JP4869474B2 - Imaging device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an imaging apparatus, and more particularly to an imaging apparatus capable of reproducing an image having a substantially wide dynamic range.
[0002]
[Prior art]
A digital still camera generates an image by converting light imaged on a solid-state image sensor through a lens into an electric signal. Currently, a high resolution image is generated by increasing the number of pixels. On the other hand, the dynamic range (DR) of the element itself is very narrow, so that the resulting image is latitude (bright to dark). There is a problem that the reproduction range up to the portion becomes narrow.
[0003]
In order to solve this problem, a method of generating an image having a wide dynamic range by synthesizing images obtained by performing an imaging operation a plurality of times with different exposure amounts is known. However, for example, in the case of shooting a scene with a wide dynamic range in a backlight state (mixed with a dark main subject (person) and a bright background) as shown in FIG. Depending on the shooting scene, as shown in FIGS. 12B and 12C, it is necessary to control the shooting so that the main subject and the background are appropriately exposed.
[0004]
Therefore, what is important is an automatic exposure setting (AE) function for controlling an imaging system (aperture, shutter speed, etc.) of a digital still camera from a shooting scene. For example, Japanese Patent Application Laid-Open No. 7-298142 describes a method of outputting a timing signal related to imaging system control for each of a dark part and a bright part from luminance information of an image of a photographic scene.
[0005]
[Problems to be solved by the invention]
However, in the conventional AE function, in order to control the imaging system so as to obtain an image with good reproducibility, it is necessary to always read information regarding the scene, resulting in a problem that the power consumption increases. Furthermore, when shooting multiple times with different exposures as in the above conventional example, it is necessary to read each information of the bright part and the dark part separately and control both so that they are always appropriate. There is a concern that the amount of power consumption will further increase in comparison with.
[0006]
As a countermeasure for reducing the burden on the AE function, there is a method in which either the main subject or the background is controlled by the AE function, and the exposure ratio between the captured images is separately fixed and the other exposure is adjusted. Conceivable. If the exposure ratio is fixed in this way, the AE function can be configured in the same manner as a general digital still camera.
[0007]
However, there are various cases even in a backlit state where the main subject and the background are clearly separated, and shooting may fail if the brightness changes gently between the two. In addition, when the difference in brightness between a dark indoor and a bright outdoor is very large, it may not be reproduced with an exposure ratio that is within an allowable range with normal backlight.
[0008]
Furthermore, although a method for allowing the user to specify the exposure time and the exposure ratio in the above method is also conceivable, it is difficult for the user side to determine an appropriate exposure time or exposure ratio according to the light / dark difference, and to some extent. Without experience and knowledge of this, it is difficult to determine which exposure time or exposure ratio is optimal, so it is not very practical.
[0009]
Therefore, an object of the present invention made in view of such a point is that an image having a wide dynamic range can be taken even in a shooting scene with a large contrast between light and dark without always driving the AE function. An object of the present invention is to provide an imaging device that can be reproduced.
[0012]
the above Achieve purpose Claim 1 The invention of the imaging apparatus according to
Information acquisition means for acquiring information related to the dynamic range of the shooting scene under a plurality of exposure conditions prior to the main shooting;
Information synthesizing means for synthesizing information on the dynamic range acquired by the information acquiring means;
Histogram calculating means for calculating a histogram of the combined information combined by the information combining means;
Gradation conversion characteristic calculation means for calculating gradation conversion characteristics based on information on the histogram calculated by the histogram calculation means;
Photographing means for performing actual photographing based on the gradation conversion characteristic calculated by the gradation conversion characteristic calculating means;
It is characterized by having.
[0013]
Claim 1 According to the invention, since information on the dynamic range of the photographic scene is acquired based on a plurality of exposure conditions, it is possible to simultaneously acquire information on a dark part and a bright part of the photographic scene and handle them equally. Further, since the combined information is generated by combining the acquired information and the gradation conversion characteristic is calculated from the histogram of the combined information, the gradation conversion characteristic suitable for the shooting scene can be obtained. In addition, since the main shooting is performed based on the calculated gradation conversion characteristics, it is possible to perform shooting suitable for any scene regardless of the dynamic range of the shooting scene. Furthermore, since the image signal in the actual shooting is converted based on the tone conversion characteristics calculated in advance, it is possible to reproduce an image suitable for the shooting scene, and in the image processing for the actual shooting, the tone conversion is performed. Since it is not necessary to obtain the characteristics, the image processing for the actual photographing can be performed easily and quickly.
[0014]
Claim 2 The invention according to Claim 1 In the imaging apparatus described in
The photographing means includes
The image forming apparatus further includes shooting control information calculation means for calculating shooting control information for performing actual shooting based on the tone conversion characteristics calculated by the tone conversion characteristic calculation means.
[0015]
Claim 2 According to the invention, since the shooting control information is calculated using the gradation conversion characteristic calculated based on the information regarding the dynamic range of the shooting scene and the main shooting is performed, that is, the shooting is controlled according to the shooting scene. Therefore, it is possible to shoot in any scene regardless of the dynamic range of the shooting scene.
[0016]
Claim 3 The invention according to Claim 1 or 2 In the imaging apparatus described in
The information relating to the dynamic range acquired by the information acquisition means is luminance information relating to the shooting scene.
[0017]
Claim 3 According to the invention, it is possible to simplify the versatility and configuration of each process by using the luminance information of the shooting scene.
[0018]
Claim 4 The invention according to Claim 2 In the imaging apparatus described in
The shooting control information calculated by the shooting control information calculation means is information for driving the shutter.
[0019]
Claim 4 According to the invention, it is possible to perform shooting with exposure adjusted to a dark part or a bright part of a shooting scene by driving a shutter as control of shooting.
[0020]
Claim 5 The invention according to Claim 2 or 4 In the imaging apparatus described in
The photographing means has a flash light emitting means for irradiating light to a photographing scene, and is configured to control the flash light emitting means based on the photographing control information calculated by the photographing control information calculating means. Is.
[0021]
Claim 5 According to the invention according to the present invention, control is performed so that light is appropriately emitted according to the shooting scene based on the shooting control information even when external flash emission is required for shooting a scene with a high degree of backlight or a night scene. It becomes possible to do.
[0022]
Claim 6 The invention according to Claim 2, 4 or 5 In the imaging apparatus described in
The image pickup device includes information processing means for performing multiple shootings based on the shooting control information and combining image signals of a plurality of images obtained by the multiple shootings. .
[0023]
Claim 6 According to the invention according to the above, it is possible to obtain an image with a wide dynamic range adapted to the shooting scene.
[0024]
Claim 7 The invention according to Claim 1 or 2 In the described imaging apparatus,
The gradation conversion characteristic calculating means calculates a gradation conversion characteristic based on a histogram having a frequency equal to or higher than a predetermined value among the histograms calculated by the histogram calculating means.
[0025]
Claim 7 According to the invention, since the gradation conversion characteristic is calculated using a portion where the frequency of the histogram is equal to or greater than a predetermined value (a portion from which noise or the like is excluded), the gradation conversion characteristic that is suitable for a shooting scene and that suppresses the influence of noise. Can be obtained.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of an imaging apparatus according to the present invention will be described with reference to FIGS.
[0027]
1 to 7 show a first embodiment. FIG. 1 is a block diagram showing an overall schematic configuration of a digital still camera as an image pickup apparatus. FIG. 2 shows an example of a shutter timing control circuit shown in FIG. FIG. 3 is a flowchart showing the operation in the shooting scene adaptive shooting mode, FIGS. 4A and 4B show an example of the shooting scene and its brightness distribution, and FIG. 5 shows the pre-shooting. FIG. 6 is a diagram for explaining the operation, FIG. 6 is a diagram for explaining the peak value detection operation of the histogram, and FIG. 7 is a diagram for explaining the operation of calculating the shutter timing signal from the peak value of the histogram.
[0028]
The digital still camera shown in FIG. 1 uses a single-plate color CCD image pickup device 1 having an electronic shutter function. A subject image is formed on the CCD image pickup device 1 through a lens 2 and an aperture / shutter mechanism 3. The subject image is photoelectrically converted and output as an image signal. The image signal of the subject image from the CCD image pickup device 1 is amplified by the amplifier 4 after being removed by a correlated double sampling circuit or the like (not shown) and further converted into a digital signal by the A / D converter 5. It is supplied to the camera signal processing circuit 6 where it is processed as image data.
[0029]
The output of the A / D converter 5 is also supplied to the AF, AE, AWB detection circuit 7 and the shutter timing control circuit 8. In the AF, AE, AWB detection circuit 7, an AF detection process for extracting AF information for automatically controlling the focus prior to the main photographing, an AE detection process for extracting AE information for automatically controlling the exposure, and AWB detection processing for extracting AWB information for automatically setting the white balance is performed. These AF information, AE information, and AWB information are supplied to the lens 2, the aperture / shutter mechanism 3 and the camera signal processing circuit 6 through the CPU 9, respectively, and in the normal shooting mode, the CPU 9 performs shutter timing based on the AE information. A signal is calculated and supplied to the selection switch 10.
[0030]
In the shutter timing control circuit 8, under the control of the CPU 9, shooting control information for performing actual shooting in the shooting scene adaptive shooting mode, that is, a shutter timing signal in the present embodiment, is calculated. It is supplied to the selection switch 10 and the CPU 9.
[0031]
The camera signal processing circuit 6 and the CPU 9 are connected to a bus line 11, and a DRAM 13 used as a working memory when performing color processing of image data or the like is connected to the bus line 11 via a memory controller 12. In addition, a compression circuit (JPEG) 14 for compressing image data from the camera signal processing circuit 6 is connected. In addition, a memory card I / F 16 is connected to the bus line 11 in order to record the image data compressed by the compression circuit 14 in the memory card 15, and the image data recorded in the memory card 15 is A liquid crystal display element (LCD) 18 is connected via a display circuit 17 in order to read and display or to display a photographing state. Furthermore, a PCI / F 20 for transferring image data recorded on the memory card 15 to a personal computer (PC) 19 is connected to the bus line 11.
[0032]
Further, the CPU 9 sets the flash device 21 controlled based on the AE information from the AF, AE, AWB detection circuit 7 or the shutter timing signal from the shutter timing control circuit 8 according to the shooting mode, and various shooting modes. Input key 22 for driving the trigger switch and the like, and a plurality of different shutter timing signals for acquiring information related to the dynamic range of the shooting scene under different exposure conditions by pre-shooting prior to the main shooting in the shooting scene adaptive shooting mode. In this embodiment, a shutter timing ROM 23 for storing three shutter timing signals ST1, ST2, ST3 is connected. The shutter timing signals ST1, ST2 and ST3 are, for example, ST1 = 1/30 sec, ST2 = 1/500 sec, ST3 = 1/8000 sec.
[0033]
Under the control of the CPU 9, the selection switch 10 selects the shutter timing signal calculated by the CPU 9 based on the AE information in the normal shooting mode and supplies it to the timing generator (TG) 24. In the shooting scene adaptive shooting mode, The shutter timing signal calculated by the shutter timing control circuit 8 is selected and supplied to the TG 24. During the actual photographing, the shutter timing signal from the shutter timing control circuit 8 is selected and supplied to the TG 24. This selection switch The electronic shutter function of the CCD image pickup device 1 is controlled by the TG 24 based on the shutter timing signal selected in 10.
[0034]
In the imaging apparatus shown in FIG. 1, a normal shooting mode in which image synthesis is not performed and a shooting scene adaptive shooting mode in which image synthesis is performed as necessary are manually selected by operating the input keys 22 or CCD imaging is performed. The CPU 9 detects overexposure of the image signal from the element 1 based on the output from the AF, AE, AWB detection circuit 7 and automatically selects it, and the CPU 9 controls the shooting operation according to the selected shooting mode. .
[0035]
That is, when the normal shooting mode is selected, a shooting scene is shot once by a normal shooting operation to obtain an image signal for one screen from the CCD image pickup device 1, and the image signal is received by the camera signal processing circuit 6. To process. When the photographing scene adaptive photographing mode is selected, the photographing scene is pre-photographed three times with the three shutter timing signals ST1, ST2 and ST3 stored in the shutter timing ROM 23 and exposed from the CCD image sensor 1. Acquire information on the dynamic range for three different screens, set the shutter timing signal for the main shooting based on the acquired information on the dynamic range, perform the main shooting, and obtain the image signal obtained by the main shooting. Processing is performed by the camera signal processing circuit 6.
[0036]
FIG. 2 is a block diagram showing a configuration of an example of the shutter timing control circuit 8 shown in FIG. The shutter timing control circuit 8 includes a switch 31, a signal synthesis circuit 32, a signal distribution calculation circuit 33, a signal distribution analysis circuit 34, a shutter timing calculation circuit 35, and a shutter timing calculation lookup table (LUT) 36. Yes.
[0037]
The switch 31 is controlled by the CPU 9 so as to be turned on only during pre-shooting in the shooting scene adaptive shooting mode, whereby each image obtained by sequentially shooting shooting scenes with the shutter timing signals ST1, ST2, ST3 in pre-shooting. A signal (luminance signal) is supplied to the signal synthesis circuit 32 via the A / D converter 5. The signal synthesis circuit 32 synthesizes the input three-screen image signals according to the exposure level at the time of shooting to generate luminance information of a wide dynamic range, and supplies the luminance information to the signal distribution calculation circuit 33.
[0038]
The signal distribution calculation circuit 33 calculates a histogram representing the luminance distribution of the photographic scene based on the input wide dynamic range luminance information, and supplies the calculation result to the signal distribution analysis circuit 34. The signal distribution analysis circuit 34 detects the luminance of the peak value from the input histogram and supplies the luminance information to the shutter timing calculation circuit 35. If there are a plurality of peak values in the histogram, the brightness of each peak value is detected.
[0039]
The shutter timing calculation circuit 35 reads the corresponding shutter timing signal from the shutter timing calculation LUT 36 based on the input luminance information, supplies the read shutter timing signal to the TG 24, and is proportional to the time of the shutter timing signal. Then, in order to control the amount of light emitted from the strobe, it is supplied to the CPU 9 for strobe control and actual photographing is performed. The shutter timing calculation LUT 36 stores a shutter timing signal for appropriate exposure corresponding to the luminance.
[0040]
Hereinafter, the operation in the shooting scene adaptive shooting mode will be described in more detail with reference to FIGS.
[0041]
FIG. 3 is a flowchart showing the operation in the shooting scene adaptive shooting mode. In the shooting scene adaptive shooting mode, first, shutter timing signals ST1, ST2 and ST3 are read from the shutter timing ROM 23 (step S1), and the TG 24 is driven based on the shutter timing signals ST1, ST2 and ST3 to perform pre-shooting ( Step S2), thereby obtaining three-screen image signals (luminance signals) by different exposures (step S3). Note that the pre-photographing in step S2 is performed, for example, by half-pressing the release.
[0042]
When the pre-photographing is completed, as described above, the signal synthesis circuit 32 synthesizes the luminance signal of each image in accordance with the exposure level at the time of pre-photographing to calculate luminance information of a wide dynamic range (step S4).
[0043]
Here, as shown in FIG. 4 (a), the shooting scene has a brightness distribution as shown in FIG. 4 (b) in a backlit state in which a person portion that is a dark main subject and a bright background portion are mixed. In this case, pre-shooting is performed with the shutter timing signals ST1, ST2, and ST3, and the luminance information in each shutter timing signal is matched with the exposure level at the time of pre-shooting, the shooting scene information as shown in FIG. 5 is obtained. Therefore, if these pieces of luminance information are combined in step S4 so as to be weighted and added according to the brightness level in the overlapping portion, luminance information with a wide dynamic range can be obtained.
[0044]
For example, when the luminance information obtained by pre-photographing with each shutter timing signal is represented by 8 bits, the shutter timing signals ST1, ST2 so that the overlapping portion of the luminance information obtained by the adjacent shutter timing signal becomes 2 bits. , ST3, 20 bits (about 120 dB) of information can be obtained.
[0045]
Moreover, in reality, a shooting scene having a large difference in brightness so that the luminance information is represented by 20 bits is exceptional. For example, if the overlapping portion is 4 bits, information of 16 bits (about 96 dB) can be obtained. Can do. In this case, the time ratio between adjacent shutter timing signals is 1:16 because 4 bits of 8 bits are overlapped. For example, ST1 = 1/30 sec, ST2 = 1/500 sec, ST3 as described above. = 1/8000 sec. In this way, the combined luminance signal Y is Y = Y1 + 16 × Y2 + 16 × 16 × Y3, where Y1, Y2 and Y3 are the luminance signals obtained from the shutter timing signals ST1, ST2 and ST3.
[0046]
In FIG. 3, after the luminance information of the wide dynamic range is calculated as described above in step S4, the histogram based on the brightness level is calculated by the signal distribution calculation circuit 33 based on the luminance information (step S5). . The histogram calculated here is, for example, as shown by a curve in FIG. 6 when the shooting scene is FIG.
[0047]
Next, from the histogram calculated in step S5, the signal distribution analysis circuit 34 detects a peak portion and obtains its luminance (step S6). In step S6, for example, a peak detection interval of the histogram is set in advance, a portion where the slope of the histogram frequency value (values at both ends) in the peak detection interval changes from positive to negative is detected as a peak value, and the luminance is determined. Ask. Thereby, in the case of the histogram of FIG. 6, the frequency of the portion indicated by the oblique line of the person portion is detected as a peak value, and the luminance is obtained. In addition, regarding the part where the front and back inclination hardly changes (the part where the slope of the histogram frequency value changes negatively through the part where the inclination of the histogram frequency value hardly changes), it is determined that the part is forming a peak. It detects as a value and obtains its luminance. As a result, in the case of the histogram of FIG. 6, adjacent frequency portions indicated by diagonal lines in the background portion are detected as peak values, and the luminance is obtained. Therefore, when the shooting scene is shown in FIG. 4A, two peak values of the histogram are detected, and the respective luminances are obtained.
[0048]
Note that the peak value of the histogram is used to determine the shooting timing at which the corresponding luminance portion has a relatively appropriate exposure area. As shown in FIG. 6, the shaded portion of the background portion is detected as the peak value. However, since the luminance of the portion does not change extremely and enters one exposure area, it is not always necessary to detect it precisely. Therefore, the signal distribution analysis circuit 34 can be configured easily.
[0049]
When the luminance of the peak value of the histogram is obtained in step S6, the shutter timing calculation circuit 35 calculates a shutter timing signal corresponding to the luminance from the shutter timing calculation LUT 36 as shown in FIG. 7 (step S7). The shutter timing signal thus set is set as the shutter timing signal in the main shooting (step S8), and the main shooting is performed, for example, by pressing the release (step S9).
[0050]
As a result, when the shooting scene is FIG. 4A, image signals for two screens having different exposure amounts at 1/60 sec and 1/500 sec shown in FIG. 7 are obtained in the main shooting. The image signals for the two screens obtained by the actual photographing are combined in the camera signal processing circuit 6 by a known method, whereby an image having a wide dynamic range adapted to the photographing scene can be obtained.
[0051]
As described above, according to the present embodiment, in the shooting scene adaptive shooting mode, the shooting scene is pre-shot with the preset shutter timing signals ST1, ST2, and ST3 to acquire information on the dynamic range, and the combined information Since the main shooting is performed by setting the shutter timing signal in which the luminance portion corresponding to the peak value is a relatively appropriate exposure area, the AE function is always used even in a shooting scene with a large contrast. It is possible to perform shooting suitable for a shooting scene without driving the, and to reproduce an image with a wide dynamic range.
[0052]
FIGS. 8 to 11 show a second embodiment. FIG. 8 is a block diagram showing an overall schematic configuration of a digital still camera as an imaging apparatus. FIG. 9 is a shutter timing control / gradation calculation shown in FIG. FIG. 10A and FIG. 10B are diagrams for explaining the calculation operation of the gradation conversion characteristics, and FIG. 11 shows the operation of calculating the shutter timing signal from the gradation conversion characteristics. It is a figure for demonstrating.
[0053]
The digital still camera of the present embodiment is provided with a shutter timing control / gradation calculation circuit 38 instead of the shutter timing control circuit 8 shown in FIG. 1, and the other configurations are the same as those in FIG. Components having the same action are denoted by the same reference numerals and description thereof is omitted.
[0054]
As shown in FIG. 9, the shutter timing control / gradation calculation circuit 38 includes a switch 41, a signal synthesis circuit 42, a signal distribution calculation circuit 43, a gradation conversion characteristic calculation circuit 44, a shutter timing calculation circuit 45, and a shutter timing calculation. LUT 46 for use.
[0055]
In this embodiment, as in the first embodiment, in the shooting scene adaptive shooting mode, the CPU 9 controls the switch 41 so that it is turned on only during pre-shooting, and shutter timing signals ST1, ST2, and so on in pre-shooting. Each image signal (luminance signal) of the shooting scene obtained by sequentially shooting in ST3 is supplied to the signal synthesis circuit 42 via the A / D converter 5, where the three-screen image signal is set to the exposure level at the time of shooting. The luminance information of a wide dynamic range is generated by combining them, and the luminance information is supplied to the signal distribution calculation circuit 43 to calculate a histogram representing the luminance distribution of the shooting scene.
[0056]
The histogram calculated by the signal distribution calculation circuit 43 is supplied to the gradation conversion characteristic calculation circuit 44, where the gradation conversion characteristic is calculated based on the input histogram. In the present embodiment, a cumulative histogram obtained by removing a noise or the like as shown in FIG. 10B by accumulating a histogram having a frequency equal to or higher than a predetermined threshold from the input histogram as shown in FIG. The cumulative histogram is supplied to the camera signal processing circuit 6 as a gradation conversion characteristic so as to be used for the conversion processing of the image signal obtained by the actual photographing, and is also supplied to the shutter timing calculation circuit 45.
[0057]
The shutter timing calculation circuit 45 reads the corresponding shutter timing signal from the shutter timing calculation LUT 46 based on the input gradation conversion characteristics, supplies the read shutter timing signal to the TG 24, and the first embodiment. Similarly, this is supplied to the CPU 9 for strobe control to perform actual photographing. The shutter timing calculation LUT 46 stores a shutter timing signal for appropriate exposure corresponding to the luminance, as in the first embodiment.
[0058]
Here, when setting the shutter timing signal for the actual photographing from the gradation conversion characteristics, as shown in FIG. 11, the area surrounded by the gradation conversion characteristics with a predetermined value or less, that is, the area with the inclination ( Area where image data exists), and the average value of the luminance obtained by weighting the frequency of the cumulative histogram in the detection area or simply the center value of the luminance range in the detection area is obtained, and the shutter timing signal corresponding to the obtained luminance Is calculated from the shutter timing calculation LUT 46 and set.
[0059]
As a result, when the shooting scene is FIG. 4A, as in the first embodiment, images for two screens with different exposure amounts at 1/60 sec and 1/500 sec shown in FIG. Since a signal is obtained, an image with a wide dynamic range adapted to the photographic scene can be obtained by synthesizing the image signals for two screens obtained by the main photographing in the camera signal processing circuit 6 by a known method. .
[0060]
As described above, according to the present embodiment, in the shooting scene adaptive shooting mode, the shooting scene is pre-shot with the preset shutter timing signals ST1, ST2, and ST3 to acquire information on the dynamic range, and the combined information The tone conversion characteristics with noise and the like removed from the histogram, and the main shooting shutter timing signal is set based on the tone conversion characteristics, so that the main shooting is performed. It is possible to obtain a good image with a wide dynamic range adapted to the shooting scene without always driving the AE function. Further, since the gradation conversion characteristic calculated by the gradation conversion characteristic calculation circuit 44 is supplied to the camera signal processing circuit 6 and used for the conversion process of the image signal obtained by the main photographing, the image processing of the main photographing is performed. Therefore, it is not necessary to obtain tone conversion characteristics. Therefore, the image processing for the main photographing can be performed easily and quickly.
[0061]
It should be noted that the present invention is not limited to the above-described embodiment, and many variations or modifications can be made. For example, in the above-described embodiment, in the shooting scene adaptive shooting mode, the shooting scene is pre-shot with three different shutter timing signals to acquire information on the dynamic range of the shooting scene. The number of timing signals is not limited to three, and can be any number of two or more. In the above embodiment, the case of a shooting scene in which two shutter timing signals are set for actual shooting has been described as an example. However, depending on the shooting scene, one or more shutter timing signals for main shooting are used. In some cases, the camera signal processing circuit 6 does not synthesize the image, and in the case of two or more, the image is synthesized. Obtainable.
[0062]
In the above embodiment, the electronic shutter function of the CCD image pickup device 1 is controlled via the TG 24 by the shutter timing signal in the pre-shooting and the main shooting in the shooting scene adaptive shooting mode. Instead of the electronic shutter function, the aperture / shutter mechanism 3 is controlled, or both the electronic shutter function and the aperture / shutter mechanism 3 of the CCD image pickup device 1 are controlled to obtain an image signal of a desired exposure condition in the shooting scene. Can also be obtained.
[0063]
【Effect of the invention】
As described above, according to the present invention, prior to the main shooting, the shooting scene is pre-shot under different exposure conditions to acquire information about the dynamic range, and the main shooting is performed based on the acquired information about the dynamic range. Thus, an image with a wide dynamic range adapted to the shooting scene can be obtained without always driving the AE function even in a shooting scene having a large difference in brightness.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an overall schematic configuration of a digital still camera showing a first embodiment of the present invention.
FIG. 2 is a block diagram showing a configuration of an example of a shutter timing control circuit shown in FIG.
FIG. 3 is a flowchart showing an operation in a shooting scene adaptive shooting mode according to the first embodiment.
FIG. 4 is a diagram illustrating an example of a shooting scene and its brightness distribution.
FIG. 5 is a diagram for explaining a pre-photographing operation according to the first embodiment;
FIG. 6 is a diagram for explaining a peak value detection operation of a histogram for setting a shutter timing signal for actual photographing in the first embodiment.
FIG. 7 is also a diagram for explaining an operation for calculating a shutter timing signal from a peak value of a histogram.
FIG. 8 is a block diagram showing an overall schematic configuration of a digital still camera showing a second embodiment of the present invention.
9 is a block diagram showing a configuration of an example of a shutter timing control / tone calculation circuit shown in FIG. 8;
FIG. 10 is a diagram for explaining an operation of calculating gradation conversion characteristics according to the second embodiment.
FIG. 11 is also a diagram for explaining an operation of calculating a shutter timing signal from gradation conversion characteristics.
FIG. 12 is a diagram for explaining a wide dynamic range image acquisition method;
[Explanation of symbols]
1 CCD image sensor
2 Lens
3 Aperture / Shutter Mechanism
4 amplifiers
5 A / D converter
6 Camera signal processing circuit
7 AF, AE, AWB detection circuit
8 Shutter timing control circuit
9 CPU
10 Selection switch
11 Bus line
12 Memory controller
13 DRAM
14 Compression circuit (JPEG)
15 Memory card
16 Memory card I / F
17 Display circuit
18 Liquid crystal display (LCD)
19 PC
20 PCI / F
21 Strobe device
22 Input keys
23 Shutter timing ROM
24 Timing generator (TG)
31 switches
32 Signal synthesis circuit
33 Signal distribution calculation circuit
34 Signal distribution analysis circuit
35 Shutter timing calculation circuit
36 LUT for shutter timing calculation
38 Shutter timing control / tone calculation circuit
41 switch
42 Signal synthesis circuit
43 Signal distribution calculation circuit
44 Gradation conversion characteristic calculation circuit
45 Shutter timing calculation circuit
46 LUT for shutter timing calculation

Claims (7)

Information acquisition means for acquiring information related to the dynamic range of the shooting scene under a plurality of exposure conditions prior to the main shooting;
Information synthesizing means for synthesizing information on the dynamic range acquired by the information acquiring means;
Histogram calculating means for calculating a histogram of the combined information combined by the information combining means;
Gradation conversion characteristic calculation means for calculating gradation conversion characteristics based on information on the histogram calculated by the histogram calculation means;
Photographing means for performing actual photographing based on the gradation conversion characteristic calculated by the gradation conversion characteristic calculating means;
An imaging device comprising: The photographing means includes
The imaging apparatus according to claim 1 , further comprising shooting control information calculation means for calculating shooting control information for performing actual shooting based on the tone conversion characteristics calculated by the tone conversion characteristic calculation means. . The imaging apparatus according to claim 1, wherein the information regarding the dynamic range acquired by the information acquisition unit is luminance information regarding a shooting scene. The imaging apparatus according to claim 2 , wherein the imaging control information calculated by the imaging control information calculation unit is information for driving a shutter. The photographing means has a flash light emitting means for irradiating light to a photographing scene, and is configured to control the flash light emitting means based on the photographing control information calculated by the photographing control information calculating means. The imaging device according to claim 2 or 4 . 3. An information processing unit that performs multiple shootings based on the shooting control information by the shooting unit and combines image signals of a plurality of images obtained by the multiple shootings. , 4 or 5 . The gradation conversion characteristic calculation means, among the histogram calculated by said histogram calculating means, according to claim 1 or 2, characterized in that calculating a gradation conversion characteristic based on the histogram of the predetermined value or more frequencies Imaging device.

Images