JP2004140640A - Digital camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a digital camera capable of fast photographing while suppressing the generation of smears. <P>SOLUTION: When a shutter release button 44 is fully pressed, a CPU 26 enters a photographing operation. If a high-luminance component which possibly induces a smear is present in a subject field, the CPU 26 controls the exposure period of an image sensor 12 with a mechanical shutter 16. When the high-luminance subject is not present in the subject field, the CPU 26 controls the exposure period by an electronic shutter function of the image sensor 12. Further, a saturation decision circuit 42 decides whether the high-luminance component is present in the subject field. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a digital camera, and more particularly to, for example, a CCD (Charge Coupled Device) image sensor, an electronic shutter for controlling a charge accumulation period of the image sensor, and opening and closing an incident optical path from a field to a light receiving surface of the image sensor. The present invention relates to a digital camera having a mechanical shutter.
[0002]
[Prior art]
An example of this type of conventional digital camera is disclosed in Patent Document 1. According to this conventional technique, the exposure period is controlled by the electronic shutter at the time of high-speed shooting with flash emission. That is, the mechanical shutter, which is inferior to the electronic shutter in terms of high-speed operation, does not operate during the exposure period, so that the strobe light is not blocked by the light shielding member (blade member) of the mechanical shutter, and there is no so-called exposure unevenness. Good flash emission photography can be realized. On the other hand, at the time of shooting without strobe light emission without strobe light emission, the exposure period is controlled by the mechanical shutter. Therefore, even if a high-luminance object such as the sun exists in the object scene, it is possible to suppress the occurrence of smear due to incident light from the object.
[0003]
[Patent Document 1]
JP-A-11-212136
[0004]
[Problems to be solved by the invention]
However, in the above-described conventional technology, even when the exposure period is not required to be controlled by the mechanical shutter, in other words, even when there is no high-luminance component that induces smear in the object field, the strobe non-flash photographing is performed. Sometimes the exposure period is controlled by a mechanical shutter. That is, since the length of the exposure period is limited by the performance of the mechanical shutter, there is a problem in that high-speed shooting as with an electronic shutter cannot be realized.
[0005]
Therefore, a main object of the present invention is to provide a digital camera capable of realizing high-speed shooting while suppressing generation of smear.
[0006]
It is another object of the present invention to provide a digital camera capable of performing photographing according to a high-speed photographing condition under the condition.
[0007]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided a digital camera including an electronic shutter for controlling a charge accumulation period of an image sensor and a mechanical shutter for opening and closing an incident optical path from a field to a light receiving surface of the image sensor. A digital camera, further comprising an activation unit that activates only the electronic shutter among the shutter and the mechanical shutter, wherein the predetermined condition includes a luminance condition that a luminance component exceeding a threshold exists in the object scene. is there.
[0008]
According to a second aspect of the present invention, an activation command arbitrarily given in a digital camera having an electronic shutter for controlling a charge accumulation period of an image sensor and a mechanical shutter for opening and closing an incident optical path from a field to a light receiving surface of the image sensor. The digital camera further includes a receiving unit that receives the activation command, and an activation unit that activates only the electronic shutter among the electronic shutter and the mechanical shutter when the activation command is received.
[0009]
[Action]
In the first aspect, when the luminance condition that a luminance component exceeding the threshold exists in the object scene is not satisfied, only the electronic shutter of the electronic shutter and the mechanical shutter is activated by the activation unit. Therefore, in this case, the exposure period is controlled by the electronic shutter. On the other hand, when the luminance condition is satisfied, that is, when there is a luminance component exceeding the threshold value in the object scene, the exposure period can be controlled by the mechanical shutter by activating the mechanical shutter.
[0010]
In one embodiment of the present invention, detecting means for detecting the luminance of each of a plurality of small areas formed in the object scene, comparing means for comparing the luminance of each of the small areas detected by the detecting means with a threshold value, and comparing Determining means for determining whether a luminance condition is satisfied based on a comparison result by the means;
[0011]
Note that the predetermined condition may further include an exposure condition that the optimum exposure period is equal to or longer than the minimum value of the exposure period that can be controlled by the mechanical shutter. In this case, the mechanical shutter is not activated when the exposure condition is not satisfied even when the luminance condition is satisfied, that is, when the optimal exposure period is a short period that cannot be handled by the mechanical shutter.
[0012]
Then, the image sensor may read out electric charges in a sequential scanning format. Further, a CCD type image sensor can be used as such an image sensor.
[0013]
In the second invention, when the receiving unit receives the activation command, only the electronic shutter of the electronic shutter and the mechanical shutter is activated by the activation unit. That is, only the electronic shutter can be forcibly activated by a manual operation. In this case, the exposure period is controlled by the electronic shutter.
[0014]
【The invention's effect】
According to the first aspect, when there is no luminance component exceeding the threshold in the object scene, the exposure period is controlled by the electronic shutter, so that high-speed photographing that cannot be performed by the mechanical shutter can be realized. On the other hand, when there is a luminance component exceeding the threshold in the object scene, the exposure period can be controlled by the mechanical shutter, so that the occurrence of smear due to the existence of the luminance component can be suppressed. That is, high-speed shooting can be realized while suppressing the occurrence of smear.
[0015]
According to the second aspect, only the electronic shutter can be forcibly activated by a manual operation. Therefore, under conditions in which high-speed imaging that cannot be handled by a mechanical shutter is required, imaging that always meets the request is performed. It can be performed.
[0016]
The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.
[0017]
【Example】
Referring to FIG. 1, a digital camera 10 of this embodiment has an interline transfer type CCD image sensor (hereinafter simply referred to as an image sensor) 12. Between the light receiving surface 12a of the image sensor 12 and the focus lens 14, a mechanical shutter (shielding member) 16 and an aperture mechanism 18 are provided. Of these, the mechanical shutter 16 opens and closes in response to a shutter control signal supplied from a shutter driver 20, and one of the aperture mechanisms 18 responds to an aperture control signal supplied from an aperture driver 22, that is, its aperture diameter, Change the F value.
[0018]
When a shooting mode for shooting a subject is selected by operating the mode key 24, the CPU 26 instructs the shutter driver 20 to open. The shutter driver 20 supplies a shutter control signal corresponding to this command to the mechanical shutter 16. The mechanical shutter 16 opens in accordance with the shutter control signal, whereby an optical image of the subject enters the light receiving surface 12a of the image sensor 12. The CPU 26 also instructs the aperture driver 22 to set the F value so that the F value becomes a default value (for example, about F4 to F6). The aperture driver 22 supplies an aperture control signal corresponding to this command to the aperture mechanism 18, whereby the F value is set to a default value.
[0019]
Further, in response to the selection of the photographing mode, the CPU 26 instructs a TG (Timing Generator) 28 to repeat the pre-exposure and the thinning-out reading. The TG 28 supplies a timing signal corresponding to the command to the image sensor 12, and the image sensor 12 exposes the optical image of the subject according to the supplied timing signal, and removes a part of the electric charge accumulated by the exposure. Output in the next one frame period. That is, when the photographing mode is initially selected, a low-resolution raw image signal is output from the image sensor 12 every frame period.
[0020]
The raw image signal of each frame output from the image sensor 12 is input to a CDS (Correlated Double Sampling) / AGC (Automatic Gain Control) circuit 30, where it is subjected to a correlated double sampling process and a gain adjustment process. , A / D conversion circuit 32. The A / D conversion circuit 32 converts the input raw image signal into raw image data which is a digital signal, and inputs the converted raw image data to the signal processing circuit 34.
[0021]
The signal processing circuit 34 performs a series of processes such as color separation, white balance adjustment, gamma correction, and YUV conversion on the input raw image data, and inputs the YUV data generated by these processes to the video encoder 36. The video encoder 36 converts the input YUV data into an NTSC composite image signal, and inputs the converted composite image signal to the liquid crystal monitor 38. As a result, a real-time moving image of the subject, a so-called through image, is displayed on the screen of the liquid crystal monitor 38.
[0022]
Further, the Y data among the YUV data generated by the signal processing circuit 34 is input to an AE (Automatic Exposure) / AF (Autofocus) evaluation circuit 40. The AE / AF evaluation circuit 40 calculates a luminance evaluation value Ey representing the degree of luminance of the subject image and a focus evaluation value Ef representing the degree of focusing of the focus lens 14 on the subject based on the input Y data. .
[0023]
More specifically, the AE / AF evaluation circuit 40 divides the scene (screen) into 256 blocks 50, 50,... Having 16 rows and 16 columns as shown in FIG. Then, in each block 50, a luminance evaluation value Ey of each block 50 is calculated by integrating the Y data of each pixel constituting the block 50, and a predetermined block (for example, an The focus evaluation value Ef is calculated by integrating the high-frequency components of the Y data in several blocks (50, 50,... Located at the center of the field).
[0024]
The signal processing circuit 34 also inputs the same Y data that is input to the AE / AF evaluation circuit 40 to the saturation determination circuit 42. Based on the input Y data, the saturation discriminating circuit 42 determines whether or not there is a high-luminance component in the object scene enough to saturate the screen, in other words, a high-luminance component that induces smear. Is determined.
[0025]
Specifically, as shown in FIG. 3, the saturation discriminating circuit 42 makes the object field (screen) finer than the above-described blocks 50, 50,..., For example, several pixels to several tens of pixels (horizontal m pixels × vertical). (n pixels; m = 1 to 10, n = 1 to 10). Then, in each small block 60, the Y data of each pixel is integrated, and the integrated value Iy is compared with a predetermined threshold value α. Here, when there is at least one small block 60 whose integral value Iy exceeds the threshold value α, the saturation determination circuit 42 determines that a high luminance component exists in the object scene, and outputs a determination result H of “1”. I do. On the other hand, when the integrated value Iy is equal to or smaller than the threshold value α in all the small blocks 60, 60,..., The saturation determination circuit 42 determines that no high-luminance component exists in the object scene, and the determination result is “0”. H is output. This determination result H is input to the CPU 26. The threshold value α is set, for example, to a value of 95% to 99% of the maximum value Iymax (α = 0.95 Iymax to 0.99 Iymax) of the maximum value Iymax of the integral value Iy.
[0026]
When the shutter button 44 is half-pressed, the CPU 26 takes in the luminance evaluation value Ey and the focus evaluation value Ef from the AE / AF evaluation circuit 40. Then, the optimum exposure period Ts and the optimum aperture value As are calculated based on the taken luminance evaluation value Ey, and the calculated optimum exposure period Ts is set to TG28. The aperture driver 22 is controlled so that the aperture value becomes As. The CPU 26 also controls the focus driver 46 so that the focus evaluation value Ef increases, and sets the focus lens 14 to a focus position.
[0027]
Further, in response to the half-press of the shutter button 44, the CPU 26 stores the determination result H input from the saturation determination circuit 42 in a register H built therein. The determination result H stored in the register H is determined until the shutter button 44 is released from the half-pressed state, that is, the shutter button 44 is fully pressed or the shutter button 44 is turned off (the operator's finger releases the shutter button 44). Until the button 44 is released), it is updated every frame period.
[0028]
Then, when the shutter button 44 is fully pressed, the CPU 26 starts a shooting operation. That is, the CPU 26 determines whether or not the above-described optimal exposure period Ts is equal to or less than a minimum value Tp (for example, Tp = 1/1000 [s]) of the exposure period that can be handled by the mechanical shutter 16, that is, the mechanical shutter 16 It is determined whether the shutter speed according to the exposure period Ts can be handled. The CPU 26 also checks whether the value stored in the register H is “0” or “1”, that is, whether or not a high luminance component exists in the object scene.
[0029]
Here, if the shutter speed according to the optimal exposure period Ts is a speed that cannot be handled by the mechanical shutter 16 or if there is no high-luminance component in the object scene, the CPU 26 sends one frame to the TG 28. Of the main exposure and reading of all pixels. The TG 28 supplies a timing signal corresponding to a command from the CPU 26 to the image sensor 12. As a result, all the electric charges existing in the image sensor 12 at that time, more specifically, electric charges accumulated in a photosensitive portion (photodiode) (not shown) of the image sensor 12 and remaining in a vertical transfer portion and a horizontal transfer portion (not shown). The accumulated charge is once discarded. Then, after this disposal, the main exposure is started, whereby electric charges are accumulated in the photosensitive portion of the image sensor 12. Then, when the optimum exposure period Ts has elapsed since the start of the main exposure, all the electric charges accumulated in the photosensitive section are simultaneously transferred to the vertical transfer section. That is, the exposure period is controlled by the electronic shutter function of the image sensor 12. The charge transferred to the vertical transfer unit is sequentially transferred to the horizontal transfer unit for one horizontal line, and the charge transferred to the horizontal transfer unit is sequentially read for one pixel. As a result, a high-resolution raw image signal for one frame is output from the image sensor 12 in a sequential scanning format.
[0030]
The high-resolution raw image signal output from the image sensor 12 is input to the A / D conversion circuit 32 via the CDS / AGC circuit 30, where it is converted into high-resolution raw image data. Then, the converted raw image data is input to the signal processing circuit 34, where the raw image data is converted into YUV data by performing the above-described series of processing. The signal processing circuit 34 is provided with a compression command from the CPU 26, and in response to the compression command, performs a compression process according to the JPEG (Joint Photographic Expert Group) method on the YUV data. Further, the signal processing circuit 34 is also provided with a recording command from the CPU 26, and the signal processing circuit 34 records the compressed JPEG compressed image file on the memory card 48 in response to the recording command.
[0031]
On the other hand, if the shutter speed according to the optimal exposure period Ts is a speed that can be handled by the mechanical shutter 16 and a high-luminance component exists in the object scene, the CPU 26 sends the TG 28 one-frame In addition to the exposure and all-pixel readout instructions, a vertical transfer section clear instruction described later is given. The TG 28 supplies a timing signal corresponding to a command from the CPU 26 to the image sensor 12. As a result, all the electric charges existing in the image sensor 12 at that time are once discarded, and thereafter, the main exposure is started, and the electric charges are accumulated in the photosensitive portion of the image sensor 12. Then, when the optimum exposure period Ts has elapsed since the start of the main exposure, the CPU 26 controls the shutter driver 20 to close the mechanical shutter 16. This completes the main exposure. That is, the exposure period is controlled by the mechanical shutter 16.
[0032]
At the timing immediately after the mechanical shutter 16 is closed, the vertical transfer unit of the image sensor 12 is cleared according to a timing signal based on the above-described vertical transfer unit clear command. Specifically, the electric charge existing in the vertical transfer unit is transferred to the horizontal transfer unit, and is finally discarded. After the vertical transfer section of the image sensor 12 is cleared in this way, all the electric charges accumulated in the photosensitive section are simultaneously transferred to the vertical transfer section. The charges transferred to the vertical transfer unit are sequentially read out via the horizontal transfer unit. As a result, a high-resolution raw image signal for one frame is output from the image sensor 12 in a sequential scanning format.
[0033]
Thereafter, the same processing as described above is performed, and a JPEG compressed image file based on the high-resolution raw image signal is finally recorded on the memory card 48. After recording the JPEG compressed image file, the CPU 26 controls the shutter driver 20 to open the mechanical shutter 16. Then, the processing for displaying the through image described above is performed again.
[0034]
In order to realize such a series of photographing operations, the CPU 26 executes the processes shown in the flowcharts of FIGS. 4 and 5 according to the control program stored in the program memory 26a.
[0035]
Referring to FIG. 4, when shutter button 44 is half-pressed, CPU 26 waits for input of vertical synchronization signal Vsync in step S1. Then, when the vertical synchronization signal Vsync is input, the luminance evaluation value Ey is obtained from the AE / AF evaluation circuit 40 in step S3. Further, after calculating the optimum exposure period Ts based on the luminance evaluation value Ey in step S5, the optimum exposure period Ts is set to TG28 in step S7.
[0036]
After setting the optimal exposure period Ts, the CPU 26 compares the optimal exposure period Ts with the minimum value Tp of the exposure period that can be handled by the mechanical shutter 16 in step S9. Here, when the optimal exposure period Ts is equal to or longer than the minimum value Tp (Ts ≧ Tp), that is, when the shutter speed according to the optimal exposure period Ts is a speed that can be handled by the mechanical shutter 16, the process proceeds to step S11. Then, in this step S11, "1" is set to the flag G prepared in advance.
[0037]
On the other hand, when the optimal exposure period Ts falls below the minimum value Tp (Ts <Tp), that is, when the shutter speed according to the optimal exposure period Ts is a speed that cannot be handled by the mechanical shutter 16, the CPU 26 proceeds from step S9 to step S13. Proceed to. Then, in this step S13, "0" is set to the flag G described above. The flag G is an index indicating whether or not the shutter speed according to the optimal exposure period Ts is a speed that can be handled by the mechanical shutter 16. When the flag G is “1”, it indicates that the shutter can be handled by the mechanical shutter 16. “0” indicates that the mechanical shutter 16 cannot be used.
[0038]
After setting the flag G in step S11 or S13, the CPU 26 proceeds to step S15, and calculates the optimal aperture value As based on the luminance evaluation value Ey acquired in step S3 described above. Then, in step S17, after controlling the aperture driver 22 so that the F-number set by the aperture mechanism 14 becomes the optimal aperture value As, the process proceeds to step S19.
[0039]
In step S19, the CPU 26 performs focus adjustment based on a known contrast detection method. Specifically, the focus evaluation value Ef is obtained from the AE / AF evaluation circuit 40, and the focus driver 46 is controlled so that the obtained focus evaluation value Ef becomes large. Then, in step S21, it is determined whether or not the focus adjustment has been completed, that is, whether or not the focus lens 14 has been set to the in-focus position.
[0040]
Here, if it is determined that the focus adjustment has not been completed, the CPU 26 proceeds to step S23, and determines whether or not the shutter button 44 has been turned off. Then, when it is determined that the shutter button 44 has been turned off, a series of processes shown in this flowchart is ended. That is, if the shutter button 44 is turned off before the end of the focus adjustment, shooting is not performed. On the other hand, if the shutter button 36 has not been turned off, the process returns from step S23 to step S19.
[0041]
When determining that the focus adjustment has been completed in step S21, the CPU 26 proceeds to step S25. Then, after storing the determination result H input from the saturation determination circuit 42 in the register H in step S25, it is determined in step S27 whether the shutter button 44 has been turned off again. Here, when the shutter button 44 is turned off, a series of processes shown in this flowchart is ended. On the other hand, if the shutter button 44 has not been turned off, the process proceeds to step S29, and it is determined whether or not the shutter button 44 has been fully pressed. Steps S25 and S27 are repeated until the shutter button 44 is fully pressed, and when the shutter button 36 is fully pressed, the process proceeds from step S29 to step S31 in FIG.
[0042]
In step S31, the CPU 26 determines whether or not “1” is set in the flag G described above. If "1" is set in the flag G, the process proceeds to step S33, and it is determined whether "1" is stored in the register H.
[0043]
If "1" is stored in the register H in step S33, that is, the shutter speed according to the currently set optimum exposure period Ts is a speed that can be handled by the mechanical shutter 16, and a high luminance component is included in the object field. If exists, the CPU 26 proceeds to step S35. Then, after instructing the TG 28 to perform the main exposure for one frame and reading out all the pixels in this step S35, the TG 28 is given the above-described vertical transfer section clear instruction in step S37.
[0044]
As a result, all the electric charges present in the image sensor 12 at that time are once discarded, and thereafter, the main exposure is started. Then, the CPU 26 determines whether or not the optimum exposure period Ts has elapsed since the main exposure was started in step S39. Here, if it is determined that the optimal exposure period Ts has elapsed, the process proceeds to step S41, in which the shutter driver 20 is controlled to close the mechanical shutter 16. That is, the exposure period is controlled by the mechanical shutter 26. Immediately after the mechanical shutter 16 is closed, the vertical transfer section of the image sensor 12 is cleared at the timing based on the above-described vertical transfer section clear command. Then, after clearing the vertical transfer unit, all charges accumulated in the photosensitive unit of the image sensor 12 during the exposure period are simultaneously transferred to the vertical transfer unit. The charges transferred to the vertical transfer unit are sequentially read out via the horizontal transfer unit as described above. As a result, a high-resolution raw image signal for one frame is output from the image sensor 12 in a sequential scanning format.
[0045]
After the processing in step S41, the CPU 26 gives a compression command and a recording command to the signal processing circuit 34 in step S43. As a result, compression processing is performed by the signal processing circuit 34, and the JPEG compressed image file generated by this compression processing is recorded on the memory card 48.
[0046]
On the other hand, if “1” is not set to the flag G in step S31 (“0” is set), that is, the shutter speed according to the currently set optimal exposure period Ts depends on the mechanical shutter 16. If the speed is not possible, the CPU 26 proceeds to step S45. If “1” is not stored in the register H in step S33 (“0” is stored), that is, if there is no high-luminance component in the object scene, the process proceeds to step S45.
[0047]
In step S45, the CPU 26 instructs the TG 28 to perform main exposure for one frame and read all pixels. Thus, after all the electric charges present in the image sensor 12 at that time are once discarded, the main exposure is started. Then, in step S47, the CPU 16 determines whether or not the optimum exposure period Ts has elapsed since the start of the main exposure. When determining that the optimum exposure period Ts has elapsed, the CPU 16 proceeds to step S43. In this case, the electric charges accumulated in the photosensitive section of the image sensor 12 by the main exposure are simultaneously transferred to the vertical transfer section when the optimum exposure period Ts has elapsed as described above. That is, the exposure period is controlled by the electronic shutter. Then, the charges transferred to the vertical transfer unit are sequentially read out via the horizontal transfer unit, whereby a high-resolution raw image signal for one frame is output from the image sensor 12 in a sequential scanning format.
[0048]
After the process in step S43, the CPU 26 determines in step S49 whether the mechanical shutter 16 is in the closed state. Here, when the mechanical shutter 26 is in the closed state, the process proceeds to step S51, the shutter driver 20 is controlled to open the mechanical shutter 16, and a series of processes shown in this flowchart is ended. On the other hand, when the mechanical shutter 26 is not in the closed state, the step S51 is skipped, and the series of processing ends.
[0049]
As can be understood from the above description, according to the digital camera 10 of this embodiment, when a high luminance component exists in the object scene, the exposure period is limited by the mechanical shutter 16. Therefore, generation of smear due to the presence of the high luminance component can be suppressed. On the other hand, when there is no high luminance component in the object scene, in other words, when the possibility of occurrence of smear is low, since the exposure period is controlled by the electronic shutter, the mechanical shutter 16 cannot handle it. High-speed shooting can be realized. That is, high-speed shooting can be realized while suppressing the occurrence of smear. This is particularly effective when performing continuous shooting.
[0050]
If the shutter speed according to the optimal exposure period Ts is a speed that cannot be handled by the mechanical shutter 16, the exposure period is unconditionally controlled by the electronic shutter. Therefore, photographing under the condition according to the optimal exposure period Ts is guaranteed.
[0051]
In this embodiment, the image sensor 12 employs a so-called progressive scanning method of reading out electric charges in a progressive scanning manner, but may employ an interlaced scanning method. However, the present invention is particularly effective in a digital camera employing a progressive scanning image sensor. That is, some digital cameras that employ a progressive scanning image sensor do not have a mechanical shutter, and the exposure period is controlled only by the electronic shutter. In a digital camera whose exposure period is controlled only by such an electronic shutter, high-speed shooting is possible, but the occurrence of smear cannot be suppressed. Therefore, if the present invention is applied to such a digital camera, the advantage that high-speed shooting is possible is maintained, and the occurrence of smear is suppressed, so that the present invention is extremely effective.
[0052]
Further, in the classification of the charge transfer system, the image sensor 12 of the interline transfer system is used, but another system such as a frame transfer system or a frame interline transfer system may be used. Furthermore, in the classification of the element structure, the CCD type image sensor 12 is used, but the present invention is not limited to this, and another type such as a CID (Charge Injection Device) type may be used.
[0053]
Then, whether or not a high luminance component exists is determined for the entire object scene. However, the determination may be performed for a partial area of the object scene. For example, as indicated by a symbol X in FIG. 4, it may be determined whether or not a high luminance component exists in a central portion of the object field. Further, the value of the threshold value α serving as a reference for determination is not limited to the value described in this embodiment.
[0054]
Furthermore, the shape of the small block 60 may be square or rectangular, or may be other shapes. The size of the small block 60, that is, the values of m and n are not limited to the values described in this embodiment.
[0055]
Further, the same processing as that of the saturation determination circuit 42 may be executed by the CPU 26. In other words, the saturation determination circuit 42 may not be provided, and it may be determined by the processing of the CPU 26 whether or not a high luminance component exists in the object scene.
[0056]
Further, regardless of whether the determination result H by the saturation determination circuit 42 is “1” or “0”, that is, regardless of whether a high luminance component exists in the object scene, the mode key 24 The exposure period may be forcibly controlled by the electronic shutter by a manual operation by the user. In this way, under conditions that require high-speed shooting that cannot be handled by the mechanical shutter 16, shooting can always be performed according to the request.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a schematic configuration of an embodiment of the present invention.
FIG. 2 is an illustrative view for explaining processing contents of an AE / AF evaluation circuit in FIG. 1;
FIG. 3 is an illustrative view for explaining a processing content of a saturation determination circuit in FIG. 1;
FIG. 4 is a flowchart showing an operation of a CPU in the embodiment of FIG. 1;
FIG. 5 is a flowchart following FIG. 4;
[Explanation of symbols]
10. Digital camera
12 ... Image sensor
16 ... Mechanical shutter
26 ... CPU
42 ... Saturation determination circuit

Claims (6)

An electronic shutter that controls a charge accumulation period of an image sensor, and a digital camera that includes a mechanical shutter that opens and closes an incident optical path from a field to a light receiving surface of the image sensor.
An activation unit that activates only the electronic shutter among the electronic shutter and the mechanical shutter when a predetermined condition is not satisfied;
The digital camera according to claim 1, wherein the predetermined condition includes a luminance condition that a luminance component exceeding a threshold value exists in the object scene. Detecting means for detecting the luminance of each of a plurality of small areas formed in the object scene,
Comparing means for comparing the brightness of each of the small areas detected by the detecting means with the threshold value, and determining means for determining whether or not the brightness condition is satisfied based on a comparison result by the comparing means. The digital camera according to claim 1. The digital camera according to claim 1, wherein the predetermined condition further includes an exposure condition that an optimum exposure period is equal to or longer than a minimum value of an exposure period that can be controlled by the mechanical shutter. 4. The digital camera according to claim 1, wherein said image sensor reads charges in a sequential scanning format. 5. The digital camera according to claim 1, wherein said image sensor is a CCD type image sensor. An electronic shutter that controls a charge accumulation period of an image sensor, and a digital camera that includes a mechanical shutter that opens and closes an incident optical path from a field to a light receiving surface of the image sensor.
A digital camera, further comprising: accepting means for accepting an arbitrarily given enabling command; and enabling means for enabling only the electronic shutter among the electronic shutter and the mechanical shutter when the enabling command is received.

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