JP4932460B2 - Smear correction method and smear correction unit - Google Patents

Description

  The present invention relates to a smear correction method and a smear correction unit.

  Conventionally, a charge transfer type imaging device (CCD (Charge Coupled Device)) has been widely known as one of solid-state imaging devices.

  If a CCD is used, a good quality image can be acquired. Therefore, CCD is used in a wide range of products. However, due to the characteristics of the CCD, there is a problem that smear occurs when light having a predetermined intensity or more enters the imaging region of the CCD. Note that this phenomenon is particularly problematic in a camera for a portable terminal in which so-called electronic shutter technology is used.

  Japanese Patent Application Laid-Open No. 2004-133620 discloses a technique for suppressing an image signal from being excessively corrected by a correction signal generated based on a smear signal, as a countermeasure against CCD smear.

FIG. 14 is a schematic configuration diagram of a smear correction circuit described in Patent Document 1. As shown in FIG. 14, the smear correction circuit 500 includes a selection circuit 501, a subtraction circuit 502, an integration circuit 503, a line memory 504, a gain controller 505, a median filter 506, and a low-pass filter 507. The function of each element is as described in Patent Document 1. In the smear correction circuit shown in FIG. 14, the smear signal passes through the low-pass filter and is given to the subtraction circuit 502.
JP 2005-159564 A

  The smear signal is a signal from which high frequency components have been removed and noise has been removed by passing through a low-pass filter. However, the signal component of the smear signal may be excessively removed by passing through the low-pass filter.

  With reference to FIG. 15, the problem that the signal component of the smear signal is excessively removed by the low-pass filter will be described. In FIG. 15, the horizontal distribution of the true smear signal is indicated by a broken line. Further, the horizontal distribution of the signal (correction signal) after the true smear signal passes through the low-pass filter is indicated by a solid line.

  As indicated by the arrows in FIG. 15, the level of the correction signal deviates from the level of the true smear signal at a point where the change in the signal level in the horizontal distribution of the true smear signal is acute. Even if the smear component of the image signal is removed using the correction signal deviating from the level of the true smear signal, the smear component of the image signal cannot be accurately removed. In the conventional smear correction technique, the signal component itself of the smear signal may be excessively removed by the low-pass filter, and the smear correction cannot be performed with high accuracy.

  The smear correction method in the charge transfer type imaging device according to the present invention acquires a smear signal output from each of a plurality of readout lines, and the smear signal output from the readout line for each of the plurality of readout lines. And a correction signal is determined based on a signal having a frequency component equal to or lower than a predetermined frequency of the smear signal output from the readout line, and a smear of the image signal output from the readout line is determined using the determined correction signal. Remove ingredients.

  The smear correction method in the charge transfer type imaging apparatus according to the present invention acquires a smear signal output from the first readout line, acquires a smear signal output from the second readout line, and outputs the smear signal output from the first readout line. A first mixed signal in which the smear signal output or the smear signal output from the first read line and a signal having a frequency component equal to or lower than a predetermined frequency of the smear signal output from the first read line are mixed. A first correction signal is determined based on the signal, a smear component of the image signal output from the first readout line is removed using the determined first correction signal, and the first correction signal is output from the second readout line. The smear signal having a frequency component equal to or lower than a predetermined frequency, or the smear signal output from the second readout line and the smear signal output from the second readout line. A second correction signal is determined based on a second mixed signal in which a signal having a frequency component equal to or lower than a predetermined frequency of the mean signal is mixed, and is output from the second readout line using the determined second correction signal. The smear component of the processed image signal is removed.

The smear correction unit in the charge transfer type imaging device according to the present invention uses the correction signal generated based on the smear signal output from the charge transfer type imaging device, and outputs the image signal output from the imaging device. Based on a calculation unit that removes smear components, a selection unit that selects the smear signal output from the imaging device, and the selected smear signal and a signal having a frequency component equal to or lower than a predetermined frequency of the selected smear signal. A correction signal generating unit that generates the correction signal and outputs the correction signal to the arithmetic unit.
When the level of the selected smear signal is higher than the first threshold, the correction signal generation unit outputs the selected smear signal as the correction signal to the arithmetic unit, and the selected smear signal When the level is lower than the first threshold, the signal having a frequency component equal to or lower than a predetermined frequency may be output to the arithmetic unit as the correction signal.
Alternatively, the correction signal generation unit is a hybrid signal in which the selected smear signal and the signal having a frequency component equal to or lower than a predetermined frequency are mixed based on a difference value between the smear signals output from adjacent readout lines. The hybrid ratio is adjusted, and the hybrid signal with the hybrid ratio adjusted is output as the correction signal to the arithmetic unit.

  The smear correction method in the charge transfer type imaging device according to the present invention acquires a smear signal output from each of a plurality of readout lines, and the smear signal output from the readout line for each of the plurality of readout lines. Based on the level of the smear signal, a correction signal is determined by controlling a ratio of a signal having a frequency component equal to or higher than a predetermined frequency of the smear signal, and the image signal output from the readout line using the determined correction signal is determined. Remove smear components.

  A smear correction method in a charge transfer type imaging device according to the present invention acquires a smear signal output from each of a plurality of readout lines, and based on a difference value between the smear signals output from adjacent readout lines. The correction signal is determined by controlling the ratio of the signal having a frequency component equal to or higher than the predetermined frequency of the smear signal, and the smear component of the image signal output from the readout line is removed using the determined correction signal. .

  According to the present invention, smear correction can be performed with high accuracy.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, each embodiment is simplified compared with the structure which can be employ | adopted with an actual product for convenience of explanation. Since the drawings are simple, the technical scope of the present invention should not be interpreted narrowly based on the drawings. The drawings are only for explaining the technical matters, and do not reflect the exact sizes or the like of the elements shown in the drawings. The same elements are denoted by the same reference numerals, and redundant description is omitted.

[First Embodiment]
First, a configuration of a charge transfer type imaging device (CCD (Charge Coupled Device) will be described. Here, an interline transfer type CCD will be described, but other types (for example, a frame transfer type, a frame Interline transfer system, etc.) may be used.

  FIG. 1 shows a schematic configuration diagram of the CCD 1. As shown in FIG. 1, the CCD 1 includes a plurality of vertical transfer lines VL1 to VL12, a horizontal transfer line HL, and a plurality of pixels (pixels) Px. In the interline transfer type CCD, the vertical transfer line VL corresponds to a readout line.

  As shown in FIG. 1, the imaging area of the CCD is divided into an OB (Optical Black) area and an Image area. The OB area is set to an area of two lines (ab lines). The Image area is set to an area of 5 lines (c to g lines).

  On the OB region, for example, a light shielding film such as aluminum (Al) is deposited. Therefore, the detected light is not directly incident on the pixels in the OB region. The smear signal is output from the CCD 1 as charges are read from the pixels in the OB area. The smear signal output from the CCD 1 is input to a subsequent processing circuit.

  The Image area is a so-called imaging area. Therefore, the light shielding film is not deposited on the image area unlike the OB area. The image signal is output from the CCD 1 as charges are read from the pixels in the image area. The image signal output from the CCD 1 is input to a subsequent processing circuit.

  In the following description, the smear signal that is output when the pixel a1 in the OB area is read may be simply identified as a1 according to the address of the pixel. The same applies to other pixels in the OB area. In addition, the image signal output when the pixel c1 in the image area is read may be simply identified as c1 in accordance with the pixel address. The same applies to other pixels in the image area.

  Each of the vertical transfer lines VL1 to VL12 uses a bucket relay system to transfer charges accumulated in each pixel in the order of a row to g row based on a timing signal from a shift register (not shown). Forward to.

  The horizontal transfer line HL transfers the charges sequentially transferred from the vertical transfer lines VL1 to VL12 to the subsequent reading circuit. The charge transferred from the horizontal transfer line HL is converted into a voltage signal by drain diffusion. Then, it is converted into a digital signal by a subsequent processing circuit.

  Here, FIG. 2 shows a configuration diagram of the smear correction unit A according to the first embodiment. The smear correction unit A removes the smear component of the image signal output from the CCD 1 and outputs the image signal from which the smear component has been removed. As shown in FIG. 2, the smear correction unit 10A includes a selection unit 11, a subtraction unit (calculation unit) 12, a smear signal processing unit 13, a correction signal generation unit 16, and a timing control unit 20. The input terminal Pin receives a signal that is output from the CCD 1 and converted into a digital signal. More specifically, the input terminal Pin receives a smear signal read along with charge readout from the pixels in the OB region and an image signal read out along with charge readout from the pixels in the Image region.

  The image signal and smear signal output from the input terminal Pin are input to the selection unit 11. The image signal is directly output from the selection unit 11 and input to the subtraction unit 12. On the other hand, the smear signal is output from the selection unit 11 to the smear signal processing unit 13. As will be described later, the smear signal processing unit 13 outputs an average smear signal. The average smear signal is input to the correction signal generator 16. Based on the level of the average smear signal output from the smear signal processing unit 13, the correction signal generation unit 16 generates an NLP signal (a signal not subjected to a low-pass filter) or an LP signal (a signal subjected to a low-pass filter). Either one is output to the subtraction unit 12 as a correction signal. The subtraction unit 12 uses the correction signal output from the correction signal generation unit 16 to remove the smear component of the image signal.

  This will be described in more detail below.

The selection unit 11 selects an output path of the input signal based on the control signal CS1 from the timing control unit 20.
Note that the timing control unit 20 outputs a low-level control signal CS1 during a smear signal reading period (a period in which a smear signal is read from the CCD 1). On the other hand, in the image signal reading period (period in which an image signal is read from the CCD 1), the timing control unit 20 outputs a high-level control signal CS1. Therefore, when the low-level control signal CS1 is input from the timing control unit 20 (during the smear signal reading period), the selection unit 11 outputs a smear signal to the smear signal processing unit 13. When the high-level control signal CS <b> 1 is input from the timing control unit 20 (in the image signal reading period), the selection unit 11 outputs the image signal to the subtraction unit 12.

  The smear signal processing unit 13 includes a smear signal calculation unit 14 and a smear signal storage unit 15. The smear signal calculation unit 14 integrates the smear signal, and divides the integrated value by the number of integrated smear signals. That is, the smear signal processing unit 13 averages the smear signal. The smear signal storage unit 15 stores the averaged smear signal (average smear signal). In other words, the smear signal storage unit 15 stores the average smear signal in the storage area.

  The smear signal processing unit 13 performs a storage operation or an output operation based on the control signal CS1 from the timing control unit 20. When the low-level control signal CS1 is given from the timing control unit 20 (in the smear signal reading period), the smear signal processing unit 13 performs a storage operation. Specifically, the smear signal processing unit 13 averages the smear signal by the smear signal calculation unit 14 and stores the average smear signal by the smear signal storage unit 15 as described later. When the high-level control signal CS1 is given from the timing control unit 20 (in the image signal readout period), the smear signal processing unit 13 performs an output operation. Specifically, the smear signal processing unit 13 outputs the average smear signal stored in the smear signal storage unit 15 to the correction signal generation unit 16.

  The smear signal calculation unit 14 and the smear signal storage unit 15 are configured to be able to communicate with each other. Therefore, the smear signal storage unit 15 may be used not only for holding the calculation result of the smear signal calculation unit 14 but also in the calculation process by the smear signal calculation unit 14.

  Here, the storage operation of the smear signal processing unit 13 will be described with reference to FIG. As shown in FIG. 1, in the present embodiment, the OB area is set to an area for two lines (a line and b line). The smear signal processing unit 13 averages and stores two smear signals for each of the vertical transfer lines VL1 to VL12. That is, the smear signal processing unit 13 integrates two smear signals, divides the integrated value by 2, and stores the calculation result.

  As shown in FIG. 3, first, smear signals a1 to a12 (the smear signal a1 is a signal obtained by reading out charges from the pixel a1. The same applies to a2 to a12) are input to the smear signal processing unit 13 (FIG. 3). 3 (1)). Next, smear signals b1 to b12 (the smear signal b1 is a signal obtained by reading out charges from the pixel b1. The same applies to b2 to b12) are input to the smear signal processing unit 13 (see FIG. 3B). ). The smear signal calculation unit 14 integrates each of the smear signals when the smear signals to be averaged are prepared for each of the plurality of vertical transfer lines VL1 to VL12 (see FIG. 3 (3)). Next, the smear signal calculation unit 14 divides the integrated value by the number of integrated smear signals 2, and obtains an average smear signal (see FIG. 3 (4)). The smear signal storage unit 15 stores the average smear signal obtained in this way. The smear signal storage unit 15 has storage areas corresponding to the vertical transfer lines VL1 to VL12.

  When the smear signal processing unit 13 performs an output operation, the average smear signal stored in the storage area of the smear signal storage unit 15 is output from the smear signal processing unit 13 to the correction signal generation unit 16 in the stored order. . In addition, the reliability of smear correction can be enhanced by averaging the smear signal for each of the vertical transfer lines VL1 to VL12.

  The correction signal generator 16 has paths P1, P2 and a path P3. The correction signal generation unit 16 includes a low-pass filter unit 17, a determination unit 18, and a selection unit 19. Based on the determination result by the determination unit 18, the correction signal generation unit 16 applies a low-pass filter to the average smear signal (hereinafter referred to as an LP signal) or a signal that does not apply a low-pass filter to the average smear signal (hereinafter referred to as NLP). Signal) is determined as a correction signal, and this correction signal is output to the subtraction unit 12.

  The average smear signal input from the smear signal processing unit 13 is branched into three paths P1 to P3 by the node N1 and the node N2. The average smear signal is directly input to the selection unit 19 via the path P1. Further, a high frequency component (a signal component having a predetermined wavelength or more) is filtered by the low pass filter unit 17 through the path P <b> 2 and input to the selection unit 19.

  The average smear signal is input to the determination unit 18 via the path P3. The determination unit 18 determines whether the level of the average smear signal is higher or lower than the threshold value Ref1 (first threshold value). When the level of the input smear signal is higher than the threshold value Ref1, the determination unit 18 outputs a high level control signal CS2. This instructs the selection unit 19 to select the route P1 as the input route. When the level of the input smear signal is lower than the threshold value Ref1, the determination unit 18 outputs a low level control signal CS2. Thus, the selection unit 19 is instructed to select the route P2 as the input route.

  When the high-level control signal CS2 is output from the determination unit 18, the selection unit 19 selects the path P1 as an input path, and outputs the average smear signal (NLP signal) as it is to the subtraction unit 12 as a correction signal. When the low-level control signal CS2 is output from the determination unit 18, the selection unit 19 selects the path P2 as an input path, and uses a signal (LP signal) having a frequency component equal to or lower than a predetermined frequency of the average smear signal as a correction signal. , Output to the subtracting unit 12.

  As described above, the NLP signal input from the smear signal processing unit 13 to the selection unit 19 via the path P1 is the average smear signal itself stored in the smear signal processing unit 13. Since the NLP signal is an average smear signal that has not been subjected to a low-pass filter, the NLP signal includes noise components such as noise during charge-voltage conversion from the CCD 1.

  The LP signal input from the smear signal processing unit 13 to the selection unit 19 via the path P2 is an average smear signal subjected to a low-pass filter. In other words, the high-frequency component of the average smear signal is a filtered signal. That is, the average smear signal is a signal having a frequency component equal to or lower than a predetermined frequency. By applying a low-pass filter, the LP signal is filtered with noise components such as noise at the time of charge-voltage conversion from the CCD 1.

  The subtraction unit 12 uses the correction signal output from the correction signal generation unit 16 to remove the smear component of the image signal input from the selection unit 11. The subtraction unit 12 removes a smear component of the image signal output from the vertical transfer line using the NLP signal or the LP signal based on the smear signal output from the vertical transfer line for each of the vertical transfer lines VL1 to VL12. . For example, the subtracting unit 12 uses the NLP signal or the LP signal based on the smear signal output from the vertical transfer line VL1 to remove smear components of the image signals 1c to 1g output from the vertical transfer line VL1.

  As is clear from the above description, in the present embodiment, when the average smear signal is higher than the threshold value Ref1, the NLP signal is used as the correction signal. Thereby, it is suppressed that the signal component of a smear signal is removed excessively like the past. The correction signal supplied to the subtracting unit 12 is closer to a true smear signal. As a result, the image signal output from the subtracting unit 12 is preferably obtained by removing the smear component. On the other hand, when the average smear signal is lower than the threshold value Ref1, the LP signal is used as the correction signal. The LP signal is a signal from which the noise component of the average smear signal has been removed. Therefore, the image signal output from the subtracting unit 12 is preferably obtained by removing the smear component.

  With reference to FIG. 4, the contribution of this embodiment to the prior art will be described. As shown in FIG. 4, the horizontal distribution of the true smear signal is indicated by a broken line. The horizontal distribution of the correction signal output from the correction signal generator 16 is indicated by a solid line. In this example, the smear signal level = 20 is set as the threshold value.

  In Range1 and Range2, the correction signal input to the subtraction unit 12 is an NLP signal. In other areas, the correction signal input to the subtraction unit 12 is an LP signal. As shown in FIG. 4, the correction signal particularly indicated by the arrow is faithful to the true smear signal level. In other words, since the average smear signal (NLP signal) from which the high-frequency component is not removed is used as the correction signal at the portion where the smear signal level changes sharply, the signal component of the smear signal is excessively removed by the low-pass filter. There is no. Thus, a signal that has been selectively subjected to a low-pass filter is used (an LP signal that has undergone a low-pass filter is used as a correction signal when desired, and an NLP signal that is not subjected to a low-pass filter is used as a correction signal when not desired) Thus, the smear component of the image signal can be effectively removed.

  Finally, the operation of the smear correction unit 10A will be described using the timing chart of FIG. From time t1 to time t3 is a smear signal readout period, and after time t3 is an image signal readout period. Between time t1 and time t2, a smear signal in the a-th row of the CCD 1 is output from the CCD 1 and input to the input terminal Pin. Between times t2 and t3, a smear signal in the b-th row of the CCD 1 is output from the CCD 1 and input to the input terminal Pin. Between time t3 and time t4, the image signal in the c-th row of the CCD 1 is output from the CCD 1 and input to the input terminal Pin. From time t4 to time t5, the image signal of the d-th row of the CCD 1 is output from the CCD 1 and input to the input terminal Pin. For simplification of description, description of subsequent lines is omitted. In the present embodiment, it is assumed that the smear signal exceeds the threshold value Ref1 in the vertical transfer lines VL2, 4, 5, 6, 8, 11, and 12.

  Between times t1 and t2, the timing controller 20 outputs a low level control signal CS1. The selection unit 11 outputs the input smear signal to the smear signal processing unit 13 based on the low level control signal CS1. The smear signal processing unit 13 performs the above-described storage operation based on the low-level control signal CS1. The operation between time t2 and t3 is similar to the operation between time t1 and t2.

  Between time t3 and time t4, the timing control unit 20 outputs a high-level control signal CS1. The selection unit 11 sequentially outputs the input c-th row image signal to the subtraction unit 12 based on the high-level control signal CS1. The smear signal processing unit 13 performs the above-described output operation based on the high-level control signal CS1.

  As described above, the level of the smear signal is higher than the threshold value Ref1 in the vertical transfer lines VL2, 4, 5, 6, 8, 11, and 12. During times t3 to t4, the subtraction unit 12 uses an average smear signal (NLP signal) of smear signals output from each vertical transfer line VL2, 4, 5, 6, 8, 11, 12 as a correction signal. Thus, the smear component of the image signal output from each vertical transfer line VL2, 4, 5, 6, 8, 11, 12 is removed. Specifically, the subtracting unit 12 subtracts the average smear signal (NLP signal) of the smear signal output from the vertical transfer line VL2 from the image signal output from the vertical transfer line VL2. The subtracting unit 12 subtracts the average smear signal (NLP signal) of the smear signal output from the vertical transfer line VL4 from the image signal output from the vertical transfer line VL4.

  On the contrary, the level of the smear signal is lower than the threshold value Ref1 in the vertical transfer lines VL1, 3, 7, 9, and 10. During time t3 to t4, the subtracting unit 12 uses a signal (LP signal) obtained by filtering the high-frequency component of the average smear signal of the smear signal output from each vertical transfer line VL1, 3, 7, 9, 10 as a correction signal. ) To remove smear components of the image signals output from the vertical transfer lines VL1, 3, 7, 9, and 10. Specifically, the subtracting unit 12 subtracts a signal (LP signal) obtained by filtering the high-frequency component of the smear signal output from the vertical transfer line VL1 from the image signal output from the vertical transfer line VL1. The subtracting unit 12 subtracts a signal (LP signal) obtained by filtering the high-frequency component of the average smear signal of the smear signal output from the vertical transfer line VL3 from the image signal output from the vertical transfer line VL3.

  The operation between time t4 and t5 is the same as the operation between time t3 and t4.

  In this embodiment, when the level of the average smear signal is higher than the threshold value Ref, an NLP signal is used as the correction signal. Thereby, it is suppressed that the signal component of a smear signal is removed excessively like the past. The correction signal input to the subtraction unit 12 is close to a true smear signal. As a result, the smear component is preferably removed from the image signal output from the subtracting unit 12. On the other hand, when the average smear signal is lower than the threshold value Ref1, the LP signal is used as the correction signal. The LP signal is a signal from which the noise component of the average smear signal has been removed. Therefore, the smear component is preferably removed from the image signal output from the subtracting unit 12. By reconstructing the image based on the image signal from which the smear component has been removed using the LP signal or the NLP signal in this way, a high-quality image can be acquired.

  Note that the NLP signal is used when the level of the smear signal is high, and the quality of the image has deteriorated in the first place. Therefore, even if the high-frequency component (frequency component equal to or higher than the predetermined frequency) of the average smear signal used as the correction signal is not removed, the influence on the image quality does not matter.

[Second Embodiment]
Next, a smear correction unit 10B according to the second embodiment will be described with reference to FIGS.

  In the first embodiment, it is determined whether the level of the average smear signal is higher or lower than the predetermined threshold value Ref1, and either the LP signal or the NLP signal is used as a correction signal based on the determination result. In this embodiment, it is determined whether the absolute value of the difference value of the average smear signal output from the smear signal processing unit 13 is higher or lower than the threshold value Ref2, and based on this determination result, either the LP signal or the NLP signal Is used as a correction signal.

  Unlike the smear correction unit 10A according to the first embodiment, the smear correction unit 10B includes a determination unit 21 instead of the configuration of the determination unit 18.

  As illustrated in FIG. 6, the determination unit 21 includes a first storage unit 22 (FF (Flip-Flop) unit 22), a second storage unit 23 (FF (Flip-Flop) unit 23), a difference calculation unit 24, and a comparison. Part 25. A clock signal is supplied from the timing control unit 20 to the CLK terminals of the FF unit 22 and the FF unit 23.

  The input terminal of the FF unit 22 is connected to the smear signal processing unit 13 via the path P3. The output terminal of the FF unit 22 is connected to the input terminal A of the difference calculation unit 24 and is connected to the input terminal of the FF unit 23. The input terminal of the FF unit 23 is connected to the output terminal of the FF unit 22. Further, the output terminal of the FF unit 23 is connected to the input terminal B of the difference calculation unit 24. The input terminal A of the difference calculation unit 24 is connected to the output terminal of the FF unit 22. The input terminal B of the difference calculation unit 24 is connected to the output terminal of the FF unit 23. The output terminal of the difference calculation unit 24 is connected to the input terminal of the comparison unit 25. An input terminal of the comparison unit 25 is connected to an output terminal of the difference calculation unit 24. The threshold value Ref2 (second threshold value) is input to the other input terminal of the comparison unit 25.

  The FF unit 22 stores the average smear signal output from the smear signal processing unit 13. The FF unit 23 stores the average smear signal (previous average smear signal) stored in the FF unit 22 before the average smear signal (current average smear signal) currently stored in the FF unit 22. The difference calculation unit 24 calculates the difference between the current average smear signal input to the input terminal A and the previous average smear signal input to the input terminal B. Then, the absolute value of the obtained difference value is output to the comparison unit 25. The comparison unit 25 outputs a high-level control signal CS2 when the level of the output signal of the difference calculation unit 24 is higher than the threshold value Ref2. When the level of the output signal from the difference calculation unit 24 is lower than the threshold value Ref2, a low-level control signal CS2 is output. The selection unit 19 outputs the NLP signal as a correction signal based on the high level control signal CS2. The selection unit 19 outputs the LP signal as a correction signal based on the low-level control signal CS2.

  In this embodiment, when the absolute value of the difference value between the current average smear signal and the previous smear signal is higher than the threshold value Ref2, the NLP signal is used as the correction signal. Thereby, it is suppressed that the signal component of a smear signal is removed excessively like the past. The correction signal input to the subtraction unit 12 is close to a true smear signal. As a result, the smear component is preferably removed from the image signal output from the subtracting unit 12. On the other hand, when the absolute value of the difference value is lower than the threshold value Ref2, the LP signal is used as the correction signal. The LP signal is a signal from which the noise component of the average smear signal has been removed. Therefore, the smear component is preferably removed from the image signal output from the subtracting unit 12.

  With reference to FIG. 7, the contribution of the present embodiment to the prior art will be described. As shown in FIG. 7, the horizontal distribution of the true smear signal is indicated by a broken line. The horizontal distribution of the correction signal output from the correction signal generator 16 is indicated by a solid line. Here, in Range3, Range4, and Range5, the correction signal input to the subtraction unit 12 is an NLP signal. In other areas, the correction signal input to the subtraction unit 12 is an LP signal. As indicated by the arrows in FIG. 4, the correction signal input to the subtraction unit 12 is faithful to the true smear signal as compared with the conventional case. In other words, since the average smear signal (NLP signal) from which the high-frequency component is not removed is used as the correction signal at the portion where the smear signal level changes sharply, the signal component of the smear signal is excessively removed by the low-pass filter. There is no. Thus, a signal that has been selectively subjected to a low-pass filter is used (an LP signal that has undergone a low-pass filter is used as a correction signal when desired, and an NLP signal that is not subjected to a low-pass filter is used as a correction signal when not desired) Thus, it is possible to effectively and effectively remove the smear component of the image signal.

  Here, the operation of the smear correction unit 10B will be supplementarily described with reference to the timing chart of FIG.

  Unlike the first embodiment, in the present embodiment, the absolute value of the above difference value is higher than the threshold value Ref2 in the vertical transfer lines VL2 and VL8.

  Therefore, the subtracting unit 12 uses the average smear signal (NLP signal) of the smear signal output from the vertical transfer lines VL2 and 8 as a correction signal as it is, and the image read from each of the vertical transfer lines VL2 and VL8. Remove the smear component of the signal.

  Conversely, in the vertical transfer lines VL1, 3, 4, 5, 6, 7, 9, 10, 11, 12, the absolute value of the above difference value is lower than the threshold value Ref2. Therefore, the subtracting unit 12 filters the signal (LP) obtained by filtering the high-frequency component of the average smear signal of the smear signal read from the vertical transfer lines VL1, 3, 4, 5, 6, 7, 9, 10, 11, 12. Signal) is used as a correction signal, and the smear component of the image signal read from each of the vertical transfer lines VL1, 3, 4, 5, 6, 7, 9, 10, 11, 12 is removed.

  In this embodiment, when the absolute value of the difference value between the current average smear signal and the previous smear signal is higher than the threshold value Ref2, the NLP signal is used as the correction signal. Thereby, it is suppressed that the signal component of a smear signal is removed excessively like the past. The correction signal input to the subtraction unit 12 is close to a true smear signal. As a result, the smear component is preferably removed from the image signal output from the subtracting unit 12. On the other hand, when the absolute value of the difference value is lower than the threshold value Ref2, the LP signal is used as the correction signal. The LP signal is a signal from which the noise component of the average smear signal has been removed. Therefore, the smear component is preferably removed from the image signal output from the subtracting unit 12. Then, by reconstructing the image based on the image signal from which the smear component has been removed using the LP signal or the NLP signal as described above, a high-quality image can be acquired.

[Third Embodiment]
Next, a smear correction unit 10C according to the third embodiment will be described with reference to FIGS.

  In the second embodiment, it is determined whether the absolute value of the difference value of the average smear signal output from the smear signal processing unit 13 is higher or lower than the threshold value Ref2, and based on this determination result, the LP signal or NLP Any of the signals was used as a correction signal. In the present embodiment, the levels of the NLP signal and the LP signal are adjusted according to the level of the difference value of the average smear signal output from the smear signal processing unit 13, and the NLP signal and the LP signal whose levels are adjusted are mixed. The mixed signal is used as a correction signal.

  Unlike the smear correction unit 10B according to the second embodiment, the smear correction unit 10C includes a ratio setting unit 26 instead of the determination unit 21, and includes an addition unit (calculation unit) 30 instead of the selection unit 19. . The smear correction unit 10C further includes a first digital amplifier 28 (DAMP 28) and a second digital amplifier 29 (DAMP 29).

  As illustrated in FIG. 9, the ratio setting unit 26 includes an FF unit 22, an FF unit 23, and a ratio calculation unit 27. As in the second embodiment, an appropriate clock signal is given from the timing control unit 20 to the CLK terminals of the FF unit 22 and the FF unit 23.

  The input terminal of the FF unit 22 is connected to the smear signal processing unit 13 via the path P3. The output terminal of the FF unit 22 is connected to the input terminal A of the ratio calculation unit 27 and is connected to the input terminal of the FF unit 23. The input terminal of the FF unit 23 is connected to the output terminal of the FF unit 22. Further, the output terminal of the FF unit 23 is connected to the input terminal B of the ratio calculation unit 27. The input terminal A of the ratio calculation unit 27 is connected to the output terminal of the FF unit 22, and the input terminal B is connected to the output terminal of the FF unit 23. The output terminal of the ratio calculation unit 27 is connected to the ratio adjustment terminal of the DAMP 28. Further, it is connected to the ratio adjusting terminal of DAMP29. An input terminal of the DAMP 28 is connected to the smear signal processing unit 13, and an output terminal thereof is connected to the input terminal C of the adding unit 30. The input terminal of the DAMP 29 is connected to the output terminal of the low pass filter unit 17. The output terminal of the DAMP 29 is connected to the input terminal D of the adder 30.

  Similar to the second embodiment, the FF unit 22 stores the average smear signal (current smear signal) output from the smear signal processing unit 13. Further, the FF unit 23 stores the average smear signal (previous average smear signal) stored in the FF unit 22 before the average smear signal stored in the FF unit 22 at the present time.

  The ratio calculator 27 subtracts the previous average smear signal input to the input terminal B from the current average smear signal input to the input terminal A. Then, the ratio α (%) is set based on the obtained difference value. Then, the ratio α is communicated to each of DAMP 28 and DAMP 29.

  The DAMP 28 adjusts the level of the NLP signal based on the ratio α. The DAMP 29 adjusts the level of the LP signal based on the ratio α. The output of DAMP 28 and the output of DAMP 29 are added by the adder 30. The added signal is output from the adder 30 as a correction signal.

  Specifically, the DAMP 28 outputs the level value of the NLP signal × α / 100 based on the ratio α input from the ratio calculator 27. On the other hand, the DAMP 29 outputs the LP signal level value × (100−α) / 100 based on the ratio α input from the ratio calculator 27. The adder 30 adds the input from the DAMP 28 and the input from the DAMP 29. Then, the addition unit 30 outputs the addition signal = [level value of NLP signal × α / 100] + [level value of LP signal × (100−α) / 100] as a correction signal.

  As described above, the ratio calculation unit 27 sets the value of the ratio α based on the difference value of the average smear signal. As the ratio α increases, the ratio of the LP signal in the correction signal decreases. Thereby, it is suppressed that the signal component of a smear signal is removed excessively like the past. When the ratio α decreases, the ratio of the NLP signal in the correction signal decreases. Thereby, the noise component in the average smear signal can be sufficiently removed.

  Here, the operation of the smear correction unit 10C will be supplementarily described with reference to the timing chart of FIG.

  As is apparent from FIG. 10, in this embodiment, the difference value obtained by subtracting the average smear signal of the smear signal output from the vertical transfer line VL2 from the average smear signal of the smear signal output from the vertical transfer line VL3. Is +10. The difference value obtained by subtracting the average smear signal of the smear signal output from the vertical transfer line VL3 from the average smear signal of the smear signal output from the vertical transfer line VL4 is +10. The difference value obtained by subtracting the average smear signal of the smear signal output from the vertical transfer line VL4 from the average smear signal of the smear signal output from the vertical transfer line VL5 is −10. The difference value obtained by subtracting the average smear signal of the smear signal output from the vertical transfer line VL5 from the average smear signal of the smear signal output from the vertical transfer line VL6 is −10. The difference value obtained by subtracting the average smear signal of the smear signal output from the vertical transfer line VL9 and the average smear signal of the smear signal output from the vertical transfer line VL8 is +10. The difference value obtained by subtracting the average smear signal of the smear signal output from the vertical transfer line VL9 from the average smear signal of the smear signal output from the vertical transfer line VL10 is zero. The difference value obtained by subtracting the average smear signal of the smear signal output from the vertical transfer line VL11 and the average smear signal of the smear signal output from the vertical transfer line VL10 is −10.

  The period from time t3 to t4 will be described.

  At the time of reading image signals from the vertical transfer lines VL1 and VL2, the ratio α set to DAMP28 and DAMP29 is zero. Therefore, DAMP 28 outputs 0% of the input NLP signal. The DAMP 29 outputs 100% of the input LP signal. The adder 30 adds the 0% NLP signal and the 100% LP signal, and outputs the LP signal 100% as a correction signal. Then, the subtraction unit 12 removes smear components of the read image signal.

  When the image signal is read from the vertical transfer line VL3, the ratio α set to DAMP28 and DAMP29 is 10. Therefore, DAMP 28 outputs 10% of the input NLP signal. The DAMP 29 outputs 90% of the input LP signal. The adder 30 adds the 10% NLP signal and the 90% LP signal, and outputs a mixed signal of the NLP signal 10% + LP signal 90% as a correction signal. Then, the subtraction unit 12 removes smear components of the read image signal.

  When the image signal is read from the vertical transfer line VL4, the ratio α set to DAMP28 and DAMP29 is 20. Therefore, DAMP 28 outputs 20% of the input NLP signal. The DAMP 29 outputs 80% of the input LP signal. The adder 30 adds the 20% NLP signal and the 80% LP signal, and outputs a mixed signal of the NLP signal 20% + LP signal 80% as a correction signal. Then, the subtraction unit 12 removes smear components of the read image signal.

  When the image signal is read from the vertical transfer line VL5, the ratio α set to DAMP28 and DAMP29 is 10. This case is the same as the case of the vertical transfer line VL3 described above. When the image signal is read from the vertical transfer line VL6, the ratio α set to DAMP28 and DAMP29 is 10. This case is the same as the case of the vertical transfer line VL3 described above. At the time of reading image signals from the vertical transfer lines VL7 and VL8, the ratio α set to DAMP28 and DAMP29 is zero. This case is the same as the case of the above-described vertical transfer lines VL1 and VL2. When the image signal is read from the vertical transfer lines VL9 and VL10, the ratio α set to DAMP28 and DAMP29 is 10. This case is the same as the case of the vertical transfer line VL3 described above. At the time of reading image signals from the vertical transfer lines VL11 and VL12, the ratio α set to DAMP28 and DAMP29 is zero. This case is similar to the case of the vertical transfer lines VL1 and VL2 described above.

  In the present embodiment, the NLP signal and the LP signal are mixed based on the difference value between the current average smear signal and the previous smear signal, and this mixed signal is used as a correction signal. More specifically, the ratio calculation unit 27 sets the value of the ratio α based on the difference value of the average smear signal. When the ratio α increases, the ratio of the NLP signal in the correction signal increases. Further, when the ratio α increases, the ratio of the LP signal in the correction signal decreases. Thereby, it is suppressed that the signal component of a smear signal is removed excessively like the past. Conversely, when the ratio α decreases, the ratio of the NLP signal in the correction signal decreases. When the ratio α decreases, the ratio of the LP signal in the correction signal increases. Thereby, the noise component in an average smear signal can also be removed effectively. Then, by removing the smear component from the image signal using the mixed signal in which the NLP signal and the LP signal are mixed, the smear component of the image signal can be suitably removed.

[Fourth Embodiment]
Next, a smear correction unit 10D according to the fourth embodiment will be described with reference to FIGS.

  In the first embodiment, it is determined whether the level of the average smear signal is higher or lower than the predetermined threshold value Ref1, and either the LP signal or the NLP signal is used as a correction signal based on the determination result. In the present embodiment, the level of the average smear signal is determined using two different threshold values Ref3 (third threshold value) and Ref4 (fourth threshold value). Then, based on the determination result, any one of the LP signal, the NLP signal, the LP signal, and the hybrid signal of the NLP signal is used as a correction signal. Note that Ref4 has a higher level than Ref3.

  Unlike the smear correction unit 10A according to the first embodiment, the smear correction unit 10D includes a determination unit 40 instead of the determination unit 21, and includes a calculation unit 44 instead of the selection unit 19.

  As illustrated in FIG. 11, the determination unit 40 includes a comparison unit 41, a comparison unit 42, and a control signal generation unit 43. The input terminal of the comparison unit 41 is connected to the output terminal of the smear signal processing unit 13. The threshold value Ref3 is input to the other input terminal of the comparison unit 41. The input terminal of the comparison unit 42 is connected to the output terminal of the smear signal processing unit 13. The threshold value Ref4 is input to the other input terminal of the comparison unit 42. The output terminal of the comparison unit 41 is connected to the input terminal A of the control signal generation unit 43. The output terminal of the comparison unit 42 is connected to the input terminal B of the control signal generation unit 43. An output terminal of the control signal generation unit 43 is connected to a control terminal of the calculation unit 44.

  The comparison unit 41 outputs the high-level signal 1 when the input average smear signal is at a level higher than the threshold value Ref3. When the input average smear signal is at a level lower than the threshold value Ref3, a low level signal 0 is output. The comparison unit 42 outputs a high-level signal 1 when the input average smear signal is at a level higher than the threshold value Ref4. When the input average smear signal is at a level lower than the threshold value Ref4, a low level signal 0 is output.

  The control signal generator 43 outputs the control signal CS3 based on the outputs from the comparator 41 and the comparator 42. If the input is 00, a low level signal is output. If the input is 01, a middle level signal is output. If the input is 11, a high level signal is output.

The computing unit 44 selects a signal to be output as a correction signal based on the signal level of the control signal CS3. When the control signal CS3 is at a low level, the calculation unit 44 outputs an LP signal as a correction signal. When the control signal CS3 is at the middle level, the calculation unit 44 outputs a mixed signal of the NLP signal and the LP signal as a correction signal. When the control signal CS3 is at a high level, the calculation unit 44 outputs an NLP signal as a correction signal. That is, the control signal generation unit 43 selectively outputs a correction signal according to the signal level of the control signal CS3.

  By using the NLP signal as the correction signal, it is possible to prevent the signal component of the smear signal from being excessively removed as in the related art. Further, by using the LP signal as the correction signal, the noise component in the average smear signal can be effectively removed. In particular, this embodiment is a case where the average smear signal is at a level near one threshold value Ref1 (see the first embodiment) by using a mixed signal of the NLP signal and the LP signal as the correction signal. However, a hybrid signal of the LP signal and the NLP signal that is not deviated from the level of the true smear signal and from which noise components are appropriately removed can be used as the correction signal. Therefore, it is possible to accurately remove the smear component of the image signal.

  Here, the operation of the smear correction unit 10D will be supplementarily described with reference to the timing chart of FIG.

  In the present embodiment, the levels of the smear signal from the vertical transfer lines VL1 to VL3, the smear signal from the vertical transfer line VL7, and the smear signal from the vertical transfer lines VL9 to VL12 are lower than the threshold Ref3. The level of the smear signal from the vertical transfer lines VL4 to VL6 is higher than the threshold value Ref4. The level of the smear signal from the vertical transfer line VL8 is between the threshold value Ref3 and the threshold value Ref4.

  The period from time t3 to t4 will be described.

  When the image signal is read from the vertical transfer lines VL1 to VL3, the control signal CS3 is at a low level. The computing unit 44 outputs an LP signal as a correction signal. Then, the subtraction unit 12 removes the smear component of the image signal using the correction signal.

  At the time of reading the image signals from the vertical transfer lines VL4 to VL6, the control signal CS3 is high bell. The computing unit 44 outputs an NLP signal as a correction signal. Then, the subtraction unit 12 removes the smear component of the image signal using the correction signal.

  When the image signal is read from the vertical transfer line VL7, the control signal CS3 is at the middle level. The calculation unit 44 outputs a mixed signal (for example, LP signal × 50% + NLP signal × 50%) of the LP signal and the NLP signal as the correction signal. Then, the subtraction unit 12 removes the smear component of the image signal using the correction signal.

  When the image signal is read from the vertical transfer lines VL9 to VL12, the control signal CS3 is at a low level. The operation is the same as in the case of the above-described vertical transfer lines VL1 to VL3.

  By using the NLP signal as the correction signal, it is possible to suppress the signal component of the smear signal from being excessively removed as in the related art. Moreover, the noise component in the average smear signal can be effectively removed by using the LP signal as the correction signal. In the present embodiment, by using a mixed signal of the NLP signal and the LP signal as the correction signal, even if the average smear signal is at a level near the threshold Ref1 (see the first embodiment). A hybrid signal of the LP signal and the NLP signal that does not deviate from the level of the true smear signal and from which noise components are appropriately removed can be used as the correction signal. Therefore, it is possible to accurately remove the smear component of the image signal.

[Fifth Embodiment]
Next, a smear correction unit 10E according to the fifth embodiment will be described with reference to FIG.

  Unlike the smear correction unit 10B according to the second embodiment, the smear correction unit 10E includes a determination unit 50 instead of the determination unit 21 (having a calculation unit 51 instead of the selection unit 24 and the comparison unit 25), Further, a calculation unit 44 is provided instead of the selection unit 19.

  Similar to the smear correction unit 10D according to the fourth embodiment, the smear correction unit 10E uses two different threshold values Ref3 (third threshold value) and Ref4 (fourth threshold value). However, instead of determining the level of the average smear signal, the absolute value of the difference value described later is determined. Then, based on the determination result, any one of the LP signal, the NLP signal, the LP signal, and the hybrid signal of the NLP signal is used as a correction signal.

  The output terminal of the FF unit 22 is connected to the input terminal A of the calculation unit 51. The output terminal of the FF unit 23 is connected to the input terminal B of the calculation unit 51. The output terminal of the calculation unit 51 is connected to the control terminal of the calculation unit 44.

The FF unit 22 stores the average smear signal output from the smear signal processing unit 13. The FF unit 23 stores the average smear signal (previous average smear signal) stored in the FF unit 22 before the average smear signal (current average smear signal) currently stored in the FF unit 22. The calculating unit 51 calculates the difference between the current average smear signal input to the input terminal A and the previous average smear signal input to the input terminal B. Then, it is determined whether the absolute value of the obtained difference value is lower than the threshold value Ref3, between the threshold value Ref3 and the threshold value Ref4, or higher than the threshold value Ref4. When the absolute value of the difference value is higher than the threshold value Ref4, the calculation unit 51 outputs a high level control signal CS3. When the absolute value of the difference value is between the threshold value Ref3 and the threshold value Ref4, the calculation unit 51 outputs a middle level control signal CS3. When the absolute value of the difference value is lower than the threshold value Ref3, the calculation unit 51 outputs a low level control signal CS3. The computing unit 44 outputs the NLP signal as a correction signal based on the high-level control signal CS3. Based on the middle level control signal CS3, the calculation unit 44 outputs a mixed signal of the LP signal and the NLP signal (for example, a 50% LP signal and a 50% NLP signal) as a correction signal. Calculation unit 44, based on the control signal CS 3 at a low level, and outputs the LP signal as a correction signal.

  By using the NLP signal as the correction signal, it is possible to prevent the signal component of the smear signal from being excessively removed as in the related art. Further, by using the LP signal as the correction signal, the noise component in the average smear signal can be effectively removed. In the present embodiment, by using a mixed signal of the NLP signal and the LP signal as the correction signal as the correction signal, the absolute value of the difference value has a level near the threshold Ref2 (see the second embodiment). Even in such a case, a mixed signal of the LP signal and the NLP signal that does not deviate from the level of the true smear signal and from which noise components are appropriately removed can be used as the correction signal. Therefore, it is possible to accurately remove the smear component of the image signal.

  The technical scope of the present invention is not limited to the embodiment described above. The technical features of the first embodiment, the second embodiment, the third embodiment, the fourth embodiment, and the fifth embodiment may be added together.

  The CCD driving method, pixel arrangement, vertical transfer line arrangement, etc. are arbitrary. The smear correction unit may be configured as hardware or software. When the smear correction unit is configured by hardware and used as a smear correction circuit, the selection unit 11 is a selection circuit, the subtraction unit 12 is a subtraction circuit (arithmetic circuit) 12, and the smear signal processing unit 13 is a smear signal processing circuit. 13, the smear signal calculation unit 14 is a smear signal calculation circuit 14, the smear signal storage unit 15 is a smear signal storage circuit 15, the correction signal generation unit 16 is a correction signal generation circuit 16, and the low pass filter unit 17 is a low pass filter circuit. 17, the determination unit 18 may be the determination circuit 18, the selection unit 19 may be the selection circuit 19, and the timing control unit 20 may be the timing control circuit 20. The smear signal storage circuit 15 may be a so-called line memory.

It is a schematic block diagram of CCD1 of 1st Embodiment. It is a block diagram of the smear correction unit of 1st Embodiment. 5 is an explanatory diagram for explaining a storage operation by a smear signal processing unit 13; FIG. It is explanatory drawing of 1st Embodiment which shows the relationship between a true smear signal and a correction signal. It is a timing chart for demonstrating operation | movement of the smear correction unit of 1st Embodiment. It is a block diagram of the smear correction unit of 2nd Embodiment. It is explanatory drawing of 2nd Embodiment which shows the relationship between a true smear signal and a correction signal. It is a timing chart for demonstrating operation | movement of the smear correction unit of 2nd Embodiment. It is a block diagram of the smear correction unit of 3rd Embodiment. It is a timing chart for demonstrating operation | movement of the smear correction unit of 3rd Embodiment. It is a block diagram of the smear correction unit of 4th Embodiment. It is a timing chart for demonstrating operation | movement of the smear correction unit of 4th Embodiment. It is a block diagram of the smear correction unit of 5th Embodiment. It is a schematic block diagram of the conventional smear correction unit. It is the conventional explanatory drawing which shows the relationship between a true smear signal and a correction signal.

Explanation of symbols

10A Smear correction unit 11 Selection unit 12 Subtraction unit 13 Smear signal processing unit 14 Smear signal operation unit 15 Smear signal storage unit 16 Correction signal generation unit 17 Low-pass filter unit 18 Determination unit 19 Selection unit 20 Timing control unit P1-P3 Path VL1- VL12 Vertical transfer line HL Horizontal transfer line α Ratio

Claims (5)

Acquire the smear signal output from each of the multiple readout lines,
For each of the plurality of read lines, a correction signal is determined based on the smear signal output from the read line and a signal having a frequency component equal to or lower than a predetermined frequency of the smear signal output from the read line,
A smear correction method in a charge transfer type imaging device that removes a smear component of an image signal output from the readout line using the determined correction signal ,
When the absolute value of the difference value of the smear signal output from the adjacent readout line is higher than a second threshold, the smear signal is determined as the correction signal;
When the absolute value of the difference value of the smear signal output from the adjacent readout line is lower than the second threshold, the signal having a frequency component equal to or lower than a predetermined frequency is determined as the correction signal;
A smear correction method of subtracting the determined correction signal from the image signal . For each of the plurality of readout lines,
Storing the smear signal output from the readout line;
Filter a signal having a frequency component equal to or higher than a predetermined frequency from the stored smear signal,
The smear correction method according to claim 1, wherein the correction signal is determined based on the stored smear signal and the signal having a frequency component equal to or lower than a predetermined frequency. An arithmetic unit that removes a smear component of an image signal output from the readout line using a correction signal generated based on a smear signal output from each of a plurality of readout lines included in the charge transfer type imaging device; ,
A selector for selecting the smear signal output from the readout line ;
A correction signal generating unit that generates the correction signal based on the selected smear signal and a signal having a frequency component equal to or lower than a predetermined frequency of the selected smear signal, and outputs the correction signal to the calculation unit;
With
The correction signal generator is
When the absolute value of the difference value of the smear signal output from the adjacent readout line is higher than a second threshold value, the smear signal is output as the correction signal;
When the absolute value of the difference value of the smear signal output from the adjacent readout line is lower than the second threshold, the signal having a frequency component equal to or lower than a predetermined frequency is output as the correction signal.
The computing unit is
A smear correction unit that subtracts the output correction signal from the image signal.


Obtaining a first smear signal output from the first readout line and having a signal level higher than the first threshold ;
A second smear signal output from a second readout line and having a signal level lower than a second threshold value higher than the first threshold value ;
When the level of the first smear signal is higher than the second threshold, the first smear signal is determined as a first correction signal;
When the level of the first smear signal is between the first threshold and the second threshold, the first smear signal and a signal having a frequency component equal to or lower than a predetermined frequency of the first smear signal are mixed. 1 hybrid signal is determined as the first correction signal,
The determined first correction signal is subtracted from the image signal output from said first read line,
When the level of the second smear signal is lower than the first threshold, a signal having a frequency component equal to or lower than a predetermined frequency of the second smear signal is determined as a second correction signal;
When the level of the second smear signal is between the first threshold and the second threshold, the second smear signal and a signal having a frequency component equal to or lower than a predetermined frequency of the second smear signal are mixed. 2 hybrid signals are determined as second correction signals;
A smear correction method in a charge transfer type imaging apparatus, wherein the determined second correction signal is subtracted from an image signal output from the second readout line. The ratio of the signal of a predetermined frequency below the frequency components in said first composite signal is determined based on a difference value between the smear signal that is output from the read line adjacent the first smear signal and the first read line ,
The ratio of the signal of a predetermined frequency below the frequency components in the second mixed signal is determined based on the difference value between the smear signal that is output from the read line adjacent said second smear signal and the second read line The smear correction method according to claim 4 .

Images