JP2005354292A - Imaging apparatus and imaging method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress color rolling (color flicker) caused by a shift between an exposure period and a lighting period of a fluorescent lamp resulting from a period of a commercial AC power supply. <P>SOLUTION: Changing an output timing of e.g. a vertical synchronizing signal (TMC) by a time in the unit of horizontal lines to vary a time length of a frame for every prescribed frame corrects the shift of the exposure period with respect to the period of the commercial AC power supply. In this case, the period of the commercial AC power supply can be made coincident with the exposure period by setting the period to be corrected and the time length to be corrected. Thus, color rolling can be suppressed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an imaging apparatus provided in, for example, a video camera and a method thereof.

  For example, in a video camera, when a light source having a certain light emission cycle such as a fluorescent lamp is photographed or when a subject irradiated with the light source is photographed, a periodic color change may occur in the moving image. know. This is a phenomenon called color rolling (color flicker).

The generation principle of such color rolling will be described with reference to FIG.
In FIG. 8, FIG. 8 (a) shows a commercial AC power supply cycle. Here, a case where the commercial AC power supply cycle is 60 Hz is illustrated.
FIG. 8B shows changes of the R (red), G (green), and B (blue) components included in the light emitted from the fluorescent lamp over time t. When based on the commercial AC power supply cycle shown in FIG. 8A, the light emission cycle of the fluorescent lamp is 120 Hz as shown.
FIG. 8C shows the period of the vertical synchronizing signal. For example, in the case of the imaging operation by the NTSC system, the frequency is 59.94 Hz.

In general, an image pickup apparatus performs exposure on an image pickup device in accordance with a cycle of a vertical synchronization signal to obtain a picked-up image for each frame (for each field in NTSC).
That is, the exposure timing of the imaging apparatus in this case corresponds to the period of the vertical synchronization signal shown in FIG. 8C as shown by exposure times T1, T2, T3, and T4 in the drawing.
In this way, the exposure operation in the imaging apparatus is made in accordance with the cycle of the vertical synchronization signal, so that the exposure timing (59.94 Hz) in this case is the light emission timing (60 Hz) for two fluorescent lamps. On the other hand, it is gradually shifted by “1 / 599.94-1 / 60” sec.

A gradual shift between the exposure timing and the light emission timing of the fluorescent lamp causes a change in the ratio of RGB components of the fluorescent lamp obtained at each exposure time T1 to T4.
For example, in the exposure time T1 corresponding to the vertical synchronization signal at the time point t1 in the figure, it can be seen that the ratio of the R component among the RGB components of the fluorescent lamp is large.
In contrast, as the subsequent exposure time T2 and exposure time T3 are reached, the light emission timing and the exposure timing of the fluorescent lamp gradually shift as shown in the figure, and the ratio of the R component obtained during the exposure time decreases. It will follow. When the exposure time T4 corresponding to the vertical synchronization signal at the time point t4 is reached, it can be seen that a captured image containing a relatively large amount of B component is obtained.
In this way, a periodic color change occurs over time in a captured image captured under a light source that periodically emits light, such as a fluorescent lamp.

By the way, in the above description, the configuration corresponding to the NTSC system is adopted as the imaging apparatus, and the case where the vertical synchronization signal period (that is, the exposure period to the imaging element) is set to 59.94 Hz is exemplified. In some imaging apparatuses that are widely used in mobile phones and the like, a frame rate such as 10 frames / second or 15 frames / second is employed. That is, a frame rate is set such that an exposure period corresponding to the commercial AC power supply period can be obtained.
According to such a frame rate setting, for example, under a fluorescent lamp that is lit at a commercial power cycle of 60 Hz, color rolling cannot theoretically occur.

The following patent documents describe conventional techniques for suppressing color rolling using AWB (auto white balance) control.
Japanese Patent Laid-Open No. 11-205658

However, strictly speaking, even in an imaging apparatus that employs a frame rate corresponding to a commercial power cycle as described above, the frame cycle may slightly shift from the power cycle.
Such a shift occurs due to the relationship between the frequency of the operation clock employed in the imaging apparatus and the values of the horizontal and vertical counters set based on the number of pixels of the imaging device.
For example, in the case where a frame rate of 10 frames / second is adopted as exemplified above, it is assumed that the system clock is 7.2 MHz and the horizontal and vertical counter values are V = 440 and H = 1640. Try it.
First, in the imaging apparatus, the time length for one frame is as follows when the system clock is F, the vertical counter value (number of lines) is V, and the horizontal counter value (clock) is H.
V × H ÷ F
Is required.
In other words, in this case, the frame rate is 10 frames / second,
V × H ÷ F = 0.1 seconds must be satisfied.

However, under the condition that F = 7.2 MHz is set as the frequency of the system clock as described above, the actual time length for one frame is
440 × 1640 ÷ 7200000 = 0.1002222 ...
Therefore, strictly speaking, one frame is not 0.1 seconds. That is, in this case, a shift of about 0.0002 seconds occurs for each frame.

  In this way, even when the frame rate corresponding to the power supply cycle is set, strictly speaking, the frame rate (frame cycle) may be shifted by about a few percent of the comma. That is, also in this case, a deviation occurs between the power supply cycle and the vertical synchronization signal cycle, and accordingly, a deviation occurs between the lighting cycle of the fluorescent lamp and the exposure timing, and the same principle as described above is used. Rolling will occur.

Therefore, in the present invention, in view of the above problems, the imaging apparatus is configured as follows.
In other words, the image pickup means for obtaining a frame image by periodically exposing the image pickup element based on the vertical synchronization signal, and the output timing of the vertical synchronization signal is changed by a time length that does not coincide with the time length of one frame period. And control means for controlling the exposure timing of the image pickup device in the image pickup means.

In the present invention, the imaging method is as follows.
That is, the imaging method of the present invention is an imaging method in an imaging apparatus including an imaging unit that obtains a frame image by performing periodic exposure on an imaging device based on a vertical synchronization signal, The output timing is changed by a time length that does not coincide with the time length of one frame period, and the exposure timing for the image pickup device in the image pickup means is controlled.

According to the above configuration, the vertical synchronizing signal cycle (the exposure cycle for the image sensor) is changed by a time length that does not match the time length of one frame period. That is, the phase of the frame period can be changed from the original phase by making the change amount not equal to the time length of one frame period.
At this time, as described above, the deviation amount between the frame period (vertical synchronization signal period) at the strict frame rate and the actual frame period is set based on the set clock and the number of pixels of the image sensor. It can be calculated in advance based on the values of the horizontal and vertical counters. Therefore, if the combination of the frame interval for changing the output timing of the vertical sync signal and the amount of change is set so as to absorb the deviation required in this way, the vertical sync signal cycle is corrected to a strict cycle. can do. That is, it is possible to suppress color rolling when a frame rate corresponding to the commercial AC power supply period is set.
Alternatively, even when a frame rate in which the vertical synchronization signal cycle does not match the commercial AC power supply cycle is originally set, the deviation is absorbed as a combination of the above-described frame interval cycle for changing the exposure timing and the amount of change. If it is set to be possible, color rolling can be similarly suppressed.

As described above, according to the present invention, it is possible to match the commercial AC power supply cycle (fluorescent lamp lighting cycle) and the exposure cycle, and it is possible to suppress color rolling.
Further, according to the present invention, although the exposure timing is changed, the exposure time can be controlled as usual, and there is no demerit such that the image quality is lowered for suppressing color rolling.
Further, since auto white balance (AWB) control is not used to suppress color rolling, image quality deterioration related to color rolling suppression can also be avoided in this respect.

Hereinafter, the best mode for carrying out the invention (hereinafter referred to as an embodiment) will be described.
FIG. 1 is a block diagram showing an internal configuration example of an imaging apparatus 1 as a first embodiment of the present invention.
As the imaging device 1 shown in this figure, it is assumed that it is mounted as a camera block provided in a mobile phone, for example.
First, the lens 2 shown in the figure performs focusing and image formation on a CCD (Charge Coupled Device) 3.
The CCD 3 converts light obtained by condensing and imaging by the lens 2 into an electric signal. The CCD 3 is configured so that exposure timing and charge accumulation time can be varied as a so-called electronic shutter function. The exposure timing by the CCD 3 is controlled based on an exposure timing control signal TMG from the microcomputer 7 described later.

  An AFE (Analog Front End processor) 4 performs AGC (automatic gain control) on the electrical signal obtained by the CCD 3. Further, noise removal is performed on the electrical signal supplied from the CCD 3 by a correlated double sampling circuit. Then, the electrical signal thus obtained is converted into a digital signal and supplied to the camera signal processing unit 5.

  The camera signal processing unit 5 converts the electrical signal converted into a digital signal by the AFE 4 as described above into a video signal.

The display / communication control unit 6 performs display control on the video signal obtained by the camera signal processing unit 5 and data with a host computer of an electronic device (in this case, a mobile phone) provided with the imaging device 1. Perform communication control.
For example, based on the video signal obtained by the camera signal processing unit 5, display control is performed on a display device such as an LCD (Liquid Crystal Display) provided in the mobile phone.
Also, control for transferring a command from the host computer to the microcomputer 7 is performed.

The microcomputer 7 includes at least a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory), and performs overall control of the imaging apparatus 1. For example, when a command is input from the host computer side via the display / communication control unit 6 described above, each unit is controlled so that an operation based on the command is obtained.
In particular, in the microcomputer 7 in this case, the exposure timing of the CCD 3 is controlled by an exposure timing control signal TMG generated based on a vertical synchronization signal supplied from a TG (Timing Generator) 10 described below. The Note that exposure timing control as an embodiment will be described later.

  The TG 10 generates various synchronization signals. A system clock (not shown) is input to the TG 10. The TG 10 includes a horizontal counter 8 and a vertical counter 9 for generating a horizontal synchronizing signal and a vertical synchronizing signal based on the system clock.

The horizontal counter 8 counts the system clock, outputs a horizontal synchronization signal every time the count value reaches a predetermined count over value, and resets the count value to zero.
The vertical counter 9 counts horizontal synchronization signals. Then, every time the count value reaches a predetermined count over value, a vertical synchronization signal is output, and the count value is reset to zero.
The horizontal synchronization signal and the vertical synchronization signal generated by the TG 10 are supplied to each necessary unit.

Here, in the imaging apparatus 1 of the first embodiment, as the CCD 3, for example, the number of pixels of 1640 pixels in the horizontal direction (effective pixels + OPB (OPtical Black) + dummy) and 440 pixels in the vertical direction (effective pixels + OPB + dummy) is used. It is supposed to have. In this case, the vertical direction is assumed to be the number of pixels thinned out by half.
Accordingly, the horizontal counter 8 in this case is set to a count over value = 1640. In the vertical counter 9, a count over value = 440 is set. That is, the horizontal counter 8 is configured to output a horizontal synchronizing signal every 1640 clocks, and the vertical counter 9 is configured to output a vertical synchronizing signal every time 440 pulses of the horizontal synchronizing signal are output.

  In addition, a frame rate of 10 frames / second is set as the imaging device 1 in this case. As the system clock, 7.2 MHz is set.

Here, as described above, also in the imaging apparatus 1 in this case, the value of the horizontal counter (count over value) = 1640 (clock), the value of the vertical counter (count over value) = 1440 (line), 10 frames / second A system clock = 7.2 MHz is set in correspondence with a frame rate of (10 fps). According to such a setting, a frame rate of about 10 fps is realized as described above, but a strict frame rate value cannot be obtained.
That is, even in this case, the actual time length of one frame period is
440 × 1640 ÷ 7200000 = 0.100222
Therefore, one frame is not exactly 0.1 seconds, and a shift of about 0.0002 seconds occurs every frame period. The fact that the frame rate does not become strictly 10 fps in this way, that is, the vertical synchronizing signal period does not become strictly 10 Hz, and even in this case, a deviation occurs between the power supply period and the vertical synchronizing signal period. Therefore, there is a difference between the lighting cycle of the fluorescent lamp and the exposure timing, and color rolling occurs.

Therefore, in the embodiment, by changing the setting of the count over value of the vertical counter 9, the deviation between the vertical synchronization signal period and the commercial AC power supply period is corrected, thereby suppressing color rolling. That is, the time length of one frame period is variably controlled in units of horizontal line time by changing the count over value of the vertical counter 9 in this way.
For example, when the count over value of the vertical counter is 440 and the count is decreased to 439, the output timing of the vertical synchronization signal can be advanced by one horizontal line time. That is, in this case, the output timing of the exposure timing control signal TMG can also be advanced by one horizontal line time, and thereby the exposure timing can be advanced by one horizontal line time.

At this time, assuming that the horizontal counter value of the CCD 3 is H (clock) and the system clock is F (Hz), the time length that can be adjusted by increasing or decreasing the count over value of the vertical counter 9 as described above is
H / F (seconds)
It becomes. In other words, according to the setting in this case,
1640 ÷ 7200000 = 0.00022 ...
Thus, adjustment of approximately 0.0002 seconds is possible.

  In this case, as described above, since the time length of one exact frame period at 10 fps = 0.1 seconds, the time length of one actual frame period = 0.002 seconds, the actual frame The cycle is delayed by 0.0002 seconds every frame. According to this, if the count over value of the vertical counter 9 is decreased by 1 and the time length of the frame period is advanced by one horizontal line time every frame as described above, the vertical synchronization signal ( The output timing of the exposure timing control signal TMG) can be matched with the commercial AC power supply cycle. That is, this can suppress color rolling.

  Strictly speaking, in the combination of the horizontal and vertical counter values of the CCD 3 exemplified here and the system clock, the shift for each frame and the horizontal line time do not match. The combinations of horizontal / vertical counter values and system clock frequencies given here are merely examples for the sake of convenience of explanation. In the following, the time length between the shift for each frame and the time for one horizontal line is shown below. The explanation will be continued assuming that they match.

FIG. 2 is a graph showing the exposure timing control operation as the first embodiment in which the time length of one frame period is reduced by one horizontal line time for each frame as described above.
In this figure, the horizontal axis indicates the number of frames, and the vertical axis indicates the number of seconds for correction.
First, the black circles in the figure indicate the accumulation error when uncorrected. That is, the deviation between the frame period and the commercial AC power supply period when the time length correction by the exposure timing control is not performed is shown. As described above, in this case, since a shift of 0.0002 seconds occurs every frame period, the accumulated error at the time of uncorrected is 0.0002 seconds per frame as shown in the figure. It will increase gradually.

A correction amount indicated by a white square in the drawing indicates a time length that is changed to one frame period by changing the count over value of the vertical counter 9. In other words, in this case, the count over value of the vertical counter 9 is decreased by 1, and correction is performed by 0.0002 seconds in each frame. Therefore, the correction amount in each frame is 0.0002 seconds as shown in the figure. It becomes constant.
As described above, the correction of 0.0002 seconds is performed in each frame, so that the corrected error indicated by a white triangle in the figure changes to zero. That is, in this case, the exact frame period is matched in each frame, whereby the frame period and the commercial AC power supply period are matched.

FIG. 3 shows a processing operation for realizing the exposure timing control described above. The processing operation shown in this figure is executed by the microcomputer 7 shown in FIG.
First, in step S101, the count over value of the vertical counter 9 is changed by a predetermined value. That is, when the count over value of the vertical counter 9 set in advance according to the number of vertical pixels (effective pixels + OPB + dummy) of the CCD 3 is Cn, a new value is obtained by adding α (integer) to this Cn. A count over value Cn1 is set.

In step S102, it waits for a vertical synchronization signal from TG10. In other words, in this case, the apparatus waits for the vertical synchronization signal output from the vertical counter 9 based on the count over value Cn1 set as described above.
Then, in response to obtaining the vertical synchronization signal from the TG 10, the exposure timing control signal TMG is output to the CCD 3 in step S103.
When the exposure timing control signal TMG is output in step S103, the process returns to step S102 and again waits for the vertical synchronization signal.

  Thus, according to the exposure timing control operation of the first embodiment, the time length of one frame period in each frame is matched with the time length of one frame period at a strict frame rate, so that strict 10 fps. Frame rate can be maintained. As a result, the commercial AC power supply cycle and the frame cycle are matched, and color rolling can be suppressed.

As the color rolling suppression control of such an embodiment, a strict frame period that can be calculated in advance from a combination of the value of the vertical / horizontal counter based on the number of pixels of the CCD 3 provided in the imaging device 1 and the system clock. This can be realized simply by changing the setting of the count over value of the vertical counter 9 in accordance with the amount of deviation (time length) and the time length for one horizontal line for correcting this.
That is, according to such a control method, for example, color rolling can be suppressed without adding a configuration for detecting a deviation between a commercial AC power supply cycle and an actual frame cycle.

In the embodiment, the exposure timing of the CCD 3 is controlled, but the exposure time control can be performed as usual. That is, there is no demerit that the exposure time is changed due to the color rolling suppression control, and the image quality is thereby lowered.
Furthermore, since automatic white balance (AWB) control is not used for suppressing color rolling, image quality degradation due to control for suppressing color rolling can be avoided in this respect as well.

In the description so far, the time length of the deviation generated for each frame is equal to the time length that can be corrected by changing the count over value by 1, and the count over value is changed by 1 in each frame period. Was given as an example. However, the control of the first embodiment includes a time length that can be corrected per frame by changing the count over value of the vertical counter 9 (that is, a time length that is a multiple of the horizontal line time), and for each frame. If the time length of the generated deviation is made equal, the time length of each frame can be similarly corrected to a strict time length to match the strict frame period.
That is, for example, when the time length of the deviation that occurs every frame is similarly 0.0002 seconds, if the time length that can be corrected by changing the count over value by 1 is 0.0001 seconds, The time length relationship is a multiple relationship. In such a case, by changing the count over value by 2 in each frame, the time length of one frame can be corrected by 0.0002 seconds for each frame. As a result, the exact frame period can be matched as in the case described above.
As can be understood from this, the first embodiment can be applied when the time length of the shift generated for each frame is a multiple of the time length of one horizontal line time.

Here, as described above, in the imaging apparatus 1 of the first embodiment, the length of time that can be corrected per frame by changing the count over value of the vertical counter 9 and the deviation that occurs for each frame. Corresponding to the case where the time length is equivalent, the case where the same amount of correction is performed every frame to suppress color rolling is taken as an example.
However, as the imaging device 1, depending on the combination of the number of horizontal and vertical pixels of the CCD 3 and the system clock, the time length that can be corrected per frame by changing the count over value and the time length of the deviation that occurs for each frame May not be equivalent.
In such a case, if the same amount of correction is performed for each frame as in the first embodiment, there is a possibility that color rolling cannot be effectively suppressed.

  Therefore, as an embodiment, even when the time length that can be corrected per frame by changing the count over value is not equal to the time length of the deviation that occurs for each frame, more effective color rolling As the exposure timing control for suppressing the above, a control operation as shown in FIG. 4 is also possible.

FIG. 4 is a graph showing the exposure timing control operation in the imaging apparatus 1 as the second embodiment, as in the case of FIG.
In FIG. 4, as the exposure timing control operation as the second embodiment, as shown as a correction amount by a white square in the drawing, a predetermined amount is set for every predetermined multiple frames (multiple frames of m). Correction is performed.
That is, in this case, the frame time is not corrected without changing the count over value of the vertical counter 9 from the multiple of m + 1 frame to the next multiple of m-1 frame. Therefore, the error after correction in the figure increases up to the multiple of m minus the first frame in the same manner as the accumulation error when not corrected in the figure. Then, the accumulated error is corrected at once in the multiple frame of m.

For example, as an example in which the time length that can be corrected per frame by changing the count over value is not equal to the time length of the deviation that occurs for each frame, the deviation that occurs per frame is 0.0005 seconds. Assuming a case where one horizontal line time that can be corrected by changing the count over value is 0.0006 seconds, in this case, for example, by changing the count over value by 5 every 6 frames, .0005 × 6 = 0.006 × 5 = 0.003 seconds, so that every 6 frames can be corrected to coincide with a strict frame period.
In other words, the correction is performed so that it matches the exact frame period for each predetermined frame in this way, and in this case as well, accumulation of the deviation between the commercial AC power supply period and the frame period is suppressed, so It is possible to suppress rolling.

By the way, in order to realize such an operation as the second embodiment, means for detecting the multiple frame of m to be corrected is required. For this reason, as the imaging apparatus 1 of the second embodiment, a frame counter 11 is provided in the microcomputer 7 as indicated by the wavy line in FIG.
The frame counter 11 is configured to count the number of pulses of the vertical synchronization signal. Thereby, the number of frames can be counted.

In addition, in the second embodiment, in order to realize the above-described exposure timing control operation, the processing operation as shown in FIG. 5 is executed.
In FIG. 5, the microcomputer 7 in this case is configured to execute a determination process as to whether or not the count value of the frame counter 11 is a multiple of m in step S201 shown in the figure.
If the count value of the frame counter 11 is not a multiple of m and a negative result is obtained, the process proceeds to step S202 to wait for the vertical synchronization signal. That is, in this case, a vertical synchronization signal output based on the count over value Cn set in advance according to the number of pixels of the CCD 3 is waited.
Then, in response to obtaining the vertical synchronization signal, the exposure timing control signal TMG is output in step S203, and the discrimination process in step S201 is executed again.

If a positive result is obtained in step S201 that the count value of the frame counter 11 is a multiple of m, a process of changing the count over value of the vertical counter 9 by a predetermined value is executed in step S204. .
That is, the count over value Cn1, which is a value obtained by adding the predetermined value α (in this case, an integer) to the count over value Cn, is set.

  In the subsequent step S205, a vertical synchronizing signal output based on the count over value Cn1 as described above is waited. If a vertical synchronization signal is obtained, the process proceeds to step S206 to output an exposure timing control signal TMG.

In the subsequent step S207, processing for returning the count over value of the vertical counter 9 is executed.
That is, as the count over value of the vertical counter 9, as shown in the figure, the count over value Cn1—the count over value Cn that becomes the predetermined value α is set. When the count over value is returned to the original value Cn in this way, the determination process in step S201 is executed again.

Here, in the imaging apparatus 1 according to the second embodiment, the value of m indicating the frame interval to be corrected and the predetermined value α may be set based on the following idea, for example.
First, as described above, when the horizontal counter value set in advance based on the number of pixels of the CCD 3 is H and the system clock is F, the length of time that can be corrected by changing the count over value of the vertical counter 9 by one. Is
H ÷ F = H / F
It becomes. That is, the time length that can be corrected by adding the predetermined value α to the count over value Cn of the vertical counter 9 is:
H / F × α = αH / F
It is represented by
On the other hand, if the period shift for each frame that occurs between the exact frame rate set in the imaging apparatus 1 and the frame rate actually obtained is A, correction is performed at multiple frame intervals of m as described above. As the amount of deviation accumulated when
A × m = Am
Can be represented by
From these things, in order to correct | amend so that it may correspond with a strict frame period for every m frame,
αH / F = Am
The value of m and the value of α may be set so that the following relationship holds.

Further, in the embodiment, in addition to the exposure timing control operation of the second embodiment, an operation as the third embodiment as shown in FIG. 6 is possible.
FIG. 6 also shows the exposure timing control operation as the third embodiment in the form of a graph in the same manner as in FIGS.
As the exposure timing control pattern of the third embodiment, as shown as a correction amount in the figure, first, correction is performed with a fixed amount, and then the remaining error is corrected every predetermined frame. It is a thing.

In FIG. 6, in this case, in a frame other than a multiple frame of m (> 2), the count over value of the vertical counter 9 is changed by the first predetermined value α1 to correct the time length of each frame. In this case, the correction amount (time length) based on the first predetermined value α1 is set to be smaller than the time length of the deviation that occurs for each frame. Accordingly, the error after correction in the figure in this case gradually increases with a slope smaller than the uncorrected accumulation error from the multiple of m + 1 frame to the next multiple of m-1 frame. To be increased.
Then, for every multiple frame of m, the count over value is changed by the second predetermined value α2 instead of the first predetermined value α1 for the accumulated error, and this is corrected at once. To do.
According to the control pattern of the third embodiment, color rolling can be suppressed more effectively than the pattern of the second embodiment because the accumulation of shifts for each frame is suppressed. Conceivable.

  Even in this case, α1 and α2 are integers. Also in this case, the frame counter 11 is provided in order to change the count over value every multiple frames of m.

FIG. 7 shows a processing operation for realizing the exposure timing control operation as the third embodiment.
In FIG. 7, as a processing operation in this case, in addition to the processing operation in the second embodiment, the processing in step S <b> 301 shown in the figure is added. That is, the microcomputer 7 in this case first executes a process of changing the count over value of the vertical counter 9 by the first predetermined value α1. That is, the count over value Cn1 is set by adding the first predetermined value α1 to the preset count over value Cn of the vertical counter 9.

  Thereafter, as in the case of the second embodiment, it is determined whether or not the count value of the frame counter 11 is a multiple of m (S302). Then, it waits for a vertical synchronization signal output based on the count over value Cn1 (S303). When the vertical synchronization signal is obtained, the exposure timing control signal TMG is also output in this case (S304).

  When the value of the frame counter 11 is a multiple of m, in this case, the count over value of the vertical counter 9 is set to the count over value Cn2 based on the second predetermined value α2 (S305). That is, the count over value Cn2 that is a value obtained by adding the second predetermined value α2 to the count over value Cn before setting the count over value Cn1 is set.

When the count over value Cn2 is set in this way, a vertical synchronization signal based on the count over value Cn2 is waited (S306), and when the vertical synchronization signal is obtained, TMG is output (S307).
When the exposure timing control signal TMG is output in this way, processing for returning the count over value Cn2 of the vertical counter 9 to the count over value Cn1 is executed (S308), and the discrimination processing in the previous step S302 is executed again. To be done.

Here, in each of the embodiments described so far, the case where the frame rate and the commercial AC power supply cycle are in a correspondence relationship is taken as an example. Correspondingly, by correcting the frame time length so as to coincide with the frame period based on the strict frame rate, the commercial AC power supply period and the frame period (exposure period) are made to coincide with each other, thereby suppressing color rolling. The operation is illustrated.
However, even if the frame rate does not correspond to the commercial AC power cycle, the commercial AC power cycle can be corrected by changing the count over value of the vertical counter 9 and correcting the frame cycle as in the previous embodiments. The color rolling can be suppressed by correcting the deviation between the exposure period and the exposure period.

In order to suppress color rolling, there are two types of commercial AC power supply cycles, 60 Hz and 50 Hz. At this time, for example, if the frame rate is 10 fps, the frame period 10 Hz, 60 Hz, and 50 Hz both correspond to each other. Therefore, color rolling is performed by performing common control to make the frame period coincide with a strict period. Can be suppressed.
However, for example, if 15 fps is set, a correspondence is obtained at 60 Hz, but it is not a correspondence for a commercial AC power supply cycle of 50 Hz, and the frame period is corrected to a strict value. In this control, it is impossible to suppress the color rolling in both.
In such a case, if it is intended to suppress color rolling at both 50 Hz and 60 Hz, control by different patterns may be performed so that different control is possible.
That is, for example, parameters corresponding to an exposure timing control pattern corresponding to 60 Hz and an exposure timing control pattern corresponding to 50 Hz (predetermined value α, predetermined values α1, α2, and m value for determining a correction cycle) are prepared. The color rolling may be suppressed at both 60 Hz and 50 Hz by switching the operation based on these two parameters according to the user operation.

  In each embodiment, the count over value of the vertical counter 9 is varied in correcting the frame period. However, the frame period is similarly corrected by varying the count over value of the horizontal counter 8. be able to.

In the embodiment, when correcting the frame period, a correction amount based on a time length exceeding the time length of one frame period may be set.
However, in this case, when the correction amount matches the time length of one frame period (when α = 440 is set in the example of the embodiment), as a result, the phase of the frame period cannot be changed. . In consideration of this, a time length that does not coincide with the time length of one frame period may be set as the correction amount.

  Further, in the embodiment, the case where the imaging device 1 is applied as a camera block of a mobile phone is illustrated, but the application range of the imaging device of the present invention is not limited to this, and is widely applied to electronic devices in general. be able to.

1 is a block diagram illustrating an internal configuration example of an imaging apparatus as an embodiment of the present invention. It is the figure which showed the exposure timing control operation | movement as 1st Embodiment as a graph. It is the flowchart shown about the processing operation for implement | achieving the exposure timing control operation | movement as 1st Embodiment. It is the figure which showed the exposure timing control operation | movement as 2nd Embodiment as a graph. It is the flowchart shown about the processing operation for implement | achieving the exposure timing control operation | movement as 2nd Embodiment. It is the figure which showed the exposure timing control operation | movement as 3rd Embodiment as a graph. It is the flowchart shown about the processing operation for implement | achieving the exposure timing control operation | movement as 3rd Embodiment. It is a figure for demonstrating the color rolling generation | occurrence | production principle.

Explanation of symbols

  1 imaging device, 2 lens, 3 CCD, 4 AFE, 5 camera signal processing unit, 6 display / communication control unit, 7 microcomputer, 8 horizontal counter, 9 vertical counter, 10 TG, 11 frame counter

Claims (6)

Imaging means for obtaining a frame image by performing periodic exposure based on a vertical synchronization signal to the imaging device;
Control means for changing the output timing of the vertical synchronization signal according to a time length that does not coincide with the time length of one frame period, and controlling the exposure timing of the image pickup device in the image pickup means;
An imaging apparatus comprising: The control means includes
Changing the output timing of the vertical synchronization signal by changing the count over value of the counter for generating the vertical synchronization signal;
The imaging apparatus according to claim 1. The control means includes
Changing the output timing of the vertical synchronization signal by changing the count over value of the vertical counter for generating the vertical synchronization signal;
The imaging apparatus according to claim 1. The control means includes
The imaging apparatus according to claim 1, wherein the output timing of the vertical synchronization signal is changed only in frames at predetermined intervals. The control means includes
In the frames at predetermined intervals, the output timing of the vertical synchronization signal is changed by the time length as the first change amount, and in the frames excluding the frames at predetermined intervals, the output timing of the vertical synchronization signal is set to the second timing. Change according to the length of time as the amount of change,
The imaging apparatus according to claim 1. As an imaging method in an imaging apparatus provided with imaging means for obtaining a frame image by performing periodic exposure based on a vertical synchronization signal to an imaging element,
The output timing of the vertical synchronization signal is changed by a time length that does not coincide with the time length of one frame period, and the exposure timing for the image sensor in the imaging means is controlled.
An imaging method characterized by the above.

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