JP6883855B2 - Imaging device and control method of imaging device - Google Patents

Description

The present invention relates to an image pickup apparatus that performs pre-emission prior to the present emission and a control method for the image pickup apparatus.

Conventionally, in a digital still camera equipped with an electronic flash, it is widely practiced to obtain an appropriate exposure in the main light emission by performing pre-light emission prior to the main light emission at the time of shooting.

For example, there is known a method in which the inside of an imaging screen is divided into a plurality of regions, pre-emission metering is performed in each region, and the emission control of the main emission is performed from the result. Such a method is particularly effective because it can determine the state of the entire screen and perform appropriate light emission control.

Situations that require appropriate light emission control include, for example, the presence or absence of depth between the main subject and the background. Since an appropriate amount of reflected light can be obtained from the entire imaging screen when there is no depth, it is easier to obtain an appropriate exposure when the entire imaging screen is used as the photometric area, while when there is depth, the photometry is performed only from the main subject. It is easier to obtain proper exposure. That is, it is necessary to appropriately determine whether to use only the main subject as the light measurement area or the entire imaging screen including the background as the light measurement area according to the depth of the main subject and the background.

Patent Document 1 is mentioned as a technique for performing control according to a situation by measuring pre-emission in this way. In Patent Document 1, the degree of variation in the difference in luminance information between when the pre-flash is emitted and when it is not emitted is obtained. When the degree of variation is small, the entire imaging screen is used as the calculation area, and when the degree of variation is large, the imaging screen is displayed. An invention is disclosed in which the photometric calculation area of the present emission calculation is changed depending on the degree of variation so that a part of the calculation area is used.

Japanese Unexamined Patent Publication No. 2005-121834

However, the invention described in Patent Document 1 has the following problems.

First, there is a problem that it becomes difficult to determine the presence or absence of depth when the difference information can hardly be acquired. For example, when shooting in an environment with strong constant light such as outdoors in fine weather, the amount of pre-emission is relatively small with respect to the amount of constant light, and almost no reflection can be obtained. Therefore, the depth of the main subject and the background could not be discriminated, and proper exposure could not be obtained.

In addition, there is a problem that the brightness of the entire imaging screen cannot be determined only by the difference information. In the invention described in Patent Document 1, the depth between the main subject and the background can be determined by acquiring the difference information, but the brightness of the entire imaging screen is not evaluated. For example, consider a case where the background and the main subject are not separated and there is a large difference in brightness between the background and the main subject. In this case, since the variation in the difference hardly occurs in the entire imaging screen, the entire imaging screen is determined to be the photometric region from the degree of variation in the difference in Patent Document 1. However, at this time, if the ratio of the background to the imaging screen is large, the exposure judgment is pulled by the brightness of the background, and the proper exposure cannot be obtained for the main subject.

From the above problems, the present invention determines the photometric area based on the brightness of the entire imaging screen and the depth of the main subject and the background by using the brightness information in the constant light in addition to the difference information when calculating the photometric area. It is an object of the present invention to provide an image pickup apparatus capable of performing main light emission with an appropriate amount of light.

The invention according to claim 1 is an image pickup apparatus having an image pickup element and a light emitting means, in which the light emitting means pre-emits light prior to the main light emission, and the light emitting means is imaged by the image pickup element when the light emitting means is not emitted. The luminance information acquisition means for acquiring the first luminance information obtained by the above and the second luminance information obtained by imaging the light emitting means with the image pickup element at the time of pre-emission, and the light emission amount of the main light emission are determined. The main emission amount is determined from the photometric results obtained in the calculation area determining means for determining the calculation area used for the calculation and the calculation area used for the calculation for determining the emission amount of the main emission. The calculation area determining means calculates a weighted value based on the luminance from the first luminance information, and from the difference information which is the difference between the first luminance information and the second luminance information. It is characterized in that a weighting value based on the depth of the entire screen is calculated, and a calculation area used for a calculation for determining the light emission amount of the main light emission is calculated based on the weighting value based on the brightness and the weighting value based on the depth. It is an imaging device.

In the invention shown in claim 2, the calculation area determining means calculates a weighting value for high luminance, a weighting value for low luminance, and a mixing ratio of weighting related to luminance from the first luminance information, and obtains the luminance. The imaging apparatus according to claim 1, wherein the result of mixing the weighting value for high brightness and the weighting value for low brightness based on the mixing ratio of the weighting is used as the weighting value based on the brightness. is there.

In the invention shown in claim 3, the calculation area determining means has a weighting value with a depth set so that the larger the difference amount, the larger the weighting, and the smaller the difference amount, the smaller the weighting, and the weighting of the entire screen. The weighting value without depth set to be uniform and the depth amount are calculated from the difference information, and the larger the depth amount, the larger the ratio of using the weighted value with depth and the smaller the depth amount. The imaging apparatus according to claim 1 or 2, wherein the weighting value based on the depth is obtained as a result of being mixed so that the ratio of using the weighting value without depth becomes larger. is there.

In the invention shown in claim 4, the calculation area used for the calculation for determining the amount of light emission of the main emission is a weighted value of the calculation area related to photometry calculated from the weighted value based on the luminance and the weighted value based on the depth. The imaging device according to any one of claims 1 to 3, wherein the region exceeds a predetermined value.

The invention according to claim 5 is a control method of an image pickup apparatus having an image pickup element and a light emitting means and causing the light emitting means to pre-emit light prior to the main light emission, and the light emitting means is imaged when the light emitting means is not emitting light. A step of acquiring the first luminance information obtained by imaging with the element, a step of acquiring the second luminance information obtained by imaging the light emitting means with the imaging element at the time of pre-emission, and the first step. The step of calculating the difference information which is the difference between the brightness information and the second brightness information, the step of calculating the weighting value based on the brightness from the first brightness information, and the depth of the entire screen from the difference information. It is characterized by having a step of calculating a weighted value based on the weight, and a step of calculating a calculation area used for a calculation for determining the amount of light emission of the main emission based on the weighted value based on the brightness and the weighted value based on the depth. This is a control method for an imaging device.

According to the present invention, by using the luminance information in the constant light in addition to the difference information when calculating the photometric region, the photometric region is determined based on the brightness of the entire imaging screen and the depth of the main subject and the background, and the main subject is determined. It is possible to provide an image pickup apparatus capable of performing the main light emission with an appropriate amount of light.

It is a block diagram which shows the main structure of a camera system. It is a schematic diagram which shows the division of the light measurement area of an image data. It is a flow figure explaining the imaging process. It is a flow figure explaining this light emission amount determination. It is a schematic diagram which showed the calculation of the difference information. (1) It is a schematic diagram which shows the brightness in the constant light data. (2) It is a schematic diagram which shows the brightness in the pre-emission data. (3) It is a schematic diagram which shows the difference information. (1) It is a schematic diagram which shows the weighting for high brightness. (2) It is a schematic diagram which shows the weighting for low brightness. It is a schematic diagram which shows the weighting with a depth.

Hereinafter, the best mode for carrying out the present invention will be described with reference to the accompanying drawings. The present invention is not limited to this embodiment.

FIG. 1 is a block diagram showing a main configuration of a camera system according to an embodiment of the present invention. As shown in FIG. 1, this camera system includes an image pickup device 100, an optical device 200, and a light emitting device 300.

The optical device 200 is interchangeable with the image pickup device 100 and includes a lens CPU (not shown). Further, the photographing optical system 210 is composed of a plurality of lens groups (not shown) including a focus lens group and a zoom lens group. In this figure, only one lens is depicted for simplicity.

The image pickup device 100 is a device that is the main body of imaging, and includes an image pickup element 110, a signal processing unit 120, an image display unit 130, a main control unit 140, a luminance information calculation unit 150, and a main emission amount calculation unit 160. , Has a memory unit 170 and a release button 180.

The image sensor 110 is composed of image pixels, receives light rays focused by the photographing optical system 210, performs photoelectric conversion, and outputs them as signal values. A CMOS image sensor is used as the image sensor 110 of the present embodiment. Further, the image sensor 110 of the present embodiment has a built-in gain variable amplifier that amplifies a signal read from a pixel and an A / D converter that digitally converts an analog signal.

The signal processing unit 120 performs normal signal processing on the signal output from each image pickup pixel of the image pickup element 110. The usual signal processing includes dark processing, linearization, and the like, but the description thereof will be omitted because it is the same as the known technique.

The image display unit 130 displays image data processed by the image processing unit 120, image data read from a recording medium (not shown), and the like.

The main control unit 140 performs comprehensive control of the entire image pickup apparatus 100. In this embodiment, a control signal is particularly output to the light emission control unit 310.

The luminance information calculation unit 150 calculates the luminance information for all the signals by performing a known calculation on each signal of the image data. Luminance information is used not only for calculating the amount of light emitted, but also for various processes such as photometry.

The main light emission amount calculation unit 160 calculates the main light emission amount from the brightness information of the image data before and after the pre-light emission. The method of determining the photometric region will be described in detail later.

The memory unit 170 is a member that functions as a buffer for various data, and in this embodiment, particularly records the luminance information of the image data and the difference information calculated by the light emission amount calculation unit 160.

The release button 180 is a kind of user interface. When the user operates the release button 180, the image pickup apparatus 100 takes an image.

The light emitting device 300 is interchangeable with the imaging device 100, and includes a light emitting control unit 310 and a light emitting unit 320. The light emitting control unit 310 receives a control signal from the main control unit 140 to control the light emitting unit 320, and the light emitting unit 320 is controlled by the light emitting control unit 310 to emit light. Here, although the light emitting device 300 is detachable in this embodiment, it may be provided integrally with the image pickup device 100.

Further, the image pickup apparatus 100 in this embodiment is equipped with a through image shooting mode. The through image shooting mode is a kind of still image shooting mode, and is a mode in which signals are continuously read from the image sensor 110 until the still image shooting is performed, and displayed as image data on the image display unit 130. Since the through image shooting mode is a known technique, it will be omitted in detail.

Next, the photometric method in this embodiment will be described. FIG. 2 is a schematic view showing division of a light measuring region of image data according to an embodiment of the present invention. In this embodiment, as shown in FIG. 2, the image data is divided into several areas for photometric measurement. The luminance information calculation unit 150 calculates the luminance information of each area by averaging the luminance information calculated from the individual pixels for each of the divided areas. By dividing the photometric area in this way, it is possible to shorten the time required for calculating the luminance information of the image data, which is advantageous in the continuous luminance information calculation in through image shooting and the like. Here, the divided individual areas are referred to as divided metering areas. Further, the number of divided image data and the size of the divided photometric area may be appropriately selected according to the convenience of the practitioner.

Next, a general imaging process of the camera system in this embodiment will be described. FIG. 3 is a flow chart illustrating an imaging process according to an embodiment of the present invention.

When a command for the through image shooting mode is transmitted from the main control unit 140 in step S101, the through image shooting is performed in step S102. In the through image shooting mode, the image sensor 110 is continuously driven, and the signal output from the image sensor 110 is processed by the signal processing unit 120 and displayed on the image display unit 130, and is also used as data related to photometric measurement. Etc.

In step S103, it is determined whether or not the release button 180 has been operated in the through image shooting mode. If the release button 180 is operated, it is determined that the release is ON, and the process proceeds to step S104. If the release button 180 is not operated, the process returns to immediately after step S101.

In step S104, the luminance information calculation unit 150 calculates the luminance information in the through image when the flash does not emit light when the release is turned on, and stores the luminance information in the memory unit 170 as the luminance information in the constant light. Further, the through image when the flash does not emit light when the release is turned on is referred to as constant light data.

In step S105, the main control unit 140 instructs the light emitting unit 320 to perform pre-light emission at a predetermined intensity, and pre-light emission is performed. In this embodiment, the amount of pre-emission is a fixed value regardless of the conditions, but it may be calculated based on the luminance information calculated in step S104.

In step S106, the luminance information calculation unit 150 calculates the brightness in the through image at the time of pre-emission, and stores it in the memory unit 170 as the luminance information in the pre-emission. Further, the through image at the time of pre-flash is referred to as pre-flash data.

In step S107, the main emission amount calculation unit 160 calculates the main emission amount from the luminance information in the constant light and the luminance information in the pre-emission. The calculation of this light emission amount will be described in detail later.

In step S108, the main control unit 140 instructs the light emission control unit 310 to perform the main light emission at the light emission amount calculated by the main light emission amount calculation unit 160, and the light emission control unit 310 controls the light emission unit 320. Light is emitted.

In step S109, the main control unit 140 takes an image, the image data obtained by the image taking is recorded in a memory card (not shown), and this flow diagram ends in S110.

The above is the general imaging process in this embodiment. Next, the method for determining the amount of emitted light, which is performed in step S107, will be described. FIG. 4 is a flow chart illustrating the determination of the amount of light emitted according to the embodiment of the present invention. Further, the determination of the main emission amount is performed by the main emission amount calculation unit 160.

When the main control unit 140 gives an instruction to start the main emission amount calculation in step S201, the difference information is calculated in step S202.

The difference information is calculated by calculating the difference between the luminance information in the constant light data acquired in step S104 and the luminance information in the pre-emission data acquired in step S106. FIG. 5 is a schematic diagram showing the calculation of the difference information. FIG. 5 (1) shows the luminance information in the constant light data, FIG. 5 (2) shows the luminance information in the pre-emission data, and FIG. 5 (3) shows the difference information. For these divided photometric regions, the difference information is acquired by associating the brightness information in the constant light data with the brightness information in the pre-emission data and calculating the difference amount.

In steps S203 to S206, the photometric region used for the calculation for determining the light emission amount of the main light emission is calculated. In order to calculate the appropriate amount of light emission, it is necessary to determine an appropriate photometric area from the entire imaging screen. The metering area is determined by weighting the divided photometric areas and calculating the weighting value for each area. In step S203, the weighting value based on the brightness is calculated from the constant light data, and in step S204, the weighting value based on the depth is calculated from the difference information. In step S205, the weighting value related to metering is calculated by integrating those weighting values, and in step S206, the measurement area related to the main light emission is obtained by selecting the necessary area and the unnecessary area from the weighting value related to metering. It is determined. The above process will be described in order.

In step S203, weighting based on brightness is performed. The weighting based on the brightness is a weighting for calculating the photometric region by evaluating the brightness of the constant light data that cannot be obtained only by the difference information when determining the light amount of the main emission.

Here, a method of obtaining a photometric region in an environment where constant light is relatively bright will be described. For example, when there is a difference in brightness between the background and the main subject in an environment such as outdoors where the background is relatively bright, and the background occupies a large proportion of the entire imaging screen, the image data has high brightness as a whole. In that case, if photometry is performed from the entire imaging screen, the photometric result depends on the high-luminance region. Therefore, if the amount of light of the main emission is determined using the photometric result of the entire photometric region, the amount of light is sufficient for the high-luminance region, but the amount of light is insufficient for the low-luminance region. .. Therefore, when the image data has high brightness as a whole, an appropriate photometric area can be obtained by using the high-luminance weighting in which the lower the brightness is, the higher the weight is, and the higher the brightness is, the lower the weight is set. Can be decided.

FIG. 6 (1) is a schematic diagram showing weighting for high brightness. The numbers shown in the figure are the luminance values detected for each divided metering area. The shaded area indicates a low-weighted area, and the other areas indicate a high-weighted area. As shown in the figure, in the weighting for high luminance, the weighting is set high in the region having low luminance, and the weighting is set low in the region having high luminance.

Further, the weighting value for high brightness in each divided photometric region is calculated by applying the formula for high brightness weighting stored in advance in the main emission amount calculation unit 160 to the brightness information in the constant light.

On the other hand, if there is a difference in brightness between the background and the main subject in an environment where the constant light is relatively dark, such as indoors, and the background occupies a large proportion of the entire imaging screen, the image data as a whole has low brightness. , The photometric result depends on the low brightness region. Therefore, when the image data has low brightness as a whole, an appropriate photometric region can be determined by using the weighting for low brightness in which the weighting is set higher as the brightness is higher.

FIG. 6 (2) is a schematic diagram showing weighting for low brightness. As shown in the figure, the weighting for low luminance is set to be low in the low-luminance region and high in the high-luminance region.

Further, the weighting value for low brightness in each divided photometric region is calculated by applying the formula for low brightness weighting stored in advance in the main emission amount calculation unit 160 to the brightness information in the constant light.

In this embodiment, an appropriate photometric region based on the brightness is determined by mixing the weighting for high brightness and the weighting for low brightness according to the brightness of the constant light. The weighting is mixed by mixing the weighting values in each divided photometric region at a ratio corresponding to the brightness of the constant light.

The brightness of the constant light is calculated from the brightness information in the constant light. In this embodiment, the brightness of the constant light is calculated by averaging the brightness information of all the photometric regions. Here, the brightness of the constant light may be evaluated by a different method such as using the median value of the histogram.

The calculated brightness of the constant light is standardized by the dynamic range which is the vertical width of the brightness, and is calculated by a value of 0 or more and 1 or less as the mixing ratio of the weighting related to the brightness. As for the mixing ratio of the weights related to the brightness, the higher the brightness of the constant light, the larger the ratio of using the weight value for high brightness, and the lower the brightness of the constant light, the larger the ratio of using the weight value for low brightness. Is calculated to be.

Further, in a predetermined divided metering region, if the weighting value based on the brightness is LW, the weighting value for high brightness is LWH, the weighting value for low brightness is LWL, and the mixing ratio of the weighting related to brightness is LR, the weighting based on brightness is defined. The value is expressed by the following formula.

As described above, the weighting value based on the brightness is calculated for all the divided photometric regions. Subsequently, in step S204, weighting based on the depth is performed. The weighting based on the depth is a weighting calculated from the difference information, and is a weighting for evaluating the depth of the entire imaging screen and calculating the photometric region when determining the amount of light of the main emission.

As for the appropriate light measurement area based on the depth, if there is depth, only the subject with a large difference is used as the light measurement area, while if there is no depth, the entire imaging screen is used as the light measurement area to obtain appropriate exposure related to the depth. Can be obtained. Therefore, weighting based on depth is performed by mixing the weighting with depth, which is set to have a high weighting for a subject with a large difference amount, and the weighting without depth, which is set to be uniformly weighted for the entire imaging screen, according to the amount of depth. Is calculated.

By setting in this way, it is possible to determine whether the background or the main subject is used, and as a result, it is possible to increase the weighting of the main subject.

FIG. 7 is a schematic view showing weighting with depth. The numbers shown in the figure are the difference amounts calculated for each divided metering area. The shaded area indicates a low-weighted area, and the other areas indicate a high-weighted area. As shown in the figure, in the weighting with depth, the weighting is set low in the region where the difference amount is small, and the weighting is set high in the region where the difference amount is large. On the other hand, in the weighting without depth, the same weighting is set for all the divided metering areas.

The weighting value with depth is calculated by applying the weighting formula with depth stored in advance in the light emission amount calculation unit to the difference information. On the other hand, the weighted value without depth is stored in the main emission amount calculation unit 160 in advance, and is called in step S204.

The depth amount is calculated from the difference information. In this embodiment, the difference obtained by subtracting the maximum value and the minimum value of the difference amount in the difference information is the depth amount. Here, the depth amount may be evaluated by a different method such as using the median value of the histogram of the difference information.

The calculated depth amount is standardized by dividing by a constant, and is calculated with a value of 0 or more and 1 or less as a mixing ratio of weighting related to depth. The mixing ratio of weighting related to depth is calculated so that the larger the depth, the larger the ratio of using the weighted value with depth, and the smaller the depth, the larger the ratio of using the weighted value without depth. Further, the constant related to division is a value preset as a numerical value related to determination of depth and stored in the main emission amount calculation unit 160, and may be determined within a range required by the practitioner.

Further, in a predetermined divided metering region, if the weighting value based on the depth is DW, the weighting value with depth is DWH, the weighting value without depth is DWL, and the weighting value related to depth is DR, the weighting value based on depth is as follows. It is represented by an expression.

As described above, the weighting value based on the depth is calculated for all the divided photometric regions. Subsequently, in step S205, the weighting related to the light measurement for determining the light measuring region related to the main light emission is calculated. The weighting related to photometry is calculated by integrating the weighting based on the brightness calculated in step S203 and the weighting based on the depth calculated in step S204. Here, assuming that the weighting value related to metering is W, the weighting value related to metering is expressed by the following equation.

In step S206, the photometric region related to the main light emission is determined. That is, the divided photometric region in which the weighting value related to photometry is equal to or greater than a predetermined value is determined as the photometric region related to the main emission. Here, the predetermined value may be determined as necessary so that the light measurement result desired by the practitioner can be obtained.

In step S207, the main emission amount is calculated based on the photometric region determined in step S206, and the flow chart ends in step S208.

According to the above embodiment, the photometric region based on the brightness can be calculated in addition to the depth. As a result, even when the difference information due to the pre-emission cannot be obtained, it is possible to detect the main subject and perform the main emission with an appropriate amount of light.

Further, by calculating the photometric region based on the brightness from the weighting for high brightness and the weighting for low brightness, it is possible to determine the brightness of the entire imaging screen, which cannot be determined only by the difference information. Therefore, even when there is no depth and the brightness difference between the background and the main subject is large, it is possible to emit light with an appropriate amount of light.

In this embodiment, the luminance information is acquired in the through image shooting mode, but any form may be used as long as it is possible to acquire the luminance information related to photometry, such as by providing a dedicated photometric sensor.

As described above, according to the imaging device 100 of the present invention, the brightness of the entire imaging screen and the depth of the main subject and the background are used by using the luminance information in the constant light in addition to the difference information when calculating the photometric region. It is possible to provide an image pickup apparatus 100 capable of determining a photometric region based on the above and performing main light emission to a main subject with an appropriate amount of light.

100 Image sensor 110 Image sensor 120 Signal processing unit 130 Image display unit 140 Main control unit 150 Luminance information calculation unit 160 Luminance amount calculation unit 170 Memory unit 180 Release button 200 Optical device 210 Photographic system 300 Light emitting device 310 Light emission control unit 320 Light emitting part

Claims (5)

It has an image sensor and a light emitting means.
An imaging device that pre-emits the light emitting means prior to the main light emission.
Luminance to acquire the first luminance information obtained by imaging the light emitting means by the image sensor when the light emitting means is non-luminous and the second luminance information obtained by imaging the light emitting means by the image sensor when the light emitting means is pre-flashed Information acquisition means and
An arithmetic area determining means for determining an arithmetic area used for an operation for determining the amount of light emitted from the main emission,
From the photometric results obtained in the calculation area used for the calculation for determining the emission amount of the main emission.
It has a main emission amount determining means for determining the emission amount of the main emission.
The calculation area determining means calculates a weighted value based on the brightness from the first brightness information, and obtains a weighted value based on the brightness.
A weighting value based on the depth of the entire screen is calculated from the difference information which is the difference between the first luminance information and the second luminance information.
An imaging device characterized in that a calculation area used for a calculation for determining the amount of light emission of the main light emission is calculated based on the weighting value based on the brightness and the weighting value based on the depth. The calculation area determining means calculates a weighting value for high luminance, a weighting value for low luminance, and a mixing ratio of weighting related to luminance from the first luminance information.
The first aspect of claim 1, wherein the result of mixing the weighting value for high brightness and the weighting value for low brightness based on the mixing ratio of the weighting related to the brightness is used as the weighting value based on the brightness. Imaging device. The calculation area determining means has a weighted value with a depth set so that the larger the difference amount is, the larger the weight is, and the smaller the difference amount is, the smaller the weight is. Calculate the weighting value of none and the depth amount from the difference information,
The larger the depth amount, the larger the ratio of using the weighted value with the depth, and the smaller the depth amount, the larger the ratio of using the weighted value without the depth. The imaging apparatus according to claim 1 or 2, wherein the value is used. The calculation area used for the calculation for determining the amount of light emission of the main light emission is a region in which the weighting value of the calculation area related to photometry calculated from the weighting value based on the brightness and the weighting value based on the depth exceeds a predetermined value. The imaging apparatus according to any one of claims 1 to 3, wherein the image pickup apparatus is provided. It has an image sensor and a light emitting means.
It is a control method of an image pickup apparatus which pre-emits the light emitting means prior to the main light emission.
A step of acquiring the first luminance information obtained by imaging the light emitting means with the image sensor when the light emitting means is not emitting light, and
A step of acquiring the second luminance information obtained by imaging the light emitting means with the image sensor at the time of pre-light emission, and
The step of calculating the difference information which is the difference between the first luminance information and the second luminance information, and
A step of calculating a weighting value based on the brightness from the first brightness information, and
A process of calculating a weighted value based on the depth of the entire screen from the difference information, and
A control method for an image pickup apparatus, comprising: a step of calculating a calculation area used for a calculation for determining a light emission amount of the main emission based on a weighting value based on the brightness and a weighting value based on the depth.

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