent stage of the imager, a signal from which the smear signal component relating to the imager has been removed is obtained as the output video signal. A smear removing circuit characterized in that: 3. A signal obtained by multiplying a signal obtained by multiplying a delay and a coefficient corresponding to a horizontal scanning period to an input signal to the own system, which is an output video signal of the system, by applying positive feedback to the output signal. To obtain the output video signal by applying a negative feedback to the input video signal of the system via the first feedback circuit system so as to obtain the output video signal. A second feedback circuit system of a negative feedback circuit mode, wherein the second feedback circuit system is connected to a subsequent stage of the imager to obtain a signal from which the smear signal component related to the imager has been removed as the output video signal. A smear removal circuit.