JP3927825B2 - Exposure control method and apparatus, and imaging method and apparatus using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exposure control method and apparatus using a means or method for determining an appropriate exposure in an imaging apparatus, particularly a digital camera or the like.
[0002]
[Prior art]
As one means for determining the exposure of the digital camera, there is a feedback type exposure determining means. In order to always optimize the brightness of the liquid crystal screen of the digital camera, the exposure is corrected by always cycling, and the exposure at the time of photographing is determined using the data of the feedback type exposure determination means.
[0003]
Further, the scan type exposure determining means performs photometry a plurality of times with a plurality of predetermined exposure values in order to cope with a sudden change in brightness due to a scene change. Then, the optimum exposure is determined based on the photometric data.
[0004]
[Problems to be solved by the invention]
However, the feedback type exposure determining means has a certain time constant or correction value limit to prevent oscillation of the exposure value. For this reason, there is a problem that it is not possible to quickly respond to a change in brightness due to an abrupt scene change, and an accurate exposure cannot be obtained.
[0005]
Furthermore, when the optical viewfinder type digital camera without a liquid crystal screen, or when the liquid crystal screen display is turned off, the feedback method cannot be effectively used.
Further, since the scan type exposure determining means needs to perform exposure a plurality of times, there is a problem that a time lag of the shutter release occurs.
[0006]
The present invention has been made in view of such a situation, and an object thereof is to provide an exposure control method and apparatus capable of appropriate exposure control, and an imaging method and apparatus using these.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the present invention constantly monitors the brightness, and provides feedback type exposure determination means for keeping the brightness of an image to be taken appropriate, and the brightness of the image at a plurality of predetermined different exposures. A scan type exposure determining unit that determines an appropriate exposure and a final exposure for photographing from the exposure value determined by the feedback type exposure determining unit or the scan type exposure determining unit are determined using a signal obtained by photometric measurement. The exposure control apparatus has a photographing exposure determination means.
[0008]
Further, the present invention is an imaging apparatus including an imaging unit, an image processing unit that performs image processing on image data obtained by the imaging unit, and a data writing unit that records image processed image data. A data processing unit including the exposure control device, wherein the data processing unit is an imaging device that sends a control signal to the imaging unit via the imaging control unit based on image data obtained by the imaging unit. Is.
[0009]
The present invention also provides a feedback exposure determination process for constantly monitoring the brightness and maintaining the brightness of the image to be photographed properly, and a signal obtained by measuring the brightness of the image at a plurality of predetermined different exposures. , A scanning exposure determination step for determining an appropriate exposure, and a photographing exposure determination step for determining a final exposure for photographing from the exposure value determined by the feedback type exposure determination step or the scan type exposure determination step The exposure control method has the following.
[0010]
The present invention is also an imaging method in which image data obtained by imaging is subjected to image processing and image processed image data is written, and data processing is performed using any one of the above exposure control methods. The imaging method includes a data processing step and sends a control signal to the imaging unit via the imaging control unit based on the image data obtained by imaging in the data processing step.
[0011]
Further, the present invention provides a first imaging unit that captures a subject image, and determines an exposure value for photographing while performing exposure control so as to sequentially correspond to the brightness of the subject image repeatedly captured by the imaging unit. Exposure control in which exposure control is performed by selectively using an exposure control mode and a second exposure control mode in which exposure control is performed at a plurality of preset different exposure values to determine an exposure value for shooting. And an exposure control device having means.
[0012]
The present invention also includes a first exposure control mode that repeatedly captures a subject image and determines an exposure value for shooting while performing exposure control so as to sequentially correspond to the brightness of the subject image repeatedly captured. An exposure control method for performing exposure control during shooting by selectively using a second exposure control mode in which exposure control is performed at a plurality of preset different exposure values to determine an exposure value for shooting. is there.
[0013]
According to the present invention, when an abrupt scene change does not occur, the shutter time lag does not occur because shooting is performed based on the exposure value determined by the feedback type exposure determination means. In addition, when an abrupt scene change occurs, it is possible to obtain an accurate exposure value by performing shooting based on the exposure value determined by the scan type exposure determining means.
[0014]
Therefore, it is possible to accurately obtain the exposure at the time of a sudden scene change in the feedback type or scan type exposure determining means used conventionally, and to avoid problems such as the shutter release time lag.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
[0016]
FIG. 1 is a block diagram showing a schematic configuration of a digital camera of the present invention. First, an operation when the liquid crystal finder is ON before the shutter is pressed will be described.
[0017]
The imaging unit 101 includes a lens system, an aperture, a shutter, an electronic shutter, a CCD, an A / D converter, and the like, and an image projected on the CCD by the lens system is output as a digital signal. Computing from the digital signal obtained by the data processing unit 102 image capturing section 101, the average value Y, the diaphragm to equalize the brightness Y _ref as a target, the control signal values for controlling the electronic shutter speed To do.
[0018]
FIG. 2 is a more detailed block diagram of the data processing unit 102. In the figure, the digital signal obtained by the imaging unit 101 is sent to the feedback type exposure determination unit 201. Here, an average luminance value Y of the digital signal is obtained, and a control signal value B _vf sent to the imaging control unit 103 is obtained based on the average luminance value Y.
[0019]
The following expression is an expression for _obtaining a control signal value B _vf for controlling the average value Y and Y _ref of the digital signal. Here, _Av is an aperture control value, _Tv is an electronic shutter control value, _Sv is a CCD sensitivity control value, and _Bvf is a control signal value. The _{ΔB vf} (exposure correction value) and B _vf values obtained here are held until this value is next obtained.
[0020]
ΔB _vf = log ₂ (Y / Y _ref )
B _v = A _v + T _v −S _v
B _vf = B _v + ΔB _vf
Next, the imaging control unit 103 controls the aperture and the electronic shutter inside the imaging unit 101 based on the control signal value B _vf received from the data processing unit 102. By performing feedback control on this, the average value Y of the digital signal output from the imaging unit 101 is controlled to be always equal to Y _ref .
[0021]
Next, the movement during shutter release will be described.
[0022]
△ B _vf shutter is held in the feedback-type exposure determination unit 201 when the shutter _release, B _vf value is read. The absolute value (hereinafter referred to as “ABS (ΔB _vf )”) is obtained by the determination unit 202 and the _{ΔB vf} value read here is compared with a preset threshold value ΔB _v TH. .
[0023]
Even in this comparison, when ABS (ΔB _vf ) is smaller than ΔB _v TH, the control value B _vf is sent to the imaging control unit 103 as the imaging exposure value B _v to control the aperture and shutter. The main exposure shooting is performed. When ABS (ΔB _vf ) is larger than ΔB _v TH, information is sent to the scan type exposure determination unit 203, and scan type exposure control is performed.
[0024]
Here, the scan type exposure control will be described below.
[0025]
Photometry is performed using three control values B _v0 , B _v1 , and B _{v2 having} different exposure values determined in advance. If the average luminance value of the digital data obtained by each control value is Y ₀ , Y ₁ , Y ₂ , and the target luminance value is Y _ref , three control values _{ΔB v0} , _{ΔB v1} , ΔB _v2. Can be calculated by the following equation.
[0026]
_{ΔB v0} = log ₂ (Y ₀ / Y _ref )
ΔB _v1 = log ₂ (Y ₁ / Y _ref )
ΔB _v2 = log ₂ (Y ₂ / Y _ref )
Next, an exposure control value B _vS is obtained based on the smallest of ABS ( _{ΔB v0} ), ABS ( _{ΔB v1} ), and ABS ( _{ΔB v2} ). For example ABS (△ _B v0), when ABS (△ _B v1), among the _{ABS (△ B v2) ABS (} △ B v1) is smallest is _{B vS} is calculated by the following equation. A _v1 , T _v1 , and S _v1 are an aperture control value, an electronic shutter control value, and a CCD sensitivity control value at the exposure control value B _v1 .
[0027]
B _v1 = A _v1 + T _v1 −S _v1
B _vS = B _v1 + _{ΔB v1}
As a control value B _vS photographing exposure value B _v obtained here is sent to the imaging control unit 103, the diaphragm, and controls the shutter, the exposure shooting is performed. The digital signal obtained by the main exposure shooting in the imaging unit 101 is sent to the image processing unit 104, where image processing such as color processing and luminance processing, edge enhancement processing, gamma processing, and JPEG conversion processing is performed, and data writing is performed. The data is sent to the unit 105 and data is written to the recording medium.
[0028]
In the present embodiment, the method of performing photometry three times and obtaining the photographic exposure value in the case of performing the scan type exposure control has been described. However, the number of photometry is not limited to three times, but is reduced to two times or four. It may be increased to 5 times or 5 times.
[0029]
Next, a second embodiment of the present invention will be described below.
[0030]
FIG. 3 is a flowchart showing the operation in the present embodiment. In FIG. 3, in step S301, the feedback-type exposure determining means always monitors the image data to be captured, and feedback control is performed so that the average luminance of the image always becomes the target value. Further, the exposure control value is here determined for each feedback loop △ B _vf, B _vf is held until new data is obtained.
[0031]
Here, when the shutter is released, the absolute value ABS (ΔB _vf ) of the _{ΔB vf} value held in the feedback type exposure determining means at that time and the preset _{ΔB v} TH Comparison is performed (step S302). Even in this comparison, if ABS (ΔB _vf ) is smaller than ΔB _v TH, B _vf is sent as an exposure control value to the final exposure value determining means in step S304.
[0032]
If ABS (ΔB _vs ) is larger than ΔB _v TH, the exposure control value B _vs obtained by the scan type exposure determining means in step S303 is sent to the final exposure determining means (step S304).
[0033]
In the exposure determining means in step S304, the aperture value A _v , shutter speed value T _v , and CCD sensitivity value S _v used for shooting are determined from the received exposure control value (either B _vf f or B _vs ). Pre-exposure is performed with this setting. Based on the data obtained by this pre-exposure, the average luminance Y _{ave of the} image is calculated, and the brightness difference _{ΔB vl} from the target luminance is obtained.
[0034]
However, ( _{DELTA) Bvl} is _{calculated |} required by the following formula _| equation.
[0035]
_{ΔB vl} = log ₂ (Y _ave / Y _ref )
In order to correct this _{ΔB vl} to zero, ΔA _v and ΔT _v are obtained. Here obtained △ _{A v,} △ _{T v is,} A _v, T _v, is sent to the imaging control unit with _{S v} (step S305).
[0036]
Here, each functional block and processing procedure shown in the various embodiments described above may be configured by hardware, or configured by a microcomputer system including a CPU or MPU, ROM, RAM, and the like, and the operation thereof is performed by ROM. Alternatively, it may be realized according to a work program stored in the RAM. In addition, what is implemented by supplying a software program for realizing the function to the RAM so as to realize the function of the function block and operating the function block according to the program is also included in the scope of the present invention. include.
[0037]
In this case, the software program itself realizes the functions of the above-described embodiments, and the program itself and means for supplying the program to a computer, for example, a recording medium storing such a program are included in the present invention. Configure. As a storage medium for storing such a program, for example, a floppy disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-I, a CD-R, a CD-RW, a DVD, a zip, a magnetic, in addition to the ROM and the RAM. A tape or a non-volatile memory card can be used.
[0038]
Further, by executing the program supplied by the computer, not only the functions of the above-described embodiments are realized, but also the OS (operating system) or other application software in which the program is running on the computer. Needless to say, such a program is included in the embodiment of the present invention even when the functions of the above-described embodiment are realized.
[0039]
Furthermore, after the supplied program is stored in the memory provided in the function expansion board of the computer or the function expansion unit connected to the computer, the CPU or the like provided in the function expansion board or function expansion unit based on the instructions of the program Needless to say, the present invention includes the case where the functions of the above-described embodiment are realized by performing part or all of the actual processing.
[0040]
【The invention's effect】
As described above, according to the present invention, the exposure is appropriately controlled by the feedback type exposure determining unit and the scan type exposure determining unit in response to the occurrence of a sudden scene change, so that an accurate exposure value can always be obtained. Is possible.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration example of a digital camera according to an embodiment of the present invention.
FIG. 2 is a block diagram illustrating a configuration example of a data processing unit according to the embodiment of the present invention.
FIG. 3 is a flowchart showing a flow of processing in the second embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 101 Imaging part 102 Data processing part 103 Imaging control part 104 Image processing part 105 Data writing part 201 Feedback type exposure determination part 202 Determination part 203 Scan type exposure determination part

Claims (22)

Use feedback type exposure determination means to monitor the brightness at all times and maintain the brightness of the image to be captured properly, and use a signal obtained by metering the brightness of the image at a plurality of predetermined different exposures. Scanning exposure determining means for determining exposure, and photographing exposure determining means for determining final exposure for photographing from the exposure value determined by the feedback type exposure determining means or the scan type exposure determining means Exposure control device. When the absolute value of the exposure correction value obtained by the feedback type exposure determination unit at the time of shutter release is smaller than a predetermined threshold value, the exposure value obtained by the feedback type exposure determination unit is used to 2. The exposure control apparatus according to claim 1, wherein a final exposure for photographing is determined by the photographing exposure determining means. When the absolute value of the exposure correction value obtained by the feedback type exposure determining unit at the time of shutter release is larger than the threshold value, the photographing exposure determining unit based on the exposure value obtained by the scan type exposure determining unit. 3. The exposure control apparatus according to claim 1, wherein a final exposure for photographing is determined. The photographing exposure determining means performs pre-exposure based on one of the exposure value determined by the feedback-type exposure determining means and the exposure value determined by the scan-type exposure determining means. The exposure control apparatus according to claim 1, wherein a deviation from an appropriate exposure is obtained and a final exposure for photographing is determined. Using a feedback type exposure determination process to monitor the brightness at all times and maintain the brightness of the image to be captured properly, and using a signal obtained by metering the brightness of the image at a plurality of predetermined different exposures, A scan-type exposure determination step for determining exposure, and a photographing exposure determination step for determining a final exposure for photographing from the exposure value determined by the feedback-type exposure determination step or the scan-type exposure determination step. Exposure control method. When the absolute value of the exposure correction value obtained by the feedback type exposure determination process at the time of shutter release is smaller than a predetermined threshold value, the exposure value obtained in the feedback type exposure determination process is used based on the exposure value obtained by the feedback type exposure determination process. 6. The exposure control method according to claim 5, wherein the final exposure for photographing is determined by the photographing exposure determining step. When the absolute value of the exposure correction value obtained by the feedback type exposure determination process at the time of shutter release is larger than the threshold, the photographing exposure determination process is performed based on the exposure value obtained by the scan type exposure determination process. The exposure control method according to claim 5, wherein a final exposure for photographing is determined. In the photographing exposure determination step, pre-exposure is performed using either one of the exposure value determined in the feedback-type exposure determination step and the exposure value determined in the scan-type exposure determination step, and the pre-exposure is performed. The exposure control method according to claim 5, wherein a deviation from an appropriate exposure is obtained and a final exposure for photographing is determined. An imaging apparatus comprising: an imaging unit; an image processing unit that performs image processing on image data obtained by the imaging unit; and a data writing unit that records image data that has undergone image processing. A data processing unit including the exposure control device according to claim 1, wherein the data processing unit sends a control signal to the imaging unit via the imaging control unit based on image data obtained by the imaging unit. An imaging apparatus characterized by being sent out. An image pickup method in which image data obtained by image pickup is subjected to image processing and image processed image data is written, using the exposure control method according to any one of claims 5 to 8. An imaging device comprising a data processing step for data processing, wherein a control signal is sent to the imaging unit via the imaging control unit based on the image data obtained by imaging in the data processing step Method. The computer-readable storage medium which stored the program for functioning a computer as each means of any one of Claims 1-4. A computer-readable storage medium storing a program for executing the processing procedure of the method according to claim 5. An imaging unit that captures a subject image; a first exposure control mode that determines an exposure value for shooting while performing exposure control so as to sequentially correspond to the brightness of the subject image repeatedly captured by the imaging unit; Exposure control means for performing exposure control at the time of shooting by selectively using a second exposure control mode for performing exposure control at a plurality of different set exposure values and determining an exposure value for shooting. A featured exposure control device. Whether the exposure control means performs exposure control during shooting using the exposure value for shooting determined in the first exposure control mode based on the exposure correction value obtained in the first exposure control mode. The exposure control apparatus according to claim 13, wherein whether to perform exposure control at the time of shooting is selected by using an exposure value for shooting determined by the second exposure control mode. The exposure control means uses an exposure value for photographing determined in the first exposure control mode based on whether or not an exposure correction value obtained in the first exposure control mode is smaller than a predetermined value. 14. The method according to claim 13, further comprising: selecting whether to perform exposure control at the time of shooting or to perform exposure control at the time of shooting using an exposure value for shooting determined by the second exposure control mode. Exposure control device. When the exposure correction value obtained in the first exposure control mode is smaller than the predetermined value, the exposure control unit performs shooting using the exposure value for shooting determined in the first exposure control mode. If the exposure correction value obtained by the first exposure control mode is greater than the predetermined value, the exposure value for shooting determined by the second exposure control mode is used. The exposure control apparatus according to claim 13, wherein exposure control at the time of photographing is performed. The exposure control means is an exposure for photographing determined in the first exposure control mode based on whether or not an absolute value of an exposure correction value obtained in the first exposure control mode is smaller than a predetermined value. 14. The method of selecting whether to perform exposure control at the time of shooting using a value or to perform exposure control at the time of shooting using an exposure value for shooting determined by the second exposure control mode. An exposure control device according to claim 1. When the absolute value of the exposure correction value obtained in the first exposure control mode is smaller than the predetermined value, the exposure control device sets the exposure value for photographing determined in the first exposure control mode. Is used to perform exposure control at the time of shooting, and when the absolute value of the exposure correction value obtained by the first exposure control mode is larger than the predetermined value, it is determined by the second exposure control mode. The exposure control apparatus according to claim 13, wherein exposure control at the time of photographing is performed using the exposure value of the above. In response to the operation of the shutter release operation member, the exposure control means performs exposure control at the time of shooting using the exposure value for shooting determined by the first exposure control mode or the second exposure control. The exposure control apparatus according to any one of claims 13 to 18, wherein whether to perform exposure control at the time of shooting is selected using an exposure value for shooting determined by a mode. Different from the first exposure control mode in which a subject image is repeatedly picked up and exposure value for photographing is determined while performing exposure control corresponding to the brightness of the subject image that is repeatedly picked up a plurality of times. An exposure control method characterized in that exposure control at the time of shooting is performed by selectively using a second exposure control mode in which exposure control is performed with an exposure value to determine an exposure value for shooting. A first exposure control mode for repeatedly capturing a subject image and determining an exposure value for shooting while performing exposure control so as to sequentially correspond to the brightness of the repeatedly captured subject image; and a plurality of preset times An exposure control program for performing exposure control at the time of shooting by selectively using a second exposure control mode for performing exposure control with different exposure values and determining an exposure value for shooting. The computer-readable storage medium according to claim 21, wherein the exposure control program is stored.

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