JPH11331688A - Digital camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To widen the width of exposure correction without adding a photometric element by setting a proper exposure value against an image pickup element based on image data which is obtained by picking-up the image without adding exposure correction. SOLUTION: In a digital camera 100, images are repeatedly picked-up before executing main photographing and an exposure value is continually updated so as to follow the lightness of a subject based on the image obtained by picking-up the image. When a photographer indicates exposure correction, image picking-up based on the exposure value without correction is executed by a fixed frequency while image picking-up is executed based on the exposure value with correction added (image data fetching) during repeatedly picking-up images. Then, a proper correction value is calculated based on image data which is obtained by image picking-up by the exposure value without correction and the exposure value after correction is obtained by adding an indicated quantity of exposure correction to the calculated proper exposure value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital camera capable of performing exposure correction for an appropriate exposure value.

[0002]

2. Description of the Related Art In a digital camera, a degree of exposure, that is, an exposure value is determined by a shutter speed (hereinafter referred to as "SS").
), Gain, and (in models with variable aperture, further aperture). And
An exposure value such that the brightness of an image obtained by imaging is a predetermined optimum (optimum value or optimum range),
That is, these variables are usually automatically set so as to achieve an appropriate exposure value. Such an operation mode is called an auto mode.

In a digital camera in which an auto mode is prepared, the photographer can make a manual operation (instruction from outside) to correct a proper exposure value which is automatically set. What was done is known. FIG. 8 is a flowchart showing a procedure of an operation of a conventional digital camera configured to be able to perform the exposure correction to set an exposure value before actual photographing. This operation is realized by a microcomputer provided in the camera controlling each component similarly provided in the camera.

When the processing for setting the exposure is started, first, the microcomputer drives an image pickup device such as a CCD provided in a camera (step ST61). As a result, image data of the subject obtained by the image sensor is
It is taken into the microcomputer (step ST6)
2). Subsequently, based on the image data, a degree of exposure that achieves a preset optimal (ie, optimal value or optimal range) image brightness, that is,
An appropriate exposure value is calculated. At the same time, the gain and the SS corresponding to the appropriate exposure value, that is, the appropriate gain and the appropriate SS are calculated (step ST63).

Next, it is detected whether or not a switch operation for instructing exposure correction has been performed (step ST6).
4). If exposure correction has been instructed, the already calculated proper exposure value is corrected (corrected) by the instructed correction amount (step ST65). At this time, the gain and SS corresponding to the corrected exposure value are also calculated at the same time. If the exposure correction has not been instructed, this process (step ST65) is skipped.

Next, it is determined whether or not the gain should be reset, that is, whether or not the calculated gain is different from the currently set gain (step ST6).
6). If it is determined that the gain should be reset, the gain is reset (step ST67). Next, it is determined whether or not to reset the SS, that is, whether or not the calculated SS is different from the currently set SS (step ST68). If it is determined that the SS should be reset, the SS is reset (step ST69).

[0007] Thereafter, the exposure setting process ends. In a conventional digital camera capable of exposure correction, the exposure value (including gain and SS) is set in the above procedure. Thereby, it is possible to perform imaging and recording at an exposure value shifted from an appropriate exposure value based on an instruction of a photographer.

[0008] The above operation will be described more specifically according to the photographer's viewpoint as follows. For example,
It is assumed that a photographer performs photographing by adding an exposure correction of two-step overexposure as a correction amount. At this time, prior to the actual photographing, first, a proper exposure value is obtained, and further, a proper SS and a proper gain are obtained from image data obtained by imaging with the image sensor. For example, by delaying the SS by two stages with respect to the determined appropriate SS, 2
It is possible to take a picture with overexposure.

In the case of photographing with a camera, the scene to be photographed usually changes from moment to moment.
In other words, the brightness of the subject generally changes constantly. Accordingly, the proper exposure value also changes constantly.
Therefore, before the actual photographing, the imaging is repeatedly performed, whereby the proper exposure value is repeatedly updated.

That is, the exposure setting process shown in FIG. 8 is repeatedly executed until the actual photographing is performed, whereby the change in the light amount of the subject and the correction amount due to the change by the photographer during the period are performed. The exposure value after correction, and the gain and SS for realizing it, are constantly updated in accordance with the change in. In other words, feedback control of the exposure value is performed based on image data obtained by repeatedly performing image capturing (image capture). As a result, based on the appropriate exposure value that follows the change in the brightness of the subject, it is possible to perform the main shooting with the corrected exposure value to which the photographer has added the desired amount of exposure correction.

[0011]

Incidentally, as described above, the proper exposure value is obtained based on image data obtained by imaging with an image sensor. For example, if exposure correction is performed over two steps, an appropriate exposure value (for a different scene) for the next image capture is calculated based on image data obtained by capturing images over two steps.

That is, an image is taken with a gain and SS corresponding to the corrected exposure value, and an appropriate exposure value is calculated based on the image data obtained thereby, and further correction is performed. As described above, the image data that is the basis for determining the exposure value is the image data obtained by imaging based on the corrected exposure value.

However, the image data thus obtained may not correctly reflect the brightness of the scene. This is because the scene may be too bright and the value of the image data may be saturated. In this case, the brightness of the scene is estimated to be lower (darker) than the reality. For example, the appropriate SS which is originally 1/250 is 1/125
Will be determined. Therefore, when exposure correction is performed over two steps, the SS after correction is originally 1/60.
Where it should be, it is determined to be 1/30. In other words, although the photographer desires two-step-over, it is actually set to three-step-over.

[0014] Then, the image data obtained by the next imaging is further deeply saturated. As a result, a vicious cycle is repeated, and an appropriate exposure value cannot be obtained. Naturally, an exposure value obtained by adding a two-step over correction to the appropriate exposure value cannot be obtained. That is, the photographer cannot perform the actual photographing with the desired exposure value.

In the case where an image is always taken at an appropriate exposure value, the obtained image data falls within a range that does not saturate unless an image is taken in a very bright scene. In the case where a slightly bright scene is imaged, the above-described problem occurs. The same applies when the number of exposure correction steps is large, such as +4 steps or +5 steps.

Further, when photographing is performed with exposure correction of two-step underexposure, the value of image data may converge on a darker side for the same reason. Again, in this case,
An appropriate exposure value cannot be obtained, and an exposure value obtained by adding a two-step under correction to the appropriate exposure value cannot be obtained. In particular, such a situation occurs when a slightly dark scene is photographed by adding exposure compensation on the minus side.

FIG. 9 is an explanatory diagram schematically showing the problems described above. In FIG. 9, a curve C0 exemplifies a brightness distribution of an image obtained when a subject is imaged with an appropriate exposure value. That is, in the curve C0, for example,
The average value over the entire width of the screen corresponds to the preset optimal brightness. If the photographer does not instruct exposure correction, an image whose brightness distribution is indicated by the curve C0 is obtained.

On the other hand, when the photographer gives an instruction to add one step of exposure correction to the plus side (for example, to double the exposure value), the brightness distribution of an image obtained by imaging becomes As shown by the curve C1, the image is shifted one step (for example, to twice the brightness) toward the bright side. Conversely, when an instruction to add one step of the exposure correction to the minus side (for example, to reduce the exposure value by 倍) is issued, the brightness distribution of the image obtained by imaging is represented by a curve C2. Thus, the image is shifted to the dark side by one step (for example, to 明 る times the brightness).

In the exposure setting process shown in FIG.
Based on the image data corresponding to C1 and C2 (steps ST61 and ST62), a calculation is executed to calculate an appropriate exposure value (step ST63). The appropriate exposure value is calculated, for example, such that the average value of the brightness expressed by the image data over the entire screen or a partial area is a value within a predetermined optimum range. If the average value is half the value in the optimum range, the current exposure value is doubled to determine the appropriate exposure value. Then, the designated one-step exposure correction is performed, so that the exposure value for the next imaging is set (steps ST65 to ST6).
9).

Therefore, if exposure correction is instructed and the image obtained by imaging correctly reflects the brightness distribution as represented by the curves C1 and C2, the setting is made next. The exposure value is obtained as a correct value. However, when the photographer gives an instruction to increase the exposure correction to the positive (plus) side (for example, to increase the exposure value by four times), the brightness distribution of the image obtained by the imaging is represented by a curve C3. As shown, there is a shift to a brighter side (eg, four times brighter).

At this time, in the image corresponding to the curve C3,
Part of it becomes white. That is, if the exposure correction is excessively applied to the positive side, part or all of the image is saturated to the bright side. Similarly, if the exposure compensation is excessively applied to the negative side,
Some or all of the image converges on the dark side. Curve C
When an appropriate exposure value is calculated based on at least partially saturated image data as shown in FIG. 3, for example, the curve C3
Is calculated, and if the calculation is performed based on this average value, the calculation result includes an error. That is, in the next imaging, imaging based on the correct exposure value is not performed.

As a result, the width of the exposure correction has to be limited to a narrow range. In an example of a popular digital camera in which image data obtained by an image sensor and input to a microcomputer is 8-bit data, a correction amount of about ± 1.5 EV is a limit. In order to eliminate this limitation and enable exposure correction of, for example, ± 4 EV, it was necessary to separately provide a photometric element for calculating an appropriate exposure value.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in the prior art, and has as its object to provide a digital camera capable of expanding the range of exposure correction without adding a photometric element. And

[0024]

An apparatus according to a first aspect of the present invention sets a proper exposure value at which the brightness of an image is set in advance to be optimal based on image data obtained by imaging with an image sensor. In a digital camera including a proper exposure value setting means and an exposure correction means for performing exposure correction on the proper exposure value, the proper exposure value setting means performs the exposure correction on the image sensor. The proper exposure value is set based on image data obtained by imaging without adding.

According to a second aspect of the present invention, in the digital camera according to the first aspect, a display means for displaying image data obtained by repeatedly imaging with the image pickup device; A display for displaying, on the display unit, image data obtained by applying the exposure correction to the image sensor without displaying the image data obtained by imaging without applying the correction on the display unit; And control means.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS <A. Configuration> FIG. 1 is a block diagram showing a configuration of a digital camera according to an embodiment. The digital camera 100 includes a main microcomputer (hereinafter abbreviated as “main microcomputer”) 1. The main microcomputer 1 internally includes a CPU and a memory in which a program that defines the operation of the CPU is stored. Thereby, the main microcomputer 1
It functions as a control unit that controls the operation of each component of the digital camera 100 described below. The main microcomputer 1 that operates based on the program
Instead of hardware with no program,
It is also possible to configure a control unit.

The components controlled by the main microcomputer 1 include a distance measuring module 2 for receiving reflected light from a subject and outputting distance information of the subject.
A switch group 3 including a power switch for manually operating (ie, instructing from outside) 00, an electrically rewritable EEPROM, and inspection values at the time of shipment from a factory regarding a model difference for each digital camera 100; ROM 4 for recording various set values immediately before power-off, display member 5 composed of a liquid crystal display (LCD) or the like for displaying a subject image and set values for photographing, and transmitting image data to a personal computer or an external monitor. An external interface 6 for input / output, a detachable recording medium 7 for recording image data obtained by shooting,
RAM 8 for performing arithmetic processing on image data obtained by photographing, a solid-state imaging device 9 configured to capture a subject image via a lens, a timing generator (TG), and the like for driving the solid-state imaging device 9 Image sensor driver 10 for generating a pulse for causing the image to be generated, analog amplifier 11 for amplifying image data as an analog signal output from solid-state image sensor 9, analog amplifier 11
The A / D converter 12 that converts the analog signal amplified by the digital signal into a digital signal and outputs the digital signal to the main microcomputer 1 and the focus lens group 14 are driven in the optical axis direction, and the position of the focus lens group 14 is detected. A focus driver / position detection sensor 13 and the like are provided.

The focus lens group 14 forms a part of an image pickup lens group which is an image pickup optical system. The image pickup lens group has a fixed lens group 141 fixed in addition to the focus lens group 14. . The solid-state imaging device 9 composed of a CCD converts an image of the formed object into an electric signal in an analog format, and converts the converted image signal into analog analog 1
Output to 1. Further, the image sensor driver 10 drives the solid-state image sensor 9 so as to realize a predetermined exposure time based on the control of the main microcomputer 1. This exposure time corresponds to the shutter speed (SS).

Since the image data output from the solid-state imaging device 9 is a weak analog signal, it is amplified by the analog amplifier 11 and then input to the A / D converter 12 as described above. The gain described above corresponds to the gain of the analog amplifier 11. The SS defined by the solid-state imaging device 9 and the analog amplifier 11
The degree of exposure (exposure value) is determined by the two variables of the gain defined by.

<B. Overall Flow of Operation> The overall flow of the operation of the digital camera 100 realized by the control of the main microcomputer 1 is represented by a flowchart in FIG.
As shown in FIG. 2, when the photographer turns on the power by turning on the power switch, first, an initial setting process is performed (step ST1). That is, the microcomputer is reset and other predetermined initialization processing is performed. Next, monitoring of a switch operation performed by the photographer is performed (step ST2), and standby for the next switch operation is performed.

Thereafter, an exposure start switch (hereinafter referred to as a "release switch") is half-pressed (hereinafter referred to as "S").
1 operation) is detected. If the S1 operation has not been performed, the S1 off process is performed (step ST4). Conversely, if the S1 operation has been performed, the S1 on process is performed (step ST4).
5). When these processes are completed, the process proceeds to step ST
Return to 2.

The initial setting process (step ST1) corresponds to the process shown in FIG.
It is executed according to the flow of That is, when the power switch provided in the switch group 3 is pushed by the photographer to turn on the power, first,
The main microcomputer 1 is reset (step ST1).
1). Since each port of the main microcomputer 1 is set to a default state by the reset, the initial setting of the main microcomputer 1 such as setting a port to be used is subsequently performed (step ST12).

Thereafter, the inspection values at the time of shipment from the factory regarding the model differences and various setting values immediately before the last power-off, for example, the type of the flash mode or the type of the image compression mode, are read out from the ROM 4, and according to the set values. Is set (step ST13). Next, the presence / absence and type of the recording medium 7 and the recordable capacity based on the type are confirmed (step ST14).
While the position of the focus lens group 14 is monitored by the position detection sensor 13, the focus lens group 14
It is moved to the initial position set in OM4 (step ST15).

Subsequently, the display member 5 is activated (step ST16). As a result, various setting values and information such as the recordable capacity of the recording medium and the like are displayed on the display member 5. At this stage, the solid-state imaging device 9 has not been operated yet, and the image of the subject is not displayed on the display member 5.

Next, the main microcomputer 1 sends, for example, S to the image pickup device driver (TG) 10 as a spare for the image pickup operation.
S (in other words, the exposure time) is set to the initial SS (for example, 1
/ 30 seconds) (step ST17). The initialization of the image sensor driver 10 is completed, and the operation of the image sensor driver 10 starts output of image data from the solid-state image sensor 9, and the captured image is displayed on the display member 5.

At this time, the gain of the analog amplifier 11 is also set to a predetermined initial value, for example, 1 (step ST).
18). Thereafter, the solid-state imaging device 9 continuously outputs image data. As a result, the image of the subject is displayed on the display member 5 as a moving image. Thus, the initial setting process (step ST1) is completed, and the process proceeds to step ST1.
2 (FIG. 2), and monitoring of the switch operation is performed.

Returning to FIG. 2, during the period in which the S1 operation is not performed, as described above, the main microcomputer 1 repeats the loop of steps ST2, ST3, and ST4 to perform the next camera operation. stand by. At this time, if the photographer does not operate the camera with the switch group 3 for a certain period of time, the power is turned off by the timer function prepared in the main microcomputer 1. As a result, power consumption can be reduced. Usually, this fixed time is set to about several minutes.

<C. S1 off processing and S1 on processing>
FIG. 4 is a flowchart showing an internal flow of the S1 off process (step ST4). When the S1 off process is started, an exposure setting process for setting an exposure value is performed (step ST20). Details of the procedure will be described later. Thereafter, the S1 off process ends, and the process proceeds to step S
Return to T2 (FIG. 2).

FIG. 5 shows the S1 ON process (step ST5).
6 is a flowchart showing an internal flow of the first embodiment. When the S1 ON process (step ST5) is started, the main microcomputer 1 drives the distance measuring module 2. Thereby, data (distance data) corresponding to the distance from the camera to the subject is obtained (step ST21). S1
If the subject is captured by an optical finder not illustrated in FIG. 1 while the operation is continued, the distance measuring module 2 receives the reflected light from the subject and thereby obtains distance data.

The distance measuring module 2 is configured as, for example, a conventionally known external light passive module. Data relating to the correspondence between the distance data obtained by the distance measuring module 2 and the distance from the camera to the subject is stored in the ROM 4 as adjustment values. The ROM 4 further stores data (focal length data) relating to the focal length of the imaging lens group including the focus lens group 14 and the fixed lens group 141. The main microcomputer 1 calculates the extension amount of the focus lens group 14 for focusing on the subject based on the distance data obtained by the distance measuring module 2 and the data stored in the ROM 4 (step ST22).

Next, the main microcomputer 1 drives the focus driver / position detection sensor 13 based on the calculated feeding amount. Thereby, the extension amount of the focus lens group 14 is set to the calculated value.
As a result, focusing is achieved (step ST23).

Next, an exposure setting process for setting an exposure value is executed (step ST20). The procedure of the exposure setting process executed here is the S1 off process (step S
This is the same as the procedure of the exposure setting process executed in T4). Thereafter, it is detected whether or not the S1 operation has been released (step ST24).

If it has been released, the process of step ST5 ends, and the process returns to step ST2 (FIG. 2). If not released, it is detected whether or not the photographer has performed a full-press operation of the release switch (hereinafter, referred to as “S2 operation”) (step ST25). If the S2 operation has not been performed, the process returns to step S20.
That is, while the S1 operation is continued, the microcomputer waits while repeating the exposure setting process until the S2 operation is performed.

When the S2 operation is performed, the process shifts to the image capturing and recording process (step ST26), and the exposure for the main photographing is started based on the exposure value already set. That is,
The main shooting of the subject is performed in synchronization with the S2 operation corresponding to the shutter pressing, and the image obtained thereby is recorded. The details of this imaging and recording process will be described later.

Thereafter, the microcomputer waits until both the S1 operation and the S2 operation are released (step ST27), and when those operations are released, the processing of step ST5 ends, and the processing proceeds to step ST2. Return to (FIG. 2).

<D. Flow of Exposure Setting Process> FIG.
6 is a flowchart showing an internal flow of an exposure setting process (step ST20) included in the flow of FIG.
When the exposure setting process is started, first, the main microcomputer 1
Sends the control signal to the image sensor driver 10 to drive the solid-state image sensor 9 with the SS already set (step ST31).

As a result, the solid-state imaging device 9 converts the image of the subject formed thereon into an electric signal and outputs the electric signal to the analog amplifier 11. The analog amplifier 11 amplifies the input electric signal with a set gain.
The amplified signal is converted into a digital signal by the A / D converter 12, and then input to the main microcomputer 1 as image data (step ST3).
2).

Next, it is detected whether or not a switch operation for instructing exposure correction has been performed (step ST3).
3). At this stage, for example, at this stage, the main microcomputer 1 executes step ST from the power-on to the present.
The number of times of image pickup (image capture) performed in 31 is counted. The number of times of imaging is determined when exposure compensation is instructed.
It may be the number of times of imaging performed in step ST31.

If the exposure correction is instructed, the number of times of imaging N
Is divided by 10 to determine the remainder f (N) (step ST
34). If the remainder f (N) is the value “1”, the process proceeds to step S
The process shifts to T35, and if the value is "0", the process proceeds to step ST43.
The process proceeds to step ST44 if it is any other value.
Move to.

That is, only when the number of times of imaging N is 1, 11, 21,..., The process of calculating an appropriate exposure value (step ST35), and on the basis of the calculated appropriate exposure value. Processing for calculating exposure value after correction (step ST3)
7) is executed. In step ST35, based on the image data obtained in this imaging (step ST32), the degree of exposure that realizes the preset optimal (ie, optimal value or optimal range) image brightness, that is, , An appropriate exposure value is calculated.

The imaging in step ST32 is performed without exposure correction when N = 1. Also, as described later, when N = 11,21,...
Imaging is performed without exposure correction. Therefore, the calculation of the appropriate exposure value is always performed based on the image data obtained by imaging (step ST32) without performing exposure correction.

At this time, at the same time, the gain and SS corresponding to the proper exposure value, that is, the proper gain and the proper SS
Is calculated. The main microcomputer 1 performs the calculation by using the RAM 8 as a calculation memory also when calculating these appropriate values. The procedure of this calculation itself is well known in the art, and a detailed description thereof will be omitted. The calculated proper exposure value (including the proper gain and the proper SS) is stored in the memory (step ST36). Even if the memory for storing the appropriate exposure value is the RAM 8, a memory (not shown) provided inside the main microcomputer 1.
It may be.

Thereafter, the currently calculated proper exposure value is corrected (corrected) by the specified correction amount (step ST37). At this time, S for realizing the corrected exposure value
S and gain are calculated at the same time. Then, the exposure value after correction (including SS and gain) is adopted as the exposure value to be set (including SS and gain) (step ST38).

Next, it is determined whether or not the gain should be reset, that is, whether or not the adopted gain is different from the currently set gain (step ST39). If it is determined that the gain should be reset, the gain of the analog amplifier 11 is reset (step ST40).

Subsequently, it is determined whether or not the SS should be reset, that is, whether or not the adopted SS is different from the currently set SS (step ST41). If it is determined that the setting should be reset, the SS is reset for the image sensor driver 10 (step ST42). That is, as SS and gain for the next imaging,
A value to which exposure correction has been applied based on the appropriate exposure value is set. Thereafter, the process of step ST20 ends.

The next imaging (step ST32), that is, the imaging corresponding to the number of imagings N = 2, 12, 22,... (F (N) = 2), is performed at the set exposure value after correction. It is done based on. Then, neither the calculation of the appropriate exposure value (step ST335) nor the calculation of the corrected exposure value (step ST37) is performed according to the determination in step S34. Therefore, through the processing of steps ST39 to ST42, the number of times of imaging N =
The value set when 1, 11, 21,... (F (N) = 1) is maintained as it is.

At the same time, in step ST44, the image displayed on the display member 5 is updated to the image obtained by the current imaging. Therefore, the display member 5 includes
The latest image captured based on the corrected exposure value is displayed. The main microcomputer 1 creates display image data for displaying an image on the display member 5 by performing image processing on digital image data obtained by imaging. At this time, the main microcomputer 1 performs the operation by using the RAM 8 as a memory for the operation. The display image data is image data converted into a format that is optimal for displaying on the display member 5. Thereby, an image can be displayed on the display member 5.

The number of times N = 3-9, 13-19, 23-29,... (F (N) =
The imaging corresponding to 3 to 9) and the processing subsequent to the imaging are performed in the same manner as the number of imagings N = 2, 12, 22,... (F (N) = 2). Therefore, the number of times of imaging N = 2-10, 12-20, 22-30,... (F (N) = 2 to 9,
The imaging (step ST32) corresponding to (0) is performed after the correction set based on the image data obtained by the imaging of N = 1, 11, 21,... (F (N) = 1). Is performed based on the exposure value. Further, every time an image is taken, the image displayed on the display member 5 is updated (step ST44). Therefore, the display member 5 displays the latest image captured based on the corrected exposure value.

In particular, the number of times of imaging N = 10, 20, 30,... (F (N) =
After the imaging of 0) is performed, the appropriate correction value calculated last time, that is, the number of imagings N = 1, 11, 21,... (F (N) = 1)
The appropriate correction value calculated based on the image data obtained by the image pickup is read out from the memory (step ST4).
3). Then, in the subsequent processing of steps ST39 to ST42, the next imaging, that is, the number of imagings N = 11, 21, 31,... (F (N) =
The SS and the gain for the imaging in 1) are set.

As a result, the number of times of imaging N = 11, 21, 31,... (F
The imaging of (N) = 1) is also executed based on the exposure value to which no exposure correction is applied, similarly to the imaging of the imaging number N = 1. Of these, only the imaging with the imaging frequency N = 1 is performed in step ST.
.. Are performed based on the exposure value as the initial value set in step 1, and the subsequent number of times of imaging N = 11, 21, 31,... Is performed based on the appropriate exposure value set last time. .

When the determination in step ST33 does not apply, that is, when the photographer has not instructed the exposure correction, the appropriate exposure value is calculated in the same procedure as in step ST35, and the appropriate gain and appropriate SS corresponding thereto are calculated. Is performed (step ST45). Then, an appropriate exposure value that has not been corrected is adopted as the exposure value to be set (step ST46).

At this time, the image displayed on the display member 5 is updated to an image based on the latest image data (step ST44). That is, when there is no instruction for exposure correction, the displayed image is updated each time a new image is obtained by imaging. Thereafter, in order to realize a proper gain and a proper SS, steps ST39 to ST39 are executed.
Through 42, the gain or / and SS are reset.

As described above, in the digital camera 100, the image pickup is repeatedly performed before starting the main image pickup, and the exposure value follows the brightness of the subject based on the image obtained by the image pickup. Constantly updated. And
When the photographer instructs the exposure correction, in the repetitive imaging, the imaging based on the corrected exposure value (capture of image data) is mixed, and at a fixed frequency, without correction. Imaging is performed based on the exposure value.

Then, the appropriate correction value is calculated based on image data obtained by imaging with the exposure value without correction, and the corrected exposure value is specified with respect to the calculated appropriate exposure value. It is obtained by adding an amount of exposure correction. Further, the next imaging without exposure correction is performed based on the appropriate exposure value calculated last time.

As a result, the proper exposure value is correctly calculated even when the subject becomes brighter or darker when the photographer instructs the exposure correction. That is, the appropriate exposure value is correctly calculated without being affected by the magnitude of the exposure correction. Therefore, the restriction on the width of the exposure correction is relaxed, and the width of the exposure correction can be expanded. Moreover, there is no need to additionally provide a photometric element.

When the photographer instructs the exposure correction, the image displayed on the display member 5 is updated only with the image data obtained by capturing the image with the corrected exposure value, and the exposure correction is not performed. Is not updated by the image data picked up by. For this reason, the photographer can perform the actual photographing while checking the image obtained by the desired exposure correction through the display member 5 in real time.

Note that the proper exposure value is updated only once every ten imagings. However, since the imaging cycle is about 30 times / second, the proper exposure value is about 1 /. It will be updated every 3 seconds. Since the change in the brightness of the subject is slow enough to take a sufficiently long time as compared with 1/30 seconds, which is the imaging cycle, about 1/3
Even if the proper exposure value is updated every second, there is no practical problem.

In the above description, an example is shown in which an appropriate exposure value is calculated once every 10 shots. However, generally, an appropriate exposure value is calculated once every M (M ≧ 2) shots. You may comprise so that an exposure value may be calculated. At this time, the operation of the device is the same as the operation described above, except that “10” is replaced with “M”.

<E. Imaging Recording Process> FIG. 7 is a flowchart showing an internal flow of the imaging recording process (step ST26) included in the flow of FIG. At the start of the image capturing and recording process, first, the exposure for the main image capturing is started. That is, the main microcomputer 1 sends the control signal to the image sensor driver 10 to drive the solid-state image sensor 9 with the already set SS (step ST5).
1).

The analog amplifier 11 amplifies the image data of the main photographing obtained by the solid-state imaging device 9 with a gain that has been set. The amplified image data is converted to a digital format by the A / D converter 12, and then input to the main microcomputer 1 (step ST52).

The main microcomputer 1 uses the RAM 8 as an arithmetic memory to perform image processing on the input digital photographing image data (step ST53). Through this image processing, the display member 5
Then, display image data for displaying an image and recording image data for recording on the recording medium 7 are generated.
The recording image data is image data that has been subjected to compression processing so that image data having a large data size can be efficiently recorded on the recording medium 7 having a limited memory size. As a compression processing method, for example, the JPEG method is adopted.

The display image data obtained through the image processing is displayed on the display member 5. That is, since the image obtained by the main shooting is displayed on the display member 5, the photographer can visually confirm the image obtained by the main shooting (after-view). At the same time, the image data for recording is recorded on the recording medium 7 (step ST).
54).

The recording image data may be transferred not only to the recording medium 7 but also to an external personal computer or the like via the external interface 6. Further, it is also possible to externally control the digital camera 100 by externally inputting a control signal to the main microcomputer 1 through the external interface 6. For example, instead of the manual operation of the switch group 3, an instruction signal can be input from the outside.

As the external interface 6, for example, a terminal for a serial cable such as RS-422C used for a personal computer, an NTSC output terminal for enabling connection to a television receiver, or a printer for enabling connection to a printer Output terminals are prepared.

When the process of step ST54 is completed, the imaging and recording process (step ST26) ends, and the process proceeds to step ST27 (FIG. 5). Note that, when the imaging (acquisition of an image) of the main imaging performed through steps ST51 and ST52 is imaging corresponding to the remainder f (N) = 1, the exposure setting process (step ST20)
The exposure value (SS and gain) adopted in the immediately preceding imaging in (i.e., imaging with the remainder f (N) = 0) is set as it is. Therefore, in the actual photographing when the exposure correction is instructed, the image pickup is always performed with the corrected exposure value to which the exposure correction has been applied, regardless of the value of the number N of times of image pickup.

The main microcomputer 1 can be equivalently expressed as a control unit having various processing means. The functions described in the above-described flowcharts are performed by these processing units.

For example, in step ST35 in FIG.
The processing of ST36, ST43, ST45, ST46 and the like is performed by a proper exposure value setting means for setting a proper exposure value. Further, the processing such as steps ST37 and ST38 is performed by exposure correction means for performing exposure correction. Further, the process of step ST44 is performed by the display control means for controlling the display of the image data on the display member 5.

<F. Modification 1> In the above description, the time at which the digital camera 100 performs imaging (acquisition of image data) without exposure correction is determined based on the number of times of imaging. However, in general, the present invention is not limited to such a form. For example, on the basis of time, a form in which imaging without exposure correction is performed at regular intervals, or
When the brightness of the entire scene (subject) suddenly changes, it is also possible to implement a mode in which imaging without exposure correction is performed. In general, the object of the present invention is achieved if the imaging performed without the exposure correction is inserted into the repetitive imaging performed with the exposure correction performed prior to the main photographing.

<G. Modification 2> In the above description, an example in which the variable defining the exposure value is only two variables of SS and gain has been described. However, the digital camera 100 can include an aperture member so that the aperture can be changed. At this time, the exposure value is SS, gain, and
It is specified by three variables of aperture.

At this time, in the initial setting process (step ST1) of FIG. 3, along with steps ST17 and ST18,
The initial setting of the aperture may be additionally performed. In the exposure setting process (step ST20) of FIG. 6, in addition to the processes of steps ST39 to ST42 for setting the gain and the SS, the process of setting the aperture similarly to them
It may be performed additionally. In the simplest case, a mode in which the exposure value is defined only by the SS or only by the gain can be similarly implemented.

[0081]

According to the first aspect of the present invention, the proper exposure value is
The setting is made based on image data obtained by imaging with an exposure value without correction. Therefore, if the subject becomes brighter while the photographer instructs exposure compensation,
Alternatively, even when the image becomes dark, the proper exposure value is correctly calculated. That is, the appropriate exposure value is correctly calculated without being affected by the magnitude of the exposure correction. This alleviates the restriction on the width of the exposure correction, so that the width of the exposure correction can be increased without additionally providing a photometric element.

In the device according to the second aspect of the invention, the display means displays only image data obtained by capturing an image with the corrected exposure value. For this reason, the photographer can perform photographing while checking the image obtained by the desired exposure correction through the display member in real time.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a digital camera according to an embodiment.

FIG. 2 is an overall flowchart of the operation of the digital camera according to the embodiment.

FIG. 3 is an internal flowchart of an initial setting process of FIG. 2;

FIG. 4 is an internal flowchart of the S1 off process of FIG. 2;

FIG. 5 is an internal flowchart of the S1 on process of FIG. 2;

FIG. 6 is an internal flowchart of an exposure setting process of FIGS. 4 and 5;

FIG. 7 is an internal flowchart of the image capturing and recording process of FIG. 5;

FIG. 8 is a flowchart of an exposure setting process according to the related art.

FIG. 9 is an explanatory diagram showing a problem of the related art.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04N 5/92 H04N 5/92 H

Claims (2)

[Claims] 1. An appropriate exposure value setting means for setting an appropriate optimal exposure value for setting an optimal brightness of an image based on image data obtained by imaging with an imaging device; On the other hand, in a digital camera including: an exposure correction unit that performs exposure correction, the appropriate exposure value setting unit performs, on the image sensor, image data obtained by performing imaging without performing the exposure correction. A digital camera, wherein the proper exposure value is set based on the setting. 2. A display means for displaying image data obtained by iteratively imaging with the image sensor, and displaying image data obtained by imaging without applying the exposure correction to the image sensor. 2. A display control means for displaying image data obtained by adding the exposure correction to the image pickup device and taking an image without displaying the image on a display means, and displaying the image data on the display means.
A digital camera according to claim 1.