JP2004320147A - Imaging control method and imaging control apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging control method and an imaging control apparatus capable of reducing a processing time for imaging adjustment for carrying out automatic exposure adjustment and automatic focus adjustment. <P>SOLUTION: The control apparatus drives a solid-state imaging element, wherein high sensitivity pixels with high sensitivities having relatively wide areas and low sensitivity pixels with low sensitivities having relatively narrow areas are formed as a group of pixels and a plurality of the groups of pixels are respectively laid out while being deviated in horizontal and vertical scanning directions by a half of the pixel pitch of the group pixels so as to image an object field by a plurality of frames, and uses imaging signals generated by the high sensitivity pixels and imaging signals generated by the low sensitivity pixels to carry out the automatic exposure adjustment and the automatic focus adjustment in parallel. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an imaging control method and an imaging control apparatus that perform imaging control for imaging an object scene using an imaging signal of the object scene imaged by a solid-state imaging device, and in particular, exposure adjustment and focus adjustment. Are related to an imaging control method and an imaging control apparatus.
[0002]
[Prior art]
In recent years, in a digital camera that captures a scene and stores and outputs a captured image as a digital signal, an imaging lens is used by using a high-frequency component of the imaging signal that is captured and output by a solid-state image sensor. It is equipped with an automatic adjustment function that automatically adjusts the focus of the object scene image formed by, or measures the object scene based on the output level of the imaging signal and determines the exposure value at the time of shooting .
[0003]
For CCD image sensors and CMOS solid-state image sensors, cameras employing high-pixel image sensors each having a large number of pixels constituting an image have been well received. In such an image pickup device, the chip area cannot be simply increased as the number of pixels increases, and therefore the area of the light receiving portion forming the pixels becomes relatively smaller as the number of pixels increases when compared with the same chip area. .
[0004]
On the other hand, there is a demand for more faithful reproduction of the object scene, and in addition to a high-definition image with a high pixel density, it is expected to obtain an image with a wider dynamic range and rich gradation.
[0005]
In actual actual shooting, the above-described automatic adjustment function is used to perform automatic exposure adjustment (AE) first to obtain an appropriate exposure value, and then perform main imaging, and the high frequency of the imaging signal captured with appropriate exposure. Component (contrast component) is calculated for each captured image of the frame taken while moving the imaging lens. The imaging lens is moved to the position where the contrast component is maximized, and an object scene image is formed on the imaging surface of the imaging device. Let In such an imaging adjustment method, in order to support shooting under illuminance conditions from a dark place such as a night view or indoors to a bright place under sunlight, the exposure condition is divided into multiple times during photometry. There was a need. This eliminates the wide dynamic range metering element dedicated to metering, and by using the image sensor in this way, it is possible to accurately perform the metering of various characteristics with appropriate evaluation depending on the situation in the imaging screen. It becomes possible. Further, at the time of automatic focus adjustment (AF), a lens position where high contrast is obtained is determined as an in-focus position based on imaging signals captured at a plurality of positions (AF positions) while changing the position of the imaging lens. Controls focus adjustment.
[0006]
A solid-state imaging device that obtains an image with a wide dynamic range is described in Patent Document 1, for example. In the light receiving elements included in the first light receiving element group of the solid-state imaging device in Patent Document 1, the centers of the geometric shapes of the light receiving elements are aligned with respect to the light receiving elements included in the second light receiving element group. It was a so-called honeycomb arrangement in which the direction and / or the distance corresponding to half the pitch of the light receiving elements were shifted.
[0007]
Patent Document 2 discloses a solid-state imaging device that divides a photodiode portion into two regions and switches a light receiving area by a switching element to perform two-stage sensitivity switching.
[0008]
In Patent Document 3, each light-receiving unit is divided into a plurality of light-receiving regions with different sensitivities, the generated charges of the light-receiving regions with the same sensitivity are mixed and transferred by a vertical transfer register, and signal charges in the light-receiving regions with different sensitivities are transferred. A solid-state imaging device that performs horizontal transfer separately using a horizontal transfer register is disclosed.
[0009]
[Patent Document 1]
JP 2000-125209 A
[Patent Document 2]
Japanese Patent Laid-Open No. 5-207376
[Patent Document 3]
JP-A-9-205589.
[0010]
[Problems to be solved by the invention]
As described above, conventionally, the exposure is adjusted based on the image signal picked up by the exposure in a plurality of stages, and the image is picked up at a plurality of AF positions with the adjusted exposure to obtain a plurality of image signals. It was necessary to go through multiple stages of using autofocusing.
[0011]
When performing photometry for automatic exposure adjustment, a signal generated by the image sensor is obtained by imaging multiple frames by giving the amount of light received by the image sensor to the exposure speed in multiple stages according to the shutter speed and aperture, etc. It is possible to prevent the saturation state of electric charges, determine the luminance state of the object scene based on the signal level of the image signal picked up with a low saturation state, and determine the optimum exposure value at the time of actual imaging In addition, the contrast component of the object scene is extracted based on the imaging signals of a plurality of frames that are newly captured at a plurality of AF positions with the determined exposure value, and based on this, the imaging lens of the imaging lens at the time of actual imaging is extracted. A procedure to control the lens position was required.
[0012]
For this reason, since a lot of time is required for the exposure adjustment and the focus adjustment, there is a problem that the time lag until the actual photographing is performed after performing the imaging adjustment after the shutter release operation is increased. In the above publications 1 to 3, these problems and solutions were not considered.
[0013]
An object of the present invention is to provide an image pickup control method and an image pickup control apparatus capable of eliminating the drawbacks of the prior art and reducing the processing time in image pickup adjustment for performing automatic exposure adjustment and automatic focus adjustment.
[0014]
[Means for Solving the Problems]
In order to solve the above-described problem, the present invention has a main photosensitive portion that forms a first pixel with a relatively large area and high sensitivity, and a relatively small area adjacent to the main photosensitive portion. The sub-photosensitive part that forms the low-sensitivity second pixel is formed as one set pixel, and a plurality of set pixels are horizontally and vertically scanned in the light receiving region on the semiconductor substrate by a half of the pixel pitch of the set pixel. First, a solid-state imaging device is prepared, and the solid-state imaging device is driven to capture an image of the object scene continuously for a plurality of frames, and a first signal corresponding to the signal charge generated by the first pixel is obtained. And the second image signal corresponding to the signal charge generated by the second pixel are read from the solid-state imaging device, and each of the first pixel and the second pixel read in the same frame is read. Using the image signal, including automatic exposure adjustment and automatic focus adjustment. And performing by parallel imaging regulation.
[0015]
In this case, the first image signal may be used for automatic exposure adjustment, and the second image signal may be used for automatic focus adjustment.
[0016]
Further, the first image signal may be read for every other line for the first pixels adjacent in the vertical scanning direction.
[0017]
Further, it is preferable to read the second image signal for every other line for the second pixels adjacent in the vertical scanning direction.
[0018]
Further, after completion of the automatic exposure adjustment and the automatic focus adjustment, the exposure field determined by the automatic exposure adjustment is controlled to image the object scene, and the image signal to be used among the captured image signals is the first pixel. The first image signal is switched to the first image signal, and the focus position is adjusted with higher accuracy than the position adjusted by the automatic focus adjustment using the first image signal.
[0019]
When the focus position is adjusted with high accuracy, reading of the second image signal from the second pixel may be stopped.
[0020]
Further, when the focus position is adjusted with high accuracy, the moving range of the imaging lens may be limited according to the focus position controlled by automatic focus adjustment.
[0021]
In addition, when adjusting the imaging, the exposure condition is changed to switch to a range of a plurality of stages, the object scene is imaged, and the second image from the second pixel among the image signals captured in the different exposure conditions. The level of the signal may be corrected according to the exposure conditions, contrast information for automatic focus adjustment may be calculated based on the corrected second image signal, and the position of the imaging lens may be controlled to a position corresponding to the contrast information.
[0022]
According to another aspect of the present invention, there is provided an imaging control apparatus that performs imaging adjustment including automatic exposure adjustment and automatic focus adjustment in order to solve the above-described problems. An imaging lens that can be moved to control the focus position, a main photosensitive portion that forms a first pixel with a relatively large area and a high sensitivity, and a relatively small area adjacent to the main photosensitive portion. And a sub-photosensitive portion that forms a low-sensitivity second pixel is formed as one set pixel, and a plurality of set pixels are placed in a light receiving region on the semiconductor substrate by a half of the pitch of the set pixels in the horizontal and vertical scanning directions. Output from the solid-state image pickup device, a solid-state image pickup device that is disposed at a distance from each other, shutter means that is disposed between the image pickup lens and the solid-state image pickup device and blocks and releases a light beam incident through the image pickup lens. Processing image signals Signal processing means for controlling, and control means for controlling automatic exposure adjustment and automatic focus adjustment. The control means controls means for driving the solid-state imaging device, means for controlling the exposure amount, and focus of the imaging lens. Means for controlling automatic exposure adjustment based on the first image signal, and performing automatic focus adjustment control based on the second image signal in parallel with the automatic exposure adjustment control. .
[0023]
In this case, after completion of the automatic exposure adjustment and the automatic focus adjustment, the control means controls the exposure value determined by the automatic exposure adjustment to image the scene, and the first image of the captured image signals The focus position may be adjusted with higher accuracy than the position adjusted by the automatic focus adjustment using the signal.
[0024]
In the solid-state imaging device, the light receiving area ratio between the first pixel and the second pixel is preferably 3 to 1 or more.
[0025]
In addition, the solid-state imaging device includes a first image signal corresponding to the signal charge generated in the first pixel and a second image signal corresponding to the signal charge generated in the second pixel. It is good to output each independently.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of an imaging control method and an imaging control apparatus according to the present invention will be described in detail with reference to the accompanying drawings.
[0027]
Referring to FIG. 2, a block diagram of the digital camera in the present embodiment is shown. The digital camera 10 processes an imaging signal of an object imaged by an imaging lens 12, a shutter unit 14 and a solid-state imaging device (CCD) 16. Thus, the imaging apparatus generates image data representing a color image or a monochrome image. The camera 10 captures an object scene, encodes a high-resolution captured image into a storage device such as a memory card by encoding, for example, a still image, automatic exposure adjustment (AE), and automatic focus adjustment. An imaging adjustment mode in which (AF) is performed and a moving image mode in which framing, focus, and the like are confirmed and the captured images are sequentially output are provided.
[0028]
In this embodiment, when the camera 10 is activated, the moving image mode is set, and when the release switch provided in the operation unit 26 is half-pressed and the first stroke (S1) is detected, the mode shifts to the imaging adjustment mode. Thereafter, when the second stroke (S2) is detected by further pressing down, the still image mode is set. In addition, the moving image mode can be manually set and canceled according to the operation, and the exposure and the focus can be arbitrarily adjusted manually.
[0029]
In the imaging adjustment mode, the digital camera 10 performs imaging adjustment such as automatic focus adjustment (AF) and automatic exposure adjustment (AE) based on the output signal of the solid-state imaging device 16 having a plurality of pixels arranged two-dimensionally. . The automatic exposure adjustment function of the camera 10 processes the output signal from the solid-state image sensor 16 in the imaging adjustment mode, measures the brightness level of the object scene based on the processing result, and the shutter speed and the aperture value according to the photometric result. The exposure value (EV) is controlled by the combination. The solid-state image sensor 16 in the present embodiment is an image sensor including a light receiving element in which each pixel formed by a photodiode (PD) is divided into large and small high-sensitivity pixels and low-sensitivity pixels to give a sensitivity difference. is there.
[0030]
The shutter unit 14 disposed between the imaging lens 12 and the solid-state imaging device 16 includes a mechanical shutter that shields the solid-state imaging device 16 and an aperture that adjusts the amount of light. The mechanical shutter starts exposure. Open before and close at the end of exposure to control exposure time, ie shutter speed. In this embodiment, the substantial exposure start timing is performed by electronic shutter control. The stop adjusts the exposure amount by variably limiting the amount of light that enters through the imaging lens 12 and reaches the imaging surface of the solid-state imaging device 16.
[0031]
A lens position (AF position) related to the focus adjustment of the imaging lens 12 is controlled and driven by a driver circuit and a transfer mechanism provided in the lens driving unit 20. The lens driving unit 20 is connected to a central processing unit (CPU) 22 and controls the AF position of the imaging lens 12 according to AF information supplied from the central processing unit 22. Further, the mechanical shutter and the diaphragm are driven by an electromagnetic mechanism provided in the shutter driving unit 24.
[0032]
The operation of the shutter drive unit 24 is controlled at a timing according to the AE information supplied from the timing signal generation circuit (TG) 30 in the signal processing circuit 28 connected to the output 26 of the solid-state imaging device 16. This AE information is also supplied to the vertical driver 32 that drives the solid-state imaging device 16. The vertical driver 32 is a driving circuit that drives scanning of the solid-state imaging device 16 mainly in the vertical direction, and controls the generation of signal charges and the discharge of unnecessary charges in the solid-state imaging device 16 to perform vertical transfer of the generated signal charges. It has an electronic shutter control function that is controlled according to the AE information. The vertical driver 32 has a function of switching the high-sensitivity pixel and the low-sensitivity pixel every other line in the vertical scanning direction of the solid-state image sensor 16 and reading the signal charge, particularly in the imaging adjustment mode. It also has a function of independently performing readout driving of only pixels and readout driving of only low-sensitivity pixels.
[0033]
In addition, the automatic focus adjustment function (AF) of the camera 10 is based on the output signal of the solid-state imaging device 16 so that a desired subject is focused on the imaging surface of the solid-state imaging device 16 via the imaging lens 12. 12 is moved to control the focus. This imaging adjustment function is executed in response to the release operation of pressing the first stroke (S1) by the operator. In order to obtain a still image by detecting the second stroke (S2) of the release switch after the imaging adjustment operation is completed. However, the present invention is not limited to this, and with the shortening of the imaging adjustment processing control, the imaging adjustment and the main imaging operation are sequentially performed with only one press of the release switch. can do.
[0034]
When the digital camera 10 shifts to the still image mode, the digital camera 10 processes one or a plurality of still images to be picked up, compresses and encodes the processed image data, or is attached to a storage device (not shown) without compression. Record on an information recording medium.
[0035]
The digital camera 10 drives a solid-state imaging device 16 having a unique pixel configuration of high-sensitivity pixels and low-sensitivity pixels, and performs automatic focus adjustment (AF) and automatic exposure adjustment (AE) substantially simultaneously. The imaging adjustment time is shortened.
[0036]
Specifically, as shown in FIG. 3, a pixel arrangement on the imaging surface of the solid-state image pickup device 16 and a part of a vertical transfer path (VCCD), the solid-state image pickup device 16 includes high-sensitivity pixels (PD _L ) And a high sensitivity light receiving area having a relatively large light receiving area and a low sensitivity pixel (PD). _S ) With a relatively small light receiving area and a high sensitivity pixel (PD) _L ) And a low-sensitivity small light-receiving area arranged as a partial area of a quadrilateral with a high-sensitivity pixel as a set pixel (PD) by a set of photodiodes, and a set of set pixels (PD) A plurality of honeycombs are arranged in the vertical scanning direction and the horizontal scanning direction so as to be shifted by a half pitch of the set pixel interval. In the embodiment, each high-sensitivity pixel (PD) _L ) And low sensitivity pixels (PD) _S ) Is formed into a quadrilateral shape as a whole, and each side of the quadrilateral is arranged so as to be inclined by approximately 45 degrees with respect to the horizontal and vertical scanning directions. The shape of the set pixel (PD) is not limited to, for example, as shown in FIG. 9, and may be a hexagon or octagon that is a pentagon or more as a whole, and is not limited to a polygon but may be a circle. In the configuration example shown in FIG. 9, the two apex angles of the set pixel (PD) are set to low sensitivity pixels (PD). _S ) Side to include. In addition, as shown in FIG. _L ) And low sensitivity pixels (PD) _S ), Each apex angle of the set pixel (PD) is a low-sensitivity pixel (PD). _S It is good also as the shape which divided the pixel so that it may be included in the side. The area of these pixel divisions is, for example, a high-sensitivity high-sensitivity pixel (PD _L ) And low-sensitivity pixels (PD) _S ) And an area ratio of about 3 to 1 or more, for example, 4 to 1 to 6 to 1, etc., the sensitivity difference necessary for the simultaneous processing of automatic exposure adjustment (AE) and automatic focus adjustment (AF) is reduced. High sensitivity pixel (PD _L ) And low sensitivity pixels (PD) _S ).
[0037]
Referring to FIG. 4, an example of the output signal level with respect to the amount of light incident on the solid-state imaging device 16 is shown. As shown in the figure, when the amount of incident light increases, first the high sensitivity pixel (PD _L The signal charge in) is quickly saturated and the output level after that becomes constant, but the low sensitivity pixel (PD) _S ), The sensitivity is low, so high-sensitivity pixels (PD _L The output level rises after). When the incident light quantity reaches a saturation level, high-sensitivity pixels (PD _L ) Output of low sensitivity pixels (PD _S ) Output can be obtained that can be used for automatic focus adjustment in the range of all input light amounts with a slope in FIG. In this way, high sensitivity pixels (PD _L ), The dynamic range is narrow and it becomes saturated immediately. _S ) Produces an output with a wide dynamic range. Therefore, in this embodiment, the exposure range can be varied by switching the range by dividing the photometry range into four steps of photometry conditions (AE (a) to AE (d)) for an object field with a wide luminance difference. High-sensitivity pixels (PD) set and exposed in multiple stages _L ) For photoexposure and automatic exposure adjustment (AE), and low-sensitivity pixels (PD) that are exposed simultaneously. _S The contrast position for automatic focus adjustment (AF) is calculated using the output from), and the control position of the imaging lens 12 is obtained. High-sensitivity pixel (PD) according to switching of metering conditions _L ) Is shown in FIG. 5, and FIG. 6 shows a low-sensitivity pixel (PD). _S ) Dynamic range.
[0038]
Returning to FIG. 3, RGB primary color filters are arranged in G stripes and R / B checkers in each set pixel (PD) of the solid-state imaging device 16. Microlenses for improving the light receiving rate are arranged on the surface side further above each set pixel (PD) to improve the light collection efficiency. An example of the color arrangement of the color filter is indicated by letters “R”, “G”, and “B” on the high-sensitivity pixel side in FIG. These color filters have high sensitivity pixels (PD). _L ) Is a low-sensitivity pixel (PD) that forms one set pixel (PD) adjacent to _S ) Also have corresponding color component filters. "R" indicates a red component, "G" indicates a green component, and "B" indicates a blue component. The color arrangement is not limited to this embodiment, and for example, a complementary color filter may be used as another color component. In addition, low sensitivity pixel (PD _S ), A G-component color filter with high transmittance is arranged, and a high-sensitivity high-sensitivity pixel (PD) _L ) May be provided with low-transmittance R and B component color filters. In this case, the R and B component high-sensitivity pixels (PD) _L ) Are shifted from each other in the horizontal and vertical scanning directions by a half pixel pitch, which is advantageous in terms of resolution improvement and sensitivity difference compensation.
[0039]
A vertical transfer path (VCCD) for transferring a signal charge generated in each light receiving region in the vertical scanning direction is provided around each set pixel (PD) in the gap between each set pixel (PD) of the solid-state imaging device 16. Are arranged in a zigzag pattern. The vertical transfer path (VCCD) is constituted by a charge coupled device. Each high sensitivity pixel (PD _L ) And each low-sensitivity pixel (PD) _S ), A transfer gate (not shown) is formed at a portion facing the vertical transfer path (VCCD) on the right side of the drawing.
[0040]
The signal charge generated in each pixel is read out via the transfer gate to the right vertical transfer path (VCCD) in response to the shift pulse supplied from the vertical driver 32. A transfer electrode is disposed above the vertical transfer path (VCCD), and a vertical transfer path connected to each pixel via a transfer gate by changing the potential applied to the transfer electrode is, for example, By changing to four potential regions (VCCD (1) to VCCD (4)), the signal charge shifted from each pixel to the vertical transfer path (VCCD) is transferred in the direction of a horizontal transfer path (not shown). In addition, when reading out the low-sensitivity pixel line and reading out the high-sensitivity pixel line separately for each field, potential regions (VCCD (1) to VCCD (4)) adjacent to each set pixel (PD) are set. The potential of the transfer electrode can be controlled so as to form a set of regions, and the potential well can be moved at intervals of each set of pixel units. In this case, since the read pixel interval is widened, the signal charge transfer rate can be further increased.
[0041]
A horizontal transfer path (not shown) is provided at one end of the vertical transfer path (VCCD) in the signal charge transfer direction, and the horizontal transfer path is responsive to a transfer pulse supplied from a horizontal driver 34 in the signal processing circuit 28. Thus, the charge coupled device receives the signal charges transferred from a plurality of vertical transfer paths (VCCD) and transfers the signal charges in the horizontal scanning direction. An output amplifier (not shown) is provided at the transfer destination of the horizontal transfer path, and the signal charge transferred from the horizontal transfer path is read out as an electrical signal corresponding to the amount of the charge and output to the output 26.
[0042]
Thus, these high sensitivity pixels (PD _L ) Light reception signal and low sensitivity pixel (PD) _S ) Can be read out separately and independently in response to a drive signal supplied from the signal processing circuit 28 and the vertical driver 32 to the solid-state imaging device 16. In the imaging adjustment in the present embodiment, the electric signals generated in the respective light receiving regions during the same exposure period and read from the solid-state imaging device 16 are used at almost the same timing for both photometry and focus adjustment, and the photometry processing and focus adjustment are performed. It is performed in parallel with processing.
[0043]
The signal processing circuit 28 includes a correlated double sampling circuit (CDS) 36 connected to the output 26 of the solid-state imaging device 16, an automatic gain variable amplifier circuit (AGC / WB) 38, and an analog / digital conversion circuit (ADC) 40. The output 42 of the ADC 40 is connected to a digital signal processor (DSP) 44. The signal processing circuit 28 further includes the timing signal generation circuit (TG) 30 described above, a horizontal driver 34, and a digital / analog conversion circuit (DAC) 46.
[0044]
The digital signal processing device (DSP) 44 includes a gamma correction / YC processing circuit 50 that performs gamma correction on an input signal and converts it into a YC signal composed of luminance and color difference, and an integration circuit 52, each of which has an input 42. 2 is a signal processor that performs arithmetic processing on a digital image signal input to. As a function unique to the present embodiment, the gamma correction / YC processing circuit 50 includes a high-sensitivity pixel (PD _L ) And low sensitivity pixels (PD) _S ) And a pixel formation processing function that uses these set pixels (PD) as one pixel, and calculates a wide dynamic range value, and calculates the value of each color component at each pixel position. The pixel value of each of the RGB components is calculated. Further, the solid-state imaging device 16 is formed without arranging a color filter in the low-sensitivity pixel portion, and the luminance signal is mainly used as the low-sensitivity pixel (PD). _S Signal processing can also be obtained. The output 54 of the gamma correction / YC processing circuit 50 is connected to, for example, a recording device having a compression encoding circuit or the like, and records the processed image signal on an information storage medium, or the image signal to another device. It is transmitted via a communication channel.
[0045]
The integrating circuit 52 obtains luminance information for each block obtained by dividing the screen into a plurality of blocks by integrating the image signals input in the imaging adjustment mode for each predetermined area in the imaging area. The integrating circuit 52 further has a function of extracting a high-frequency luminance component of the image signal, and generates contrast information used in focus adjustment. The integrating circuit 52 may generate the contrast information by inputting the luminance signal Y generated by the gamma correction / YC processing circuit 50.
[0046]
An output 56 of the integrating circuit 52 is connected to a memory 60. The memory 60 stores input luminance information for each block, and stores input contrast information for each block. The memory 60 has a storage area for storing contrast information for each position generated from image signals captured at a plurality of AF positions of the imaging lens 12. The memory 60 outputs stored information to the output 62 in response to a request from the central processing unit (CPU) 22 connected via the connection line 62.
[0047]
The central processing unit (CPU) 22 is a control circuit that controls the overall operation of the camera 10, and advantageously, an arithmetic circuit that performs arithmetic processing in accordance with a control program, a storage circuit that stores programs and various data, and information It is formed by a computer circuit including an input / output circuit that controls input / output. The central processing unit 22 sets the above-described still image mode, imaging adjustment mode, and moving image mode according to the operation, performs control according to each mode, and generates information necessary for performing the main imaging. .
[0048]
In particular, the central processing unit (CPU) 22 in the imaging adjustment mode performs range exposure by switching to a photometric condition with different exposure values to perform photometry with high accuracy on an object field having a large luminance difference. Have
[0049]
Specifically, the central processing unit (CPU) 22 in the imaging adjustment mode outputs an imaging signal imaged under a photometric condition (a) corresponding to the light amount AE (a) shown in FIG. 5 and then the light amount AE (b). The imaging signal imaged under the corresponding photometric condition (b), the imaging signal imaged under the photometric condition (c) corresponding to the light amount AE (c), and then the photometric condition ( Based on the signal level of the image pickup signal, for example, based on the signal level of the image pickup signal, the image pickup signal picked up in step d) is sequentially used to determine which of the conditions (a) to (d) is appropriate. Judgment is made according to the saturation state. When determining the optimum photometric conditions, the central processing unit 22 determines the exposure value for the subject based on the imaging signal imaged under the photometric conditions, and thereafter controls each unit to image according to the exposure value. .
[0050]
The determination of these photometric conditions and the determination of the exposure value are performed by the high-sensitivity pixel (PD) of the solid-state image sensor 16. _L This is performed using an imaging signal corresponding to the signal charge generated in (1). In the example shown in the figure, when the brightness of a desired main subject is indicated by a point P, the most appropriate photometric processing within the range of the photometric condition (c) within the range of the light amount AE (c) is the photometric process. In the range of photometry conditions (a) and (b) in the range of a) and (b), it is determined that the exposure is overexposed, and in the range of the photometry condition (d) corresponding to the light amount AE (d), it is determined that the exposure is underexposed. . In the embodiment, such a photometric range is switched to determine an appropriate photometric range, and an appropriate photometric range is selected to re-measure the object scene with high accuracy. The metering range is switched by electronic shutter control that controls the closing timing and aperture value of the mechanical shutter with respect to the shutter unit 14, and further controls the start timing of the electronic shutter.
[0051]
Further, the central processing unit 22 uses the other low sensitivity pixel (PD). _S ) To control the focus adjustment using the imaging signal corresponding to the signal charge generated in (1). The low sensitivity pixel (PD) shown in FIG. _S ) Of low-sensitivity pixels (PD) _S Since the image pickup signal from (2) has a wide dynamic range, it is possible to obtain contrast information for performing focus adjustment even when image pickup is performed under all photometric conditions. Note that low-sensitivity pixels (PD _S ), The signal level itself is a low output level. Therefore, the automatic gain variable amplifier circuit (AGC / WB) 38 in the signal processing circuit 28 has a low sensitivity pixel (PD). _S Contrast information is generated using the image signal obtained by performing amplification for sensitivity correction on the image signal from (1).
[0052]
The central processing unit (CPU) 22 determines an AF evaluation value for controlling the in-focus position of the imaging lens 12 based on the contrast information for each block. This AF evaluation value is determined according to conditions such as a photometric mode in which a picture of the object scene and a specific block in the imaging screen are preferentially evaluated. At this time, the central processing unit 22 has a function of correcting the determined AF evaluation value in accordance with each photometric condition (a) to (d) and obtaining an appropriate hill-climbing curve in the object scene.
[0053]
The central processing unit (CPU) 22 reads the high-sensitivity pixel line and the low-sensitivity pixel line in two fields after the exposure to the solid-state imaging device 16 is finished (after the mechanical shutter is closed).
[0054]
Specifically, as shown in FIG. 7, when the central processing unit (CPU) 22 shifts the signal charge of the low-sensitivity pixel line to the vertical transfer path in the imaging adjustment mode, as shown by an arrow in the figure, each of the vertical processing is performed. The low-sensitivity pixels (PD) in the set pixels every other line for the set pixels (PD) arranged in the direction _S ) And high-speed transfer through a vertical transfer path (VCCD). Similarly, when the signal charge of the high-sensitivity pixel line is shifted to the vertical transfer path (VCCD), the central processing unit 22 similarly sets the set pixels (PD) arranged in the vertical scanning direction as indicated by arrows in FIG. High-sensitivity pixels (PD) in every other set of pixels _L ) And high-speed transfer through a vertical transfer path (VCCD). In FIGS. 7 and 8, high sensitivity pixels (PD) are arranged every other line. _L ) And low sensitivity pixels (PD) _S ) Read out signal charge separately High sensitivity pixel (PD _L ) And low sensitivity pixels (PD) _S ), But they are shown separately. _L ) And low sensitivity pixels (PD) _S ) May be shifted to a vertical transfer path (VCCD) separately for each field or read out, or a high-sensitivity pixel (PD) _L ) And low sensitivity pixels (PD) _S Both may be read out by shifting to the vertical transfer path (VCCD) at a time.
[0055]
The automatic exposure adjustment (AE) and the automatic focus adjustment (AF) are simultaneously controlled by using the imaging output based on the signal charges generated by receiving the light with the respective light receiving elements during the same exposure time. Specifically, the digital camera 10 operates according to the flowchart shown in FIG. When the first stroke (S1) of the release switch is detected, the imaging adjustment mode is set, and in step 100, the central processing unit 22 executes automatic exposure adjustment processing and automatic focus adjustment processing by parallel processing.
[0056]
In FIG. 1, the AF position of the imaging lens 12 is focused at a short distance at the timing of the photometric conditions (a) to (d) for each period of the vertical synchronization signal (VD) that defines one frame of one vertical scanning period. High-sensitivity pixels that are controlled to move to a plurality of positions for each vertical scanning period (VD) from the nearest end position where the focal point is in focus to the farthest end (infinity) position that is in focus at a long distance. (PD _L ) And low sensitivity pixels (PD) _S ) Are output from the solid-state imaging device 16.
[0057]
In the example shown in FIG. 1, a state in which an appropriate photometric value is obtained by the photometric condition AE (c) covering the light amount AE (c) corresponding to the brightness P of the subject shown in FIGS. 5 and 6. Show. As shown in FIG. 1, one high-sensitivity pixel (PD) is output using the high-sensitivity pixel output and the low-sensitivity pixel output output in the same vertical scanning period. _L ) Is used for automatic exposure adjustment (AE) and the other low-sensitivity pixel (PD) _S ) Is used for autofocus (AF). In this way, contrast information can be generated as AF information while generating and outputting AE information.
[0058]
In this embodiment, the AF position is described with four lens positions. However, the present invention is not limited to this. For example, the focal length of the imaging lens 12, the depth of field at the time of shooting, the required focus accuracy, and the tolerance Depending on conditions such as the AF speed, the AF position may be set to 8 to 16 points, or the AF position may be set to about 32 points to generate contrast information at each AF position.
[0059]
Low sensitivity pixel (PD _S The level of the imaging signal read out from () is corrected for sensitivity by an automatic gain variable amplifier circuit (AGC / WB) 38, for example, and the central processing unit 22 uses the contrast information calculated by the integrating circuit 52 as each AF position. The AF evaluation value is corrected according to the photometric condition corresponding to. Thereby, for example, as shown in FIG. 12, the AF evaluation values calculated corresponding to the photometric conditions AE (a) to (d) are corrected to the values of AE (a2) to AE (d2), respectively. A hill-climbing curve according to the AF position is obtained.
[0060]
Thus, the exposure is automatically adjusted using the photometric value according to the photometric condition (c), and the position of the imaging lens 12, that is, the AF position is determined based on the maximum AF evaluation value obtained by the hill climbing curve. The aperture, shutter speed, and focus are automatically controlled based on the imaging signal.
[0061]
Returning to FIG. 11, the process proceeds to step 102. When the on state of the second stroke (S2) of the release switch is detected in this state, the still image mode for performing the main imaging is set (step 104). In the still image mode, the solid-state imaging device 16 is exposed with the determined exposure value, and the mechanical shutter is closed when the exposure is completed.
[0062]
Next, when proceeding to Step 106, a high sensitivity pixel (PD) _L ) And low sensitivity pixels (PD) _S ) Are shifted to the vertical transfer path (VCCD) by the transfer gates and further transferred vertically. The signal charges transferred from the plurality of vertical transfer paths (VCCD) are further transferred to the output amplifier side through the horizontal transfer path, and output to the output 26 as an imaging signal from the output amplifier.
[0063]
In step 108, the signal processing circuit 28 performs correlated double sampling on the imaged signal 26, performs signal processing such as adjusting the color balance by amplifying the gain variably, and converting it to a predetermined digital signal by the analog / digital conversion circuit 40. To do. The digitally converted image signal is input to a digital signal processing device (DSP) 44 through a connection line 42 and is subjected to gamma correction by a gamma correction / YC processing circuit 50, and then luminance (Y) and color difference (C Is converted into a YC signal represented by When the converted YC signal is input to a recording device connected to the output 54, the compressed and encoded YC signal is recorded on the storage medium (step 110).
[0064]
Next, referring to FIG. 13, there is shown an embodiment in which automatic focus adjustment (AF) is controlled with higher accuracy in the imaging adjustment mode. In this embodiment, as described in the first embodiment shown in FIG. _S In the second embodiment, the image pickup signal used for further narrowing down the AF position where the in-focus is obtained is used as a high-sensitivity pixel (PD). _L ) To adjust the focus with higher accuracy.
[0065]
The digital camera 10 according to the second embodiment has a configuration similar to that of the block diagram shown in FIG. 2 and further includes an automatic focus adjustment (AF) for narrowing down the AF position as described above to the central processing unit (CPU) 22. Has additional features for. The configuration of the pixel array of the solid-state imaging device 16 provided in the camera 10 may be the same as that of the first embodiment shown in FIG.
[0066]
Specifically, the central processing unit (CPU) 22 controls the exposure value by automatic exposure adjustment (AE) when the photometry is confirmed in the imaging adjustment mode, and the low sensitivity pixel (PD). _S ) Is used to perform auto focus adjustment (AF) in the second stage. The central processing unit 22 switches the driving of the solid-state imaging device 16 so that the low-sensitivity pixel output that has been used for automatic focus adjustment is switched to the high-sensitivity pixel output. In this case, the central processing unit 22 uses low-sensitivity pixels (PD _S ) Reading is stopped, and high-sensitivity pixels (PD) _L ) By controlling the vertical driver 32 and the signal processing circuit 28 so as to read out only the imaging signal corresponding to) from the solid-state imaging device 16. _L ) Can be output from the solid-state imaging device 16 at high speed.
[0067]
In addition, the central processing unit (CPU) 22 has a narrower focus movement range (AF search range) of the imaging lens 12 than a range in which the focus position is moved during automatic focus adjustment (AF) using low-sensitivity pixels. The contrast information can be calculated using the imaging signal captured within the moving range, and the maximum AF evaluation value can be narrowed down with high accuracy. In this case, the low sensitivity pixel (PD _S ) Using a high-sensitivity pixel (PD) in a predetermined range in the back-and-forth movement centered on the lens position adjusted by the first-stage automatic focus adjustment (AF). _L The range of the AF position to which the imaging lens 12 is moved at the time of the second focus adjustment using the imaging signal from () is good.
[0068]
This is shown in FIG. As shown in the figure, the low sensitivity pixel (PD _S ) The AF evaluation value at each AF position (AE / AF (a) to AE / AF (d)) calculated using the image pickup signal from) is predicted at a rough interval and predicted. The lens position corresponding to the range in which the maximum value can be obtained is set to a predetermined width, and in this embodiment, after automatic exposure adjustment (AE), an AF search for moving the imaging lens 12 within the set predetermined width is further performed, and the imaging is performed. High-sensitivity pixels (PD) captured in multiple frames during movement of the lens 12 _L ) To calculate AF evaluation values (AF (e) to AF (h)) at the AF positions. The fine AF evaluation value peak is narrowed down using these further AF evaluation values (AF (e) to AF (h)), and can be adjusted to a more accurate in-focus position. Therefore, at the time of the second-stage automatic focus adjustment using the high-sensitivity pixel output, the AF search from the nearest end to the farthest end (infinite position) is not necessarily performed, and the focus is adjusted to a more accurate position. Therefore, high speed and high accuracy are realized.
[0069]
In this case, a high sensitivity pixel (PD _L ) As well as low-sensitivity pixels (PD) _S The vertical driver 32 and the horizontal driver 34 are controlled so that each set pixel (PD) is thinned and read out in units of a set of pixel sets including the), and contrast information by the set pixel (PD) is calculated. it can.
[0070]
【The invention's effect】
As described above, according to the present invention, the automatic exposure adjustment (AE) and the automatic focus adjustment (AF) are simultaneously performed by using the respective imaging outputs of the high sensitivity pixel and the low sensitivity pixel each having a sensitivity difference. For example, the shutter time lag can be shortened. In addition, more precise imaging adjustment can be performed at the next stage of the imaging adjustment shortened in this way. In this case, the focus can be adjusted with high accuracy, particularly in the second-stage automatic focus adjustment (AF). In this case, furthermore, the movement range of the imaging lens is limited to the vicinity of the control position in the first stage of automatic focus adjustment (AF), and the time required for focus adjustment is further shortened when performing highly accurate focus adjustment. be able to.
[Brief description of the drawings]
FIG. 1 is a timing diagram showing imaging outputs from high-sensitivity pixels and low-sensitivity pixels of a solid-state image sensor and auto focus adjustment (AF) states that change for each photometric condition in an embodiment of a digital camera to which the present invention is applied. It is a chart.
FIG. 2 is a block diagram showing an embodiment of a digital camera to which the present invention is applied.
FIG. 3 is a diagram illustrating a part of a pixel array and a vertical transfer path of a solid-state imaging device in an embodiment.
FIG. 4 is a diagram illustrating output levels according to input light amounts of high-sensitivity pixels and low-sensitivity pixels of a solid-state image sensor.
FIG. 5 is a diagram illustrating a dynamic range of a high-sensitivity pixel according to photometry conditions AE (a) to (d) of the solid-state imaging device.
FIG. 6 is a diagram illustrating a dynamic range of a low sensitivity pixel of a solid-state image sensor.
FIG. 7 is a diagram illustrating a readout state of a low-sensitivity pixel line of the solid-state imaging device.
FIG. 8 is a diagram illustrating a read state of a high-sensitivity pixel line of a solid-state image sensor.
FIG. 9 is a diagram illustrating another configuration example of the high-sensitivity pixel shape and the low-sensitivity pixel shape of the solid-state imaging device.
FIG. 10 is a diagram illustrating still another configuration example of a high-sensitivity pixel shape and a low-sensitivity pixel shape of a solid-state imaging device.
FIG. 11 is a flowchart showing the operation of the digital camera in the embodiment.
FIG. 12 is a diagram illustrating an AF evaluation value corresponding to an AF position of the digital camera and its hill-climbing curve in the embodiment.
FIG. 13 is a timing chart showing imaging outputs from high-sensitivity pixels and low-sensitivity pixels of a solid-state imaging device and exposure control and adjustment operations that change for each photometric condition in another embodiment to which the present invention is applied. .
14 is a diagram showing an AF evaluation value corresponding to an AF position of a digital camera and its hill-climbing curve in another embodiment shown in FIG.
[Explanation of symbols]
10 Digital camera
12 Imaging lens
14 Shutter unit
22 Central processing unit (CPU)
28 Signal processing circuit
44 Digital signal processor (DSP)
52 Integration circuit
60 memory
PD photodiode
PD _L High sensitivity pixel
PD _S Low sensitivity pixel
VCCD vertical transfer path

Claims (12)

A main photosensitive portion having a relatively large area and forming a high-sensitivity first pixel, and a sub-photosensitive portion adjacent to the main photosensitive portion and forming a relatively small area and a low-sensitivity second pixel. A solid-state imaging device in which a photosensitive portion is formed as one set pixel, and a plurality of set pixels are arranged in the light receiving region on the semiconductor substrate by being shifted in the horizontal and vertical scanning directions by a half of the pixel pitch of the set pixel, respectively. Prepare
Drive the solid-state imaging device to continuously image the scene for a plurality of frames,
A first image signal corresponding to the signal charge generated in the first pixel and a second image signal corresponding to the signal charge generated in the second pixel are read from the solid-state imaging device. ,
An imaging control method characterized by performing imaging adjustment including automatic exposure adjustment and automatic focus adjustment in parallel using image signals of the first pixel and the second pixel read out in the same frame. 2. The imaging control method according to claim 1, wherein the first image signal is used for the automatic exposure adjustment, and the second image signal is used for the automatic focus adjustment. . The imaging control method according to claim 1, wherein the method reads out the first image signal for every other line for the first pixels adjacent in the vertical scanning direction. The imaging control method according to claim 1, wherein the method reads out the second image signal for every other line for the second pixels adjacent in the vertical scanning direction. The imaging control method according to claim 1, further comprising: after completion of the automatic exposure adjustment and the automatic focus adjustment.
Control the exposure value determined by the automatic exposure adjustment to image the object scene,
Among the captured image signals, the image signal to be used is switched to the first image signal from the first pixel, and is higher than the position adjusted by the automatic focus adjustment using the first image signal. An imaging control method characterized by matching a focus position with accuracy. 6. The imaging control method according to claim 5, wherein the method stops reading of the second image signal from the second pixel when the focus position is adjusted with high accuracy. Control method. 6. The imaging control method according to claim 5, wherein the method limits the movement range of the imaging lens according to the focus position controlled by the automatic focus adjustment when the focus position is adjusted with high accuracy. A characteristic imaging control method. The imaging control method according to claim 1, wherein the method includes:
When adjusting the imaging, the exposure condition is changed to switch to a multi-stage range to image the scene.
Of the image signals captured under different exposure conditions, the second image signal from the second pixel is level-corrected according to the exposure condition, and the automatic operation is performed based on the corrected second image signal. An imaging control method characterized by calculating contrast information for focus adjustment and controlling the position of the imaging lens to a position corresponding to the contrast information. In an imaging control apparatus that performs imaging adjustment including automatic exposure adjustment and automatic focus adjustment, the apparatus includes:
An imaging lens capable of controlling the focus position by moving in the front-rear direction with respect to the object field in order to perform the automatic focus adjustment;
A main photosensitive portion that forms a high-sensitivity first pixel having a relatively large area and a sub-photosensitive layer that forms a low-sensitivity second pixel having a relatively small area adjacent to the main photosensitive portion. A solid-state imaging device in which a plurality of set pixels are arranged in the light receiving region on the semiconductor substrate while being shifted by a half of the pitch of the set pixels in the horizontal and vertical scanning directions, respectively,
Shutter means disposed between the imaging lens and the solid-state imaging device and configured to shield and open a light beam incident through the imaging lens;
Signal processing means for processing an image signal output from the solid-state imaging device;
Control means for controlling the automatic exposure adjustment and the automatic focus adjustment,
The control means includes means for driving the solid-state imaging device, means for controlling an exposure amount, and means for controlling the focus of the imaging lens, and performs the automatic exposure adjustment based on the first image signal. An image pickup control apparatus that performs control and controls the automatic focus adjustment based on the second image signal in parallel with the automatic exposure adjustment control. 10. The imaging control apparatus according to claim 9, wherein the control unit further controls the exposure value determined by the automatic exposure adjustment to capture an object scene after completion of the automatic exposure adjustment and the automatic focus adjustment. An image pickup control apparatus, wherein the focus position is adjusted with higher accuracy than the position adjusted by the automatic focus adjustment using the first image signal among the picked up image signals. The imaging control device according to claim 9, wherein the solid-state imaging device has a light receiving area ratio of the first pixel and the second pixel of 3 to 1 or more. 10. The imaging control device according to claim 9, wherein the solid-state imaging device includes a first image signal corresponding to a signal charge generated by the first pixel and a signal generated by the second pixel. An imaging control apparatus, wherein a second image signal corresponding to an electric charge is output independently.

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