JP2003032556A - Imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging apparatus provided with a CMOS type imaging device that hardly causes a shake in a photographed image and has an excellent processing efficiency in an output signal of the imaging device. SOLUTION: In this imaging apparatus, the timing when a drive signal for instructing erasure of stored electric charges and a drive signal for instructing output of a signal denoting the stored electric charges are given is made variable by each pixel. The photoelectric conversion time of each pixel is decided according to the color characteristics of illumination light or an illuminance distribution on an imaging device depending on the state of an image forming optical system. Further, the drive sequence of pixels is decided separately from the layout sequence, and pixels in a range corresponding to a part illuminated by a flash light or a range corresponding to a major imaging object are driven nearly at the same time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup device provided with an image pickup device for performing photoelectric conversion, and more particularly to an image pickup device provided with an image pickup device for individually erasing and outputting accumulated charges for each pixel.

[0002]

2. Description of the Related Art The spread of digital cameras that convert light into electric signals to generate image data representing an image is remarkable.
An image sensor used in a digital camera has a configuration in which a large number of pixels that perform photoelectric conversion to generate electric charges and accumulate the generated electric charges are two-dimensionally arranged. There are several types of output. One of them is called a CMOS type.

The CMOS type image pickup device is constructed so that each pixel individually outputs signals to the outside, so that an external signal processing circuit for generating image data can sequentially process the output signals of the pixels. , All pixels output signals at different times. Further, each pixel outputs a signal having a magnitude corresponding to the amount of accumulated charge, not the accumulated charge itself, and holds the accumulated charge even after the signal is output. Therefore, the accumulated charges are erased when the photoelectric conversion is newly started. Although the photoelectric conversion is started by erasing the accumulated charges, the accumulated charges are also erased at different times for each pixel in order to make the photoelectric conversion times of all the pixels uniform.

In the CMOS type image pickup device, since the accumulated charges are erased at the start of photoelectric conversion, it is possible to perform constant exposure, and a shutter for regulating the exposure is unnecessary. On the other hand, it is necessary to control the drive of each pixel individually, and a first drive signal that instructs to erase stored charges, that is, start photoelectric conversion, and a second drive signal that instructs to output a signal representing the stored charges. The signal is applied to each pixel individually. The first and second drive signals are sequentially applied to different pixels,
The period from the application of the first drive signal to the application of the second drive signal corresponds to the photoelectric conversion time, that is, the electronic shutter speed, and is set according to the brightness of the subject. On the other hand, the period from the application of the first and second drive signals to one pixel to the application of another pixel is always set to be constant.

FIG. 22 schematically shows an example of the relationship between the pixel position of the CMOS type image pickup device and the photoelectric conversion time. FIG. 22
In the figure, the horizontal axis t represents time, and the vertical axis y represents the y coordinate on the image sensor. Further, the symbol RST indicates that the charge accumulated in the pixel is erased (the signal of the pixel is reset) by the first drive signal, and the symbol OUT indicates that the signal is output from the pixel by the second drive signal. Is shown.
Note that the x, y coordinates on the image sensor are defined with the center O of the image sensor as the origin and the horizontal (horizontal) direction as x and the vertical (vertical) direction as y, as shown in FIG.

In general, the first and second drive signals are sequentially given from the uppermost pixel row to the lowermost pixel row, and therefore, as shown in FIG. 22, the start time and the end time of photoelectric conversion are Different for each pixel column. For this reason, the photoelectric conversions are for capturing the same image, but the timings do not match. FIG. 23 shows the photoelectric conversion timing in the xy coordinate system. Note that, instead of expressing a fine difference in time, in FIG. 23, the time is schematically represented by four shades. On the other hand, the photoelectric conversion time, that is, the length of time for photoelectric conversion is constant for all pixels, as shown by uniform density in FIG.

In each pixel column, the first and second drive signals are sequentially applied from the leftmost pixel to the rightmost pixel. Therefore, the photoelectric conversion time also differs within the pixel column. However, the difference in the photoelectric conversion timing within each pixel column is small.

The difference in the photoelectric conversion timing between the pixel columns does not cause any particular problem when photographing a stationary subject. However, when the object to be photographed moves, the image of the object to be photographed is distorted. For example, when the object to be photographed descends or rises in the vertical direction, it expands or contracts in the vertical direction, and when it moves in the horizontal direction, the positions of the upper part and the lower part are displaced and the distortion occurs. Such image distortion increases as the difference in photoelectric conversion timing increases.

In photographing in a dark environment, flash light is emitted during photoelectric conversion to illuminate the object to be photographed. However, the difference in the photoelectric conversion timing for each pixel row causes a problem even when flash light is emitted. . This is because the flash emission time is extremely short, and if the flash light is not emitted within the photoelectric conversion time of all the pixel columns, an image of the imaging target that is not partially illuminated will be captured.

An example is shown in FIG. In this, the photoelectric conversion timing is set as shown in FIG. 22, and the flash light is emitted immediately before the photoelectric conversion time of the uppermost pixel row ends. The symbol FL indicates flash emission. In this case, the lower pixel row starts photoelectric conversion after the flash emission ends, and the captured image is illuminated by the flash light and the portion B as shown in FIG. There will be a portion D that has not been processed.

For this reason, in the conventional digital camera having the CMOS type image pickup device, as shown in FIG. 27, when the flash light is emitted, the photoelectric conversion time is lengthened so that the pixels at the upper end, the pixel row, and the lower end are pixelated. The photoelectric conversion times of the columns are partially overlapped. As a result, all the pixels can be brought into a state where photoelectric conversion is performed when the flash light emission FL is performed, and as shown in FIG. 28, a portion D which is not illuminated by the flash light from the captured image.
Can be eliminated. However, if the photoelectric conversion time is lengthened, there is a problem in that the quality of the image is deteriorated due to camera shake of the user holding the camera.

[0012]

As described above, the CMO
In a conventional image pickup apparatus including an S-type image pickup element, the order of pixels for performing photoelectric conversion is fixed, and the photoelectric conversion time is also the same for all pixels. Therefore, when the object to be photographed moves or when the object to be photographed is illuminated with flash light, distortion or blurring of the image is caused.

The CMOS type image pickup device is originally capable of individually controlling the driving of pixels. The present invention has been made in view of this point, and an object of the present invention is to provide an efficient imaging apparatus that does not involve the above-mentioned inconvenience and further reduces the processing performed on the output signal of the imaging element.

[0014]

In order to achieve the above object, the present invention provides a two-dimensional array of pixels that generate and store charges by photoelectric conversion and output a signal representing the amount of accumulated charges. While the image sensor is exposed, it has an image sensor that erases accumulated charge and outputs a signal individually for each pixel, and an image forming optical system that forms an image of light from a subject on the image sensor. By supplying the first drive signal for instructing to erase the accumulated charge and the second drive signal for instructing the output of the signal to the pixel of the image sensor, and generating the image data from the signal output from the pixel of the image sensor. In an imaging device that captures an image, the order of pixels that provide the second drive signal is different from the order of the two-dimensional array of pixels. That is, the signal output order is different from the pixel array order.

Specifically, the second driving is performed on a pixel located within a range substantially corresponding to the range of the object to be photographed in which the imaging optical system is in focus, before a pixel located outside the range. Try to give a signal. Normally, the user focuses the taking lens on the main part of the entire subject to be photographed, and in this way, the signal representing the subject to be photographed is preferentially output over the signal representing the background, and the main subject to be photographed. The difference in the timing of photoelectric conversion with respect to the target becomes small. Therefore, even when the main subject is moving, blurring and distortion are unlikely to occur.

Further, when the flash light is emitted between the application of the first drive signal and the application of the second drive signal, the position is within a range substantially corresponding to the range of the object to be photographed illuminated with the flash light. The second drive signal is given to the pixel to be turned on before the pixel located outside the range. In this case, the signal representing the range illuminated by the flash light in the entire subject to be photographed is preferentially output, and the difference in the timing of photoelectric conversion with respect to the range is reduced. Therefore, it becomes possible to shorten the photoelectric conversion time, and it becomes difficult for camera shake to occur.

Further, the second drive signal is applied to the pixel located in the central part of the image pickup device before the pixel located in the peripheral part. In many cases, the user shoots with a composition in which the main object to be photographed is located in the center, and by doing this, even when the main object to be photographed is moving,
It becomes easy to suppress the occurrence of blurring and distortion. Also, when adjusting the focus of the imaging optical system or adjusting the photoelectric conversion time of the pixels of the image sensor based on the captured image, it is possible to quickly obtain the central signal that carries more important information, and adjust Can be done quickly.

In order to achieve the above-mentioned object, the present invention also has a two-dimensionally arranged pixel which generates and accumulates charges by photoelectric conversion and outputs a signal representing the amount of accumulated charges. Equipped with an image sensor that individually erases and outputs signals for each pixel, and an imaging optical system that focuses light from the object to be imaged on the image sensor, and erases accumulated charges while the image sensor is exposed. A first drive signal for instructing the image pickup and a second drive signal for instructing the output of the signal are given to the pixels of the image pickup device, and image data is generated from the signals output from the pixels of the image pickup device In the device, the time from application of the first drive signal to application of the second drive signal is different between pixels. That is, the photoelectric conversion time is not the same for all pixels.

Specifically, the time from the application of the first drive signal to the application of the second drive signal is determined according to the illuminance of each pixel based on the state of the imaging optical system. In general, the intensity of light that has passed through the imaging optical system tends to decrease as it moves away from the optical axis, and if the photoelectric variation time of all pixels is the same, the intensity of the signal output by the pixel is corrected according to the position of the pixel. Need to do. However, this makes it unnecessary to correct the signal strength.

Further, the pixel of the image pickup device is configured to include a plurality of types having different wavelengths of light for photoelectric conversion, and the time from the application of the first drive signal to the application of the second drive signal is , According to the type of each pixel. For example, in order to capture a color image, three types of pixels that selectively photoelectrically convert red light, green light, and blue light are included, and the photoelectric conversion times of these three types of pixels are individually determined. Generally, the sensitivity of a pixel varies depending on the wavelength of light to be photoelectrically converted. Therefore, if the photoelectric conversion time of all pixels is the same, in order to obtain an image with proper white balance, the intensity of the signal output by the pixel Need to be corrected according to the type of pixel. Further, when the signal strength is corrected, some pixels have a relatively narrow dynamic range. But,
By determining the photoelectric conversion time according to the type of pixel, it is possible to obtain an image with an appropriate white balance without correcting the signal intensity, and it is possible to make the dynamic range uniform.

In this case, the time from the application of the first drive signal to the application of the second drive signal may be determined according to the color characteristic of the light illuminating the object to be photographed. By doing so, for example, an image with an appropriate white balance can be obtained regardless of whether the illumination light is natural light or artificial light.

The present invention also has a two-dimensionally arranged pixel that generates and accumulates charges by photoelectric conversion and outputs a signal representing the amount of accumulated charges, and erases accumulated charges and outputs signals. A first drive signal for instructing to erase accumulated charges while exposing the image sensor And a second drive signal for instructing the output of a signal to the pixels of the image sensor to generate an image data from the signals output from the pixels of the image sensor, thereby capturing an image. It is assumed that the timing of applying the pixel and the timing of applying the second drive signal are variable for each pixel. By doing so, it becomes possible to flexibly control the drive of the pixel, and it is possible to adopt an arbitrary drive control. For example, all of the above image pickup devices can be realized by a single image pickup device.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an image pickup apparatus of the present invention will be described below with reference to the drawings. The configuration of the digital camera 1 of the first embodiment is schematically shown in FIG.
The digital camera 1 includes a taking lens 11, an image sensor 12,
Signal processing unit 13, storage unit 14, recording unit 15, drive unit 1
6, lens / aperture drive unit 17, lens information detection unit 18,
The operation unit 19, the control unit 20, and the light source color detection unit 21 are included.

The taking lens 11 forms an image of the light from the subject on the image pickup device 12. The taking lens 11 includes a diaphragm (not shown) with a variable aperture that regulates the diameter of the light beam, and the amount of light received by the image sensor 12 can be adjusted by the aperture diameter of the diaphragm. The image sensor 12 is an area sensor in which a large number of pixels that perform photoelectric conversion are two-dimensionally arranged. The image sensor 12 is a CMOS type, and each pixel is provided with an output path for outputting a signal representing accumulated charges to the outside and an input path for receiving a drive signal.

Each pixel of the image sensor 12 has red (R) light,
A color filter that selectively transmits green (G) light and blue (B) light is provided, and all pixels are classified into three types that photoelectrically convert R light, G light, and B light. ing. The arrangement of these three types of pixels is shown in FIG.

The signal processing unit 13 converts the analog signal output from the pixel of the image pickup device 12 into a digital signal, and also performs various processes such as pixel interpolation and γ correction on the converted digital signal so that the image pickup device 12 is processed. Image data representing the image formed on the. A color image is captured by a series of processes from photoelectric conversion by the image sensor 12 to generation of image data by the signal processing unit 13.

The storage unit 14 temporarily stores the image data generated by the signal processing unit 13. The recording unit 15 includes the storage unit 1.
The image data stored in 4 is compressed and recorded in a removable recording medium such as a memory card. The recording is performed by the control unit 20.
Follow the instructions in.

The drive section 16 gives a drive signal to the image pickup device 12 to control the operation of each pixel. Specifically, a first drive signal S1 instructing to erase the accumulated charge in the pixel and a second drive signal S2 instructing to output a signal from the pixel are provided. First drive signal S1 and second drive signal S2
Are individually given to each pixel of the image sensor 12.

The digital camera 1 does not have a mechanical shutter that regulates the exposure of the image pickup device 12, and the image pickup device 12 is always exposed, but each pixel is photoelectrically converted to generate image data. Is performed from when the first drive signal S1 is given to when the second drive signal S2 is given. The driving unit 16 outputs the first driving signal S1 to each pixel.
The time from the application of the signal to the application of the second drive signal S2 corresponds to the photoelectric conversion time, that is, the shutter speed.
The exposure amount of each pixel during photoelectric conversion is determined by the aperture of the taking lens 11 and the photoelectric conversion time.

The time when the first drive signal S1 and the second drive signal S2 are given to each pixel is variable, and the order of pixels to start photoelectric conversion, the order of pixels to output signals, and the photoelectric conversion time of each pixel. Can be set arbitrarily. These are controlled by the control unit 20.

The lens / diaphragm drive unit 17 is used for the photographing lens 1.
The movable lens group is moved to adjust the focal position and the focal length of No. 1 and the aperture diameter of the diaphragm is adjusted. The lens information detection unit 18 detects the position of the movable lens group of the taking lens 12 and outputs it to the control unit 20.

The operation unit 19 is composed of some operation members operated by the user, and has a button for instructing the start of photographing, a button for instructing to photograph and record an image for recording, and the digital camera 1. A dial etc. for setting the operation mode are included. The light source color detection unit 21 detects color characteristics of illumination light that illuminates an object to be photographed.

The control unit 20 controls the overall operation of the digital camera 1 according to the instruction given by the user via the operation unit 19 and the set operation mode. For example, the first and second drive signals S1 and S2 from the drive unit 16
In addition to setting the output timing of, the lens / aperture drive unit 17 is caused to adjust the focal position and focal length of the taking lens 12 based on the output from the lens information detection unit 18, and the aperture diameter of the aperture is adjusted. From the color characteristics of the illumination light detected by the light source color detection unit 21, conditions for obtaining an image with proper white balance are calculated.

In the digital camera 1, the signals output from the respective pixels directly represent an image with an appropriate white balance, and the signal processing unit 13 does not adjust the signal intensity for white balance adjustment. By not adjusting the signal intensity in the signal processing unit 13, the entire dynamic range of the pixels for each color light is reflected in the image data, and a color image with a fine gradation can be provided.

For this reason, the control unit 20 controls the image pickup device 12
The photoelectric conversion time of each pixel is determined according to the type of pixel and the color characteristic of the illumination light detected by the light source color detection unit 21, and the difference in the transmittance of the color filter and the difference in the photoelectric conversion efficiency of the pixel for each color light are calculated. In addition to the correction, the difference in the color temperature of the illumination light that changes depending on the shooting environment is corrected.

FIG. 3 shows an example of the relationship between the pixel position and the photoelectric conversion time in the digital camera 1. This is when the color temperature of the illumination light is low, that is, when it is appropriate to make the photoelectric conversion time of the B light pixel the longest and the photoelectric conversion time of the R light pixel the shortest. . FIG. 4 shows a flow of control processing for driving a pixel in the example of FIG.

First, the color characteristic of the illumination light is detected (step # 105), and the photoelectric conversion time of the pixel for each color light is determined (# 110). Then, according to the length of the photoelectric conversion time determined in step # 110, application of the first drive signal S1 to the pixels for B light is started (# 115), and after a short waiting time (# 120), for G light. The first drive signal S1 is started to be applied to the pixels of (# 125), and after waiting for a short time (# 125).
130), the application of the first drive signal S1 to the pixels for R light is started (# 135). The first drive signal S1 is
The pixel rows are given in order from the uppermost pixel row to the lowermost pixel row, and in each pixel row from the leftmost pixel to the rightmost pixel.

Next, according to the photoelectric conversion time determined in step # 110, after waiting for a short time (# 140), application of the second drive signal S2 to the R light pixels is started (# 14).
5) After waiting for a short time (# 150), application of the second drive signal S2 to the G light pixels is started (# 15).
5) After waiting for a short time (# 160), application of the second drive signal S2 to the B light pixels is started (# 16).
5). The order of the pixels that give the second drive signal S2 is the same as the order of the pixels that give the first drive signal S1.

In this control, since the G light pixel and the R light pixel also perform photoelectric conversion while the B light pixel that requires the longest time is performing photoelectric conversion, the photoelectric conversion depending on the pixel type is performed. The difference in conversion time is small. Therefore, it is not necessary to adjust the white balance afterwards, and it is possible to suppress the occurrence of color misregistration even when the object to be photographed moves.

Hereinafter, digital cameras of other embodiments will be described, but the same or similar components as those of the digital camera 1 described above will be denoted by the same reference numerals, and redundant description will be omitted.

The configuration of the digital camera 2 of the second embodiment is schematically shown in FIG. The digital camera 2 includes an illuminance distribution storage unit 22 that stores the relationship between the focal position of the taking lens 11, the focal length, the aperture diameter of the diaphragm, and the illuminance distribution on the image sensor 12.

In general, the intensity of light focused by the imaging optical system decreases as the distance from the optical axis increases. Therefore, the image sensor 1
If the photoelectric conversion times of the second pixel are all the same, the output signal of the pixel located in the peripheral portion has a lower intensity than the output signal of the pixel located in the central portion, so that an image with uniform brightness can be obtained. Therefore, it is necessary to correct the intensity of the output signal of the pixel according to the position of the pixel. With the digital camera 2,
By setting the photoelectric conversion time of the image pickup element 12 according to the illuminance distribution on the image pickup element 12, that is, the setting state of the image pickup lens 11, it is not necessary to correct the intensity of the output signal of the pixel.

FIG. 6 shows an example of the relationship between the pixel position and the photoelectric conversion time in the digital camera 2. In this example, the photoelectric conversion time is set longer for a pixel column closer to the upper end or the lower end of the image sensor 12. FIG. 7 shows a flow of control processing for driving a pixel.

First, the exposure condition of the image pickup device 12 is determined based on the image already taken (step # 205), and the aperture of the taking lens 11 is set to an appropriate aperture diameter (# 21).
0). Then, the stored information is read from the illuminance distribution storage unit 22, and based on the focus position and the focal length of the photographing lens 11 and the set aperture diameter of the diaphragm, which are known from the output of the lens information detection unit 18, on the image sensor 12. The illuminance distribution is calculated (# 215). Then, the photoelectric conversion time of each pixel column is set to be substantially inversely proportional to the average illuminance (# 2
20), the application of the first drive signal S1 is started (# 225). The first drive signal S1 is given in order from the pixel having the longest photoelectric conversion time, that is, from the pixel row near the upper end and the lower edge toward the central pixel row.

After waiting for the photoelectric conversion time of the upper and lower pixel rows (# 230), application of the second drive signal S2 is started (# 235). The second drive signal S2 is also given in the same order as the first drive signal S1. At this time, the timing for applying the first drive signal S1 to each pixel column is determined so that the cycle of the second drive signal S2 applied to each pixel column is constant. This is because the processing in the signal processing unit 13 can be performed at a constant cycle.

The photoelectric conversion time of each pixel of the image pickup device 12 under the above control is shown in FIG. 8 in the xy coordinate system. Note that instead of expressing a fine difference in time length, FIG. 8 schematically illustrates the time length in four shades.

Here, the photoelectric conversion time differs in the vertical direction (y-axis direction) of the image pickup device 12, but the first and second drive signals S1 and S2 are transmitted from the pixel columns at the left and right ends to the center. May be given in order toward the pixel rows of, and the photoelectric conversion time may be different in the left-right direction (x-axis direction). In that case, the photoelectric conversion time of each pixel is xy
The coordinate system is schematically shown in FIG.

The photoelectric conversion time may be set for each pixel instead of being set for each pixel column. An example of the relationship between the position of the pixel and the photoelectric conversion time in that case is shown in FIG.
, And the photoelectric conversion time of each pixel is shown in FIG.
Is schematically shown in. In FIG. 10, the vertical axis r indicates the image sensor 1
2 represents the distance (x ² + y ² ) ^1/2 from the center O. Signal output from the pixels is performed in the order of forming concentric circles.

It is also possible to reverse the order of the pixels supplying the second drive signal S2 to the order of the pixels supplying the first drive signal S1. That is, the second drive signal S2 can be applied from the central pixel to the peripheral pixels.
By doing so, the difference in photoelectric conversion timing between pixels is reduced, and the occurrence of blurring can be suppressed.

The structure of the digital camera 3 of the third embodiment is schematically shown in FIG. The digital camera 3 includes a light emitting unit 23 that emits flash light, and emits flash light from the light emitting unit 23 to illuminate an object to be photographed when photographing in a dark environment.

As described above, if all the pixels are photoelectrically converted when the flash light is emitted, the photoelectric conversion time is inevitably lengthened and camera shake is likely to occur. In order to avoid this inconvenience, in the digital camera 3, only the pixels within the range corresponding to the range illuminated by the flash light among the pixels of the image sensor 12 are in the state of performing photoelectric conversion when the flash light is emitted. Since it is sufficient, the pixels within the range are given the second drive signal S2 preferentially,
Reduce the difference in photoelectric conversion timing. Further, shooting with or without flash light emission is performed in advance, and the range illuminated by the flash light is known from the difference in brightness of the images obtained by these shootings.

FIG. 13 shows an example of an image obtained by pre-shooting for knowing the range illuminated by the flash light. FIG.
In (a), an image obtained by shooting without flash emission is shown, and (b) is an image obtained by shooting with flash emission. Obj is the main object to be photographed, and only this is illuminated with flash light. In the example of FIG. 13, a range P in which the second drive signal S2 is preferentially given when the flash light is actually emitted to shoot is shown in FIG. 14, and the first drive signal S1 and the second drive signal S2 are given. The pixel order is shown in FIG. Further, FIG. 16 schematically shows the relationship between the pixel position and the photoelectric conversion time.

FIG. 17 shows the flow of control processing for driving the pixels in the digital camera 3. First, pre-shooting without flash emission and pre-shooting with flash emission are performed (steps # 305, # 310). Next, the range of the image sensor 12 including the range of the photographing target illuminated with the flash light is set (# 315). Further, the photoelectric conversion time is determined based on the image obtained by the shooting without flash emission in step # 305 (# 320), and the shooting lens 11
The diaphragm is set to an appropriate aperture diameter (# 325). The photoelectric conversion time is set so that there is an overlapping period for all the pixels within the range set in step # 315.

After setting the aperture, the application of the first drive signal S1 to the pixels is started (# 330). Then, it stands by for a short time (# 335), and when all the pixels within the range set in step # 315 are in the state of performing photoelectric conversion, flash light is emitted (# 340). After that, if necessary, the device waits for a short time (# 345), and the first drive signal S1
When the photoelectric conversion time of the pixel given first
Providing the second drive signal S2 is started (# 35).
0).

In the digital camera 3, even in the normal photographing in which the flash light is not emitted, the first and second drive signals S are preferentially given to the pixels within the range substantially corresponding to the main subject to be photographed.
1 and S2 are given to reduce the difference in photoelectric conversion time between these pixels and prevent blurring due to movement of the object to be photographed. FIG. 18 shows the flow of the pixel drive control processing in this case.

First, the distance to each part of the object to be photographed and the brightness of each part are measured (steps # 405 and # 410), and the main object to be photographed and the background are discriminated from the measurement result (# 415).
Next, the range of the image sensor 12 including the main object to be photographed is set (# 420), and the application of the first drive signal S1 is started (# 425). The first drive signal S1 is given to the pixels in the order shown in FIG. 15, for example. Then, after the first drive signal S1 is first applied and the photoelectric conversion time elapses (# 430), the application of the second drive signal S2 is started (# 435). The second drive signal S2 is applied to the pixels in the same order as the first drive signal S1.

The digital camera 4 of the fourth embodiment will be described. The digital camera 4 according to the present embodiment has the image sensor 12 of the digital camera 2 according to the second embodiment vertically arranged.
It is equally divided into left and right and divided into four sections, and four sections corresponding to the four sections are provided up to a portion of the signal processing unit 13 that converts the output signal of the pixel into a digital signal. is there. The second drive signal S2 is sequentially given from the pixels near the center of the image sensor 12 to the peripheral pixels.

FIG. 19 shows the order of the pixels which give the second drive signal S2. First, it is applied to the pixel at the center (0,0) of the image pickup device 12, then to the two pixels of (0, ± 1), and further to the two pixels of (± 1,0). After that, 2 pixels of (0, ± 2), 4 pixels of (± 1, ± 1), 2 pixels of (± 2,0), 2 pixels of (0, ± 3), (± 1, ± 2) 4 pixels,
4 pixels of (± 2, ± 1) and 2 pixels of (± 3,0) are given while increasing k along a straight line of y = ± x ± k. At this time, the second drive signal S2 is simultaneously applied to the pixels having the same absolute value of x coordinate and y coordinate. Although signals are simultaneously output from the respective sections, there is no problem because the signal processing unit 13 has a configuration capable of performing parallel processing, and rather, the signal output from the image pickup device 12 can be promptly performed. Further, since the signal output timings of the pixels on the boundary between the adjacent sections match, the image does not become discontinuous.

FIG. 20 shows the relationship between the pixel position and the photoelectric conversion period.
Is schematically shown in. In FIG. 20, (a) is for increasing the photoelectric conversion time, and (b) is for decreasing the photoelectric conversion time. Note that K is the value of k corresponding to the pixels at the four corners of the image sensor 12. The first drive signal S1 is given to all the pixels at the same time when the photoelectric conversion time is lengthened, and is given in the same order as the second drive signal S2 when the photoelectric conversion time is shortened. Further, as described above, in consideration of the illuminance distribution on the image sensor 12, the pixel farther from the center O (larger k) has a longer photoelectric conversion time.

Similarly to the digital camera 2 of the second embodiment, the digital camera 4 does not require correction of the signal intensity in the signal processing unit 13, and therefore, the entire dynamic range of all pixels should be used. Therefore, it is possible to obtain a fine gradation image. Moreover, the time required for signal output from the image sensor 12 is about 1/4, and the difference in photoelectric conversion timing between pixels is reduced, so that the obtained image has a substantially high electronic shutter speed with little distortion or blurring. Will be realized. It is also possible to quickly obtain information for adjusting the focus of the taking lens 11 and adjusting the photoelectric conversion time of the image sensor 12 from the taken image.

In many cases, the user selects a composition in which the main object to be photographed is located near the center of the entire object to be photographed. Therefore, in the digital camera 4 that sequentially outputs signals from the central pixel of the image sensor 12, the difference in photoelectric conversion timing with respect to the main subject to be photographed becomes small, unless the user selects a special composition. Image distortion and blurring can be further suppressed.

It should be noted that, in order to make the features of the present invention easy to understand, the digital cameras of different configurations are used in the above-described embodiments, but the controls of the embodiments can be combined. For example, the control of the first embodiment that determines the photoelectric conversion time according to the color characteristics of the illumination light, and the second determination of the photoelectric conversion time according to the illuminance distribution on the image sensor,
The control of the fourth embodiment may be combined with the first control.
The control of the second embodiment or the control of the second embodiment or both of them may be combined with the control of the third embodiment that preferentially determines a pixel that outputs a signal. The reason why such flexible control is possible is that the timing of applying the first drive signal S1 and the second drive signal S2 to the pixels of the image sensor 12 is variable for each pixel.

[0063]

According to the image pickup device of the present invention, the order of the pixels providing the second drive signal for instructing the signal output is different from the order of the two-dimensional array of the pixels. It is possible to reduce the size, and it becomes easy to align the photographing times of the portions corresponding to those pixels in the entire photographing target.

The second drive signal is applied to the pixels located within the range substantially corresponding to the range of the object to be photographed in which the imaging optical system is in focus, before the pixels located outside the range. Then, even when the main object to be photographed focused by the user is moving, blurring or distortion is unlikely to occur.

When the flash light is emitted between the time when the first drive signal for instructing the erasing of the accumulated charge is given and the time when the second drive signal is given, it corresponds approximately to the range of the photographing target illuminated by the flash light. If the second drive signal is given to the pixels located within the range before the pixels located outside the range, even if the photoelectric conversion time is shortened, the entire target to be photographed is illuminated with the flash light. The area to be illuminated can be illuminated reliably within the photoelectric conversion time. Therefore, camera shake is less likely to occur.

If the second drive signal is given to the pixel located in the central part of the image pickup device before the pixel located in the peripheral part, even when the main subject is moving,
It becomes easy to suppress the occurrence of blurring and distortion. Further, when adjusting the focus of the imaging optical system or the photoelectric conversion time of the pixels of the image sensor based on the captured image, it is possible to quickly obtain the signal of the central portion that carries more important information, The adjustment can be done quickly.

In the image pickup device of the present invention, the time from the application of the first drive signal instructing to erase the accumulated charge to the application of the second drive signal instructing the output of the signal differs between pixels. The time differs depending on the pixel, and this can be reflected in the brightness and color of the image.

When the time from the application of the first drive signal to the application of the second drive signal is determined according to the illuminance of each pixel based on the state of the imaging optical system, it depends on the state of the imaging optical system. It is possible to correct the unevenness of the illuminance, and it becomes unnecessary to correct the intensity of the output signal of the pixel later.

In the configuration in which the pixels of the image pickup device include a plurality of types having different wavelengths of light for photoelectric conversion, the time from the application of the first drive signal to the application of the second drive signal is If determined according to the type of pixel, it is not necessary to adjust the white balance when processing the pixel signal. Further, the dynamic range of all pixels becomes uniform, and a color image with rich gradation can be obtained.

Further, after applying the first drive signal, the second drive signal is applied.
If the time until the drive signal is given is determined according to the color characteristics of the light that illuminates the object to be photographed, an image with an appropriate white balance can be obtained regardless of the color characteristics of the illumination light.

In the image pickup apparatus of the present invention, the time for giving the first drive signal for instructing to erase the accumulated charge and the time for giving the second drive signal for instructing the output of the signal are variable for each pixel. Drive control can be performed flexibly,
The control method of driving the pixel can be arbitrarily set and changed. For example, all the above-described image pickup devices having their respective characteristics can be realized by a single image pickup device.

[Brief description of drawings]

FIG. 1 is a block diagram schematically showing the configuration of a digital camera according to a first embodiment.

FIG. 2 is a diagram showing an arrangement of three types of pixels of an image sensor in the digital camera of the first embodiment.

FIG. 3 is a diagram showing an example of a relationship between a pixel position and a photoelectric conversion time in the digital camera of the first embodiment.

FIG. 4 is a flowchart showing a flow of pixel drive control processing in the digital camera of the first embodiment.

FIG. 5 is a block diagram schematically showing the configuration of a digital camera according to a second embodiment.

FIG. 6 is a diagram showing an example of a relationship between pixel positions and photoelectric conversion timings in the digital camera of the second embodiment.

FIG. 7 is a flowchart showing the flow of a pixel drive control process in the digital camera of the second embodiment.

FIG. 8 is a diagram schematically showing an example of a photoelectric conversion time of each pixel in the digital camera of the second embodiment.

FIG. 9 is a diagram schematically showing another example of the photoelectric conversion time of each pixel in the digital camera of the second embodiment.

FIG. 10 is a diagram showing another example of the relationship between pixel positions and photoelectric conversion timings in the digital camera of the second embodiment.

FIG. 11 is a diagram schematically showing another example of the photoelectric conversion time of each pixel in the digital camera of the second embodiment.

FIG. 12 is a block diagram schematically showing the configuration of a digital camera according to a third embodiment.

FIG. 13 is a diagram showing an example of an image obtained by pre-shooting for knowing a range illuminated by flash light in the digital camera of the third embodiment.

FIG. 14 is a diagram showing an example of a range in which a drive signal is preferentially given when shooting is performed by emitting flash light in the digital camera of the third embodiment.

FIG. 15 is a diagram showing an example of the order of pixels that give a drive signal when photographing is performed by emitting flash light in the digital camera of the third embodiment.

FIG. 16 is a diagram schematically showing an example of the relationship between the position of a pixel and the photoelectric conversion time when shooting is performed by emitting flash light in the digital camera of the third embodiment.

FIG. 17 is a flowchart showing the flow of a pixel drive control process in shooting with flash light emission in the digital camera of the third embodiment.

FIG. 18 is a flowchart showing the flow of control processing of pixel driving in shooting without flash emission in the digital camera of the third embodiment.

FIG. 19 is a diagram showing the order of pixels to give a drive signal in the digital camera of the fourth embodiment.

FIG. 20 is a diagram showing an example of a relationship between pixel positions and photoelectric conversion timings in the digital camera of the fourth embodiment.

FIG. 21 is a diagram showing a coordinate system on an image sensor.

FIG. 22 is a diagram schematically showing an example of a relationship between pixel positions and photoelectric conversion timing in a conventional digital camera.

23 is a diagram schematically showing the photoelectric conversion timing of pixels of the image sensor in the example of FIG.

24 is a diagram schematically showing the photoelectric conversion time of pixels of the image sensor in the example of FIG.

FIG. 25 is a diagram schematically showing an example of an inappropriate relationship between a photoelectric conversion time and a flash light emission time in a conventional digital camera.

26 is a diagram schematically showing the brightness of the image sensor in the example of FIG. 25 during photoelectric conversion.

FIG. 27 is a diagram schematically showing an example of an appropriate relationship between a photoelectric conversion time and a flash light emission time in a conventional digital camera.

28 is a diagram schematically showing the brightness of the image sensor in the example of FIG. 27 during photoelectric conversion.

[Explanation of symbols]

1, 2, 3, 4 digital camera 11 Shooting lens 12 Image sensor 13 Signal processor 14 Memory 15 Recording section 16 Drive 17 Lens / Aperture drive 18 Lens information detector 19 Operation part 20 Control unit 21 Light source color detector 22 Illuminance distribution storage unit 23 Light emitting part

Continued front page    F-term (reference) 2H053 CA21                 5C022 AA13 AB15 AB17 AC42 AC55                       AC69                 5C024 BX01 CX51 DX01 DX04 GY31                       JX09 JX21 JX36                 5C065 AA03 BB39 BB48 CC01 CC08                       DD15 EE03 FF05 GG14

Claims (9)

[Claims] 1. A charge is generated and accumulated by photoelectric conversion,
An image sensor that has a two-dimensionally arrayed pixel that outputs a signal representing the amount of accumulated charge and that erases accumulated charge and outputs a signal for each pixel individually; An image forming optical system for forming an image is provided, and a first drive signal for instructing erasure of accumulated charges and a second drive signal for instructing signal output are provided to pixels of the image sensor during exposure of the image sensor. In the image pickup apparatus that captures an image by generating image data from the signals output from the pixels of the image pickup element, the order of the pixels providing the second drive signal is different from the order of the two-dimensional array of the pixels. Image pickup device. 2. A second drive signal is given to a pixel located within a range substantially corresponding to a range of a subject to be imaged in which the imaging optical system is in focus, before a pixel located outside the range. The image pickup apparatus according to claim 1, wherein 3. When the flash light is emitted between the time when the first drive signal is applied and the time when the second drive signal is applied,
The second drive signal is applied to a pixel located within a range substantially corresponding to a range of a subject to be illuminated by flash light, prior to a pixel located outside the range. The imaging device described. 4. The image pickup apparatus according to claim 1, wherein a second drive signal is applied to a pixel located in a central portion of the image pickup element prior to a pixel located in a peripheral portion. 5. A charge is generated and accumulated by photoelectric conversion,
An image sensor that has a two-dimensionally arrayed pixel that outputs a signal representing the amount of accumulated charge and that erases accumulated charge and outputs a signal for each pixel individually; An image forming optical system for forming an image is provided, and a first drive signal for instructing erasure of accumulated charges and a second drive signal for instructing signal output are provided to pixels of the image sensor during exposure of the image sensor. Then, in an imaging device that captures an image by generating image data from the signals output from the pixels of the image sensor, the time from the application of the first drive signal to the application of the second drive signal is An imaging device characterized by being different. 6. The time from application of the first drive signal to application of the second drive signal is determined according to the illuminance of each pixel based on the state of the imaging optical system.
The imaging device according to. 7. A pixel of an image sensor includes a plurality of types having different wavelengths of light for photoelectric conversion, and the time from applying a first drive signal to applying a second drive signal is The image pickup apparatus according to claim 5, wherein the image pickup apparatus is determined according to the type of pixel. 8. The method according to claim 7, wherein the time from the application of the first drive signal to the application of the second drive signal is determined according to the color characteristic of the light illuminating the object to be photographed. Imaging device. 9. An electric charge is generated and accumulated by photoelectric conversion,
An image pickup element that has a two-dimensionally arrayed pixel that outputs a signal indicating the amount of accumulated charge and that erases accumulated charge and outputs a signal for each pixel individually; An image forming optical system for forming an image is provided, and a first drive signal for instructing erasure of accumulated charges and a second drive signal for instructing output of a signal are applied to pixels of the image sensor during exposure of the image sensor. Then, in an imaging device that captures an image by generating image data from the signals output from the pixels of the image sensor, the time to give the first drive signal and the time to give the second drive signal are variable for each pixel. An imaging device characterized in that there is.