JP2008129027A - Backlight determination device, image taking device, backlight determination method, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform an appropriate backlight determination of an image taken with an image taking device by limited backlight patterns. <P>SOLUTION: An image acquisition part 210 acquires an image taken and separates a high luminance area and a low luminance area from the image area of the image taken. A backlight area extraction part 220 extracts a backlight area from the separated low luminance area using limited backlight patterns. A light intensity ratio calculation part 230 calculates a proportion of an average luminance value of the extracted backlight area to an average luminance value of the separated high luminance area as a light intensity ratio X. A backlight degree calculation part 240 calculates a degree of backlight that represents a degree of the backlight state based on the calculated light intensity ratio. A correction factor calculation part 260 calculates a correction factor based on the amount of exposure in the image taking environment. A backlight degree correction part 270 corrects the degree of backlight based on the degree of backlight and the correction factor. A backlight state determination part 280 determines whether the image taken is in the backlight state by comparing the corrected backlight degree with the threshold value of the backlight determination. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an imaging apparatus, and more particularly to a backlight discrimination apparatus that discriminates whether or not a captured image is in a backlight state, a processing method therefor, and a program that causes a computer to execute the method.

  2. Description of the Related Art Conventionally, in an imaging device, when a captured image is in a backlight state, processing for acquiring an appropriate captured image by strobe light emission or exposure correction is performed. At this time, as a method of determining whether or not the captured image is in the backlight state, there is a method of determining from the tendency of the histogram indicating the distribution of the number of pixels for each luminance value. In this histogram, if there is a tendency that the number of pixels having a bright luminance value and a dark luminance value increases, it can be determined that there is a high possibility of being in a backlight state.

  As another discrimination method, by measuring the luminance value on the captured image, the backlight region is separated from the normal region which is the other region by the backlight pattern which is the arrangement of the backlight region, and the backlight region and the normal region are separated. There is also a method of determining that there is a high possibility of being in a backlight state if the difference in average luminance value is large.

In addition, a discrimination method using a combination of the above two discrimination methods has also been proposed. For example, in a histogram, the luminance distribution area is separated into a high luminance area, a medium luminance area, and a low luminance area, and the distribution tendency of the number of pixels corresponding to each area is used, and the backlight area separated from the backlight pattern and the normal area There has been proposed a system for determining whether or not a backlight is in a backlight state by using a ratio of average luminance values of regions (see, for example, Patent Document 1).
Japanese Patent Laying-Open No. 2004-235958 (FIG. 1)

  In the above-described prior art, since the backlight state is various, it is necessary to hold a large number of backlight patterns in order to determine the backlight. In addition, as the number of backlight patterns increases, the time for backlight discrimination increases. On the other hand, no matter how many backlight patterns are provided, it is not determined that the backlight state is in the backlight state when the backlight state is an arrangement of a backlight region that does not exist in the prescribed backlight pattern. Also, if the backlight is determined only from the histogram, the backlight determination is different due to the variation in the exposure amount of the imaging environment, and the backlight state of the subject cannot be determined accurately.

  Accordingly, an object of the present invention is to make an appropriate backlight determination based on a limited backlight pattern in a captured image.

  The present invention has been made in order to solve the above problems, and a first aspect of the present invention is an image acquisition unit that acquires a captured image and separates it into at least two regions, a high-luminance region and a low-luminance region, A backlight region extracting means for searching for a region where the average value of the luminance value is lowest with respect to a predetermined backlight pattern in the low luminance region and extracting it as a backlight region; an average value of the luminance value in the high luminance region and the backlight A light amount ratio calculating means for calculating a ratio of an average value of luminance values in a region as a light amount ratio, a reverse light intensity calculating means for calculating a backlight intensity based on the light amount ratio, and the backlight intensity exceeding a predetermined threshold And a backlight state determining means for determining that the backlight is in the backlight state. As a result, the backlight region is extracted from the low-brightness region of the captured image, and it is determined whether or not the backlight state is based on the ratio of the average value of the luminance value in the high-brightness region of the captured image and the average value of the luminance value in the backlight region. It brings about the effect of letting.

  In the first aspect, the backlight intensity calculating means calculates the backlight intensity as an after event of the light amount ratio. Accordingly, there is an effect that the backlight state of the captured image is determined based on the backlight intensity indicating how much the brightness value is insufficient with respect to the state where the brightness value is uniform and there is no backlight state at all.

  In the first aspect, the image acquisition means sets a predetermined area above the captured image as the high luminance area and a predetermined area below the captured image as the low luminance area. And This brings about the effect | action that a picked-up image is isolate | separated into the area | region where a luminance value is statistically high and the area | region where a luminance value is statistically low.

  Further, in the first aspect, the apparatus further includes a backlight determination holding unit that stores a determination result as to whether or not the backlight state is determined as a result of the determination in the backlight state determination unit, and the backlight state determination unit includes: When the determination result is the backlight state, the predetermined threshold value is changed to a lower value. This brings about the effect that the threshold value used for the determination of the backlight state is changed based on the imaging state of the previous frame.

  Further, in the first aspect, the image acquisition means has a first arrangement in which a predetermined area above the captured image is the high luminance area and a predetermined area below the captured image is the low luminance area. A second arrangement in which a predetermined region on the left side of the captured image is the high luminance region and a predetermined region on the right side of the captured image is the low luminance region; and a predetermined region on the right side of the captured image The backlight intensity calculating means is configured to separate each of at least three areas from the third arrangement in which the area is the high-luminance area and the predetermined area on the left side of the captured image is the low-luminance area. Among the three arrangements, the one having the highest calculated backlight intensity is determined as a correct arrangement, and the backlight intensity of the arrangement is output. Thereby, the effect of determining the imaging direction of the imaging device and determining the backlight state with respect to the imaging direction is brought about.

  Further, in the first aspect, an exposure amount acquisition unit that acquires an exposure amount when the captured image is captured, and a correction that calculates the necessity of correcting the backlight intensity based on the exposure amount as a correction rate The apparatus further comprises a rate calculating means and a backlight intensity correcting means for correcting the backlight intensity based on the correction factor. This brings about the effect that the backlight state is determined based on the corrected backlight intensity adapted to the exposure amount of the imaging environment.

  According to a second aspect of the present invention, there is provided an imaging unit that images a subject and generates a captured image, and an image acquisition unit that acquires the captured image and separates the captured image into at least two regions of a high luminance region and a low luminance region. And a backlight region extracting means for searching for a region where the average value of the luminance value is lowest with respect to a predetermined backlight pattern in the low luminance region and extracting it as a backlight region, and an average value of the luminance values in the high luminance region, A light intensity ratio calculating means for calculating a ratio of an average value of luminance values in the backlight area as a light intensity ratio; a backlight intensity calculating means for calculating a backlight intensity based on the light intensity ratio; and the backlight intensity exceeding a predetermined threshold value. An imaging apparatus comprising: a backlight state determination unit that determines that the backlight is in a backlight state. As a result, a backlight region is extracted from the low-brightness region of the captured image, and whether or not the backlight state is based on the ratio of the average luminance value in the high-brightness region and the average luminance value in the backlight region of the captured image. It brings about the effect of making it judge.

  The third aspect of the present invention is a backlight region extraction procedure for searching for a region where the average value of the luminance value is lowest with respect to a predetermined backlight pattern in the low luminance region and extracting it as a backlight region, A light amount ratio calculating procedure for calculating a ratio of the average value of the luminance values in the luminance region and the average value of the luminance values in the backlight region as a light amount ratio; a backlight intensity calculating procedure for calculating the backlight intensity based on the light amount ratio; A backlight discrimination method comprising determining a backlight condition when the backlight intensity exceeds a predetermined threshold, or a program for causing a computer to execute the procedure is there. As a result, the backlight region is extracted from the low-brightness region of the captured image, and it is determined whether or not the backlight state is based on the ratio of the average value of the luminance value in the high-brightness region of the captured image and the average value of the luminance value in the backlight region. It brings about the effect of letting.

  According to the present invention, it is possible to achieve an excellent effect that an appropriate backlight determination can be made with a limited backlight pattern in a captured image.

  Next, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram illustrating a functional configuration example of an imaging apparatus 100 according to an embodiment of the present invention.

  The imaging apparatus 100 includes a lens unit 110, an image sensor 120, an analog signal processing unit 130, a digital signal processing unit 140, a display unit 150, a lens control unit 160, a timing generator 170, and a system control unit 180. And a strobe 190 and an imaging operation accepting unit 200.

  The lens unit 110 collects light of the subject and forms an optical image of the subject on the image sensor 120. Further, the lens unit 110 adjusts the amount of incident light by adjusting the aperture value, adjusting the shutter speed, or the like based on the control from the lens control unit 160.

  The image sensor 120 converts an optical image formed by the lens unit 110 into an electrical signal and outputs it as an analog video signal. As the image sensor 120, for example, a CCD sensor (Charge Coupled Device Sensor) or the like is used.

  The analog signal processing unit 130 converts the analog video signal output from the image sensor 120 into a digital video signal by an A / D converter (Analog to Digital converter). In addition, the analog signal processing unit 130 removes reset noise and the like included in the analog video signal output from the image sensor 120 with an S / H (Sample and Hold) circuit or the like. Further, the analog signal processing unit 130 adjusts the gain of the analog video signal by AGC (Automatic Gain Control) based on the control from the system control unit 180.

  The digital signal processing unit 140 performs appropriate signal processing on the digital video signal output from the analog signal processing unit 130 and outputs a luminance signal and a color difference signal to the display unit 150. Further, the digital signal processing unit 140 outputs a captured image necessary for determining the backlight state to the system control unit 180.

  The display unit 150 displays an image by performing predetermined signal processing such as gamma correction and contrast correction based on the luminance signal and the color difference signal output from the digital signal processing unit 140.

  The lens control unit 160 performs control such as aperture value adjustment and shutter speed adjustment of the lens unit 110 based on the control from the system control unit 180. Thereby, the lens unit 110 is controlled so that an appropriate exposure correction process is performed on the captured image in the backlight state.

  The timing generator 170 supplies various drive pulses on the horizontal axis and the vertical axis necessary for driving the image sensor 120 to the image sensor 120, and generates reference pulses necessary for synchronizing the processing of the image sensor 120 and the analog signal processing unit 130. This is supplied to the image sensor 120.

  The system control unit 180 determines whether the captured image is in a backlight state, and based on the determination result, the analog signal processing unit 130, the digital signal processing unit 140, the display unit 150, the lens control unit 160, a timing generator. 170, control of the respective units such as the strobe 190 and the imaging operation receiving unit 200, and overall control. Further, the system control unit 180 has various functions for determining whether or not the captured image is in a backlight state.

  The strobe 190 emits light to irradiate the subject with light based on the control from the system control unit 180. By the light emission of the strobe 190, the luminance value of the backlight region in the captured image increases, and the backlight state is improved.

  The imaging operation reception unit 200 receives an imaging operation instruction and is realized by, for example, a shutter button. In synchronization with this imaging operation instruction, the flash 190 emits light, performs an imaging operation, and the like.

    Next, determination of the backlight state in the embodiment of the present invention will be described with reference to the drawings.

  FIG. 2 is a block diagram illustrating a functional configuration example of backlight determination by the system control unit 180 according to the embodiment of the present invention.

  The system control unit 180 includes an image acquisition unit 210, a backlight region extraction unit 220, a light amount ratio calculation unit 230, a backlight intensity calculation unit 240, an exposure amount acquisition unit 250, a correction factor calculation unit 260, and backlight intensity correction. Unit 270, backlight state determination unit 280, and backlight determination holding unit 290.

  The image acquisition unit 210 acquires a captured image from the digital signal processing unit 140 and separates the captured image into at least two regions, a high luminance region and a low luminance region [0]. Here, the high luminance region is defined in the upper part in the assumed arrangement (image direction). Further, the low luminance region is defined in the lower part in the assumed arrangement (image direction). A region that does not correspond to either the high luminance region or the low luminance region may exist in the captured image. This separation is performed in three directions in order to determine in which imaging direction the captured image is captured. Further, the image acquisition unit 210 outputs the image of the high brightness area in the captured image to the light amount ratio calculation unit 230 and outputs the image of the high brightness area in the captured image to the backlight area extraction unit 220.

  The backlight region extraction unit 220 searches for a region where the average luminance value is the lowest with respect to the backlight pattern in the image of the low luminance region supplied from the image acquisition unit 210 and extracts it as a backlight region [ 0]. During this search, the backlight pattern is sequentially moved in the low luminance region in the captured image, and the average luminance value at each position is measured. Note that the extraction of the backlight region is performed for each of the above-described arrangements in the three directions.

  The light amount ratio calculation unit 230 calculates a ratio between the high luminance region separated by the image acquisition unit 210 and the average luminance value of the backlight region extracted by the backlight region extraction unit 220 as the light amount ratio X. As a result, the ratio between the region with a high average luminance value on the captured image and the portion with a low average luminance value is calculated. The calculation of the light amount ratio X is performed for each of the above-described arrangements in the three directions.

  The backlight intensity calculator 240 calculates the backlight intensity J1 that is the degree of the backlight state based on the light intensity ratio X calculated by the light intensity ratio calculator 230. Further, the calculation of the backlight intensity J1 is performed for each of the arrangements in the three directions described above, and the one with the highest calculated backlight intensity is determined as the correct layout. The backlight intensity J1 is calculated by subtracting the light amount ratio X1 from the light amount ratio (100%) when it is assumed that the luminance value on the captured image is uniform. That is, the backlight intensity J1 is calculated as an after event of the light quantity ratio X1. Thereby, the backlight intensity JI indicating how much the brightness value is insufficient with respect to the state where the brightness value is uniform and there is no backlight state at all is calculated.

The exposure amount acquisition unit 250 acquires the exposure amount from the shutter speed, the aperture value, the brightness of the captured image, and the like. This exposure amount indicates the brightness of the imaging environment and can be expressed in units of EV (Exposure Value). This is because the exposure value when the aperture value is F1.0 in the imaging apparatus 100 and the shutter speed is 1 second is defined as 0 EV, and from there, 1 EV each time the aperture value or shutter speed increases by one step. It is defined as an increase. For example, when the ISO sensitivity of the imaging apparatus 100 is 100, the brightness of the room is about 5 EV, the brightness of the evening is about 7 EV, and the brightness of the clear sky is about 17 EV. Here, when the aperture value is AV, the shutter speed is TV, the gain amount of AGC is SV, and the amount of light incident on the lens unit 110 is BV, the exposure amount EV is calculated by the following equation.
EV = AV + TV + SV + BV

  The correction rate calculation unit 260 calculates a correction rate J2 indicating the degree of necessity for correction of the backlight intensity J1 calculated by the backlight intensity calculator 240. Since the backlight intensity J1 needs to be corrected depending on the exposure amount in the imaging environment, the correction factor J2 is calculated based on the exposure amount acquired by the exposure amount acquisition unit 250.

  The backlight intensity correction unit 270 corrects the backlight intensity J1 calculated by the backlight intensity calculator 240 based on the correction factor J2 calculated by the correction factor calculator 260. That is, the corrected backlight intensity R0, which is the corrected backlight intensity, is calculated by multiplying the backlight intensity J1 by the correction factor J2 [0].

  The backlight state determination unit 280 compares the corrected backlight intensity R0 calculated by the backlight intensity correction unit 270 with the threshold value R of the backlight state, and determines that the backlight state is in the backlight state if the backlight intensity exceeds a predetermined threshold value R. The result of this determination is output. The threshold value R of the backlight state is changed to a lower value when the captured image performed one frame before is in the backlight state. Note that the determination result of whether or not the previous frame was in the backlight state is held in the backlight determination holding unit 290.

  The backlight determination holding unit 290 holds the result of the backlight state determination output from the backlight state determination unit 280. The determination result held in the backlight determination holding unit 290 is referred to when the backlight state determination unit 280 determines the next frame.

  FIG. 3 is a diagram illustrating an example in which a captured image according to the embodiment of the present invention is separated into a high luminance region 330 and a low luminance region 340.

  FIG. 3A is a diagram illustrating an example in which an imaging region 300 that is a region of a captured image of the subject 310 is divided into blocks 320 having a predetermined area. In this example, the imaging region 300 is divided into seven parts in the vertical direction and the horizontal direction, and is divided into blocks 320 that are units of measurement of luminance values.

  FIG. 3B is a diagram in which the captured image is separated into a high luminance region 330 and a low luminance region 340. In this example, the upper part of the imaging region 300 is separated as a high luminance region 330 and the lower part of the imaging region 300 is separated as a low luminance region 340. The reason for such separation is that, according to the statistics of the captured image indicating the backlight state, there is a tendency that a region with a high luminance value exists above the imaging region 300 and a region with a low luminance value exists below the imaging region 300. Because. For example, it is assumed that the sun as a light source is at a high position in the daytime and the subject 310 is standing with the sun behind. In this case, the luminance value is high because the upper part of the imaging region 300 is the sun of the light source, and the luminance value is low because a shadow is formed in the lower part of the imaging region 300.

  However, even if the imaging region 300 is separated into the high luminance region 330 and the low luminance region 340 in this way, when the imaging direction of the imaging device 100 changes, it is necessary to perform separation that matches the imaging direction. Therefore, in the embodiment of the present invention, in order to determine in which imaging direction the captured image is captured, from the imaging region 300 to the high luminance region 330 and the low luminance with respect to the arrangement in three directions (image direction). Isolate region 340.

  FIG. 4 is a diagram showing a procedure for extracting a backlight region from the low luminance region 340 by the backlight region extraction unit 220 according to the embodiment of the present invention.

  FIG. 4A is a diagram showing a backlight pattern 350 in the embodiment of the present invention. The backlight pattern 350 is for indicating the position of the backlight region in the captured image. By using the backlight pattern 350, the average luminance value of the low luminance region 340 is sequentially measured. The backlight pattern 350 is determined with a size of about 10% to 30% of the imaging region 300. When the size of the backlight pattern 350 is less than 10% of the size of the imaging region 300, the measured average luminance value fluctuates to increase false detection, and conversely, the size of the backlight pattern 350 is the imaging region 300. If it exceeds 30% of the size, there is a possibility that the backlight region becomes wide and the backlight region cannot be extracted accurately. In this example, the backlight pattern 350 includes three blocks 320 in the vertical direction and the horizontal direction, respectively.

  FIGS. 4B to 4F are diagrams showing the arrangement of the backlight pattern 350 when the backlight pattern 350 sequentially measures the low-luminance region 340. FIG.

  In the backlight pattern 350, the average luminance value is sequentially measured by moving the block 320 one by one from the left side of the low luminance region 340 to the right side. At that time, the subject 310 is located on the right side from the center of the imaging region 300. Therefore, the backlight pattern 350 is expected to have the lowest average luminance value at the position of the backlight pattern 350 in FIG. 4E or FIG. As described above, the backlight region extraction unit 220 extracts the region where the average value of the luminance values is the lowest in the low luminance region 340 by the arrangement of the backlight pattern 350.

  FIG. 5 is a diagram illustrating an imaging direction detection method performed by the backlight intensity calculation unit 240 according to the embodiment of the present invention.

  FIG. 5A shows the arrangement of the high luminance region 330 and the backlight region 360 when the imaging direction is the horizontal direction. As described above, when the imaging direction is the horizontal direction, the high luminance area 330 is located at the upper position of the imaging area 300, and the backlight area 360 is located below the imaging area 300.

  FIG. 5B shows the arrangement of the high luminance region 330 and the backlight region 360 when the imaging apparatus 100 is rotated 90 degrees to the right and the imaging direction becomes the vertical direction. As described above, when the image is picked up by the right rotation, the high luminance region 330 is located at the left position of the image pickup region 300 and the backlight region 360 is located at the right portion of the image pickup region 300.

  FIG. 5C shows the arrangement of the high luminance area 330 and the backlight area 360 when the imaging apparatus 100 is rotated 90 degrees counterclockwise and the imaging direction becomes the vertical direction. As described above, when the image is picked up by the left rotation, the high luminance region 330 is located at the right position of the image pickup region 300 and the backlight region 360 is located at the left portion of the image pickup region 300.

  The backlight intensity calculator 240 calculates the backlight intensity J1 from the average brightness values of the high brightness area 330 and the backlight area 360 in each imaging direction. As a result, among the three arrangements (image directions), the one with the highest calculated backlight intensity J1 is determined as the correct arrangement. For example, in this example, the horizontal arrangement is determined as the correct arrangement as shown in FIG.

  FIG. 6 is a diagram showing an example of a method for calculating the correction factor J2 by the correction factor calculator 260 in the embodiment of the present invention.

  Here, the exposure amount of the imaging environment is shown in the horizontal axis direction, and the correction factor J2 is shown in the vertical axis direction. Using this relationship, the correction rate calculation unit 260 calculates the correction rate J2 from the exposure amount acquired by the exposure amount acquisition unit 250.

  When the exposure amount is EVs or less, the correction rate J2 is 0%, and when the exposure amount is EVe or more, the correction rate J2 is 100%. Here, EVs is the exposure amount at the boundary where the correction factor J2 of the backlight intensity J1 starts to fluctuate. The correction factor J2 is 0% until the exposure amount exceeds EVs, and therefore the backlight intensity J1 is a constant value “0”. Indicates. Further, EVe is the exposure amount at the boundary where the correction of the backlight intensity J1 is unnecessary, and means that the correction of the backlight intensity J1 is unnecessary when the exposure amount exceeds EVe. This EVe is set with an evening scene as a guide. When the exposure amount shows a value between EVs and EVe, the correction factor J2 increases corresponding to the exposure amount. Here, an example of increasing linearly is shown, but the present invention is not limited to this.

  This correction is performed to remove the influence of the backlight intensity J1 due to the brightness of the imaging environment. In addition, this correction can prevent the determination result in the backlight state determination unit 280 from continuously switching (hunting).

  FIG. 7 is a diagram showing a change in threshold value used for determination of the backlight state by the backlight state determination unit 280 in the embodiment of the present invention. 7A to 7C, the horizontal axis represents frame numbers indicating the order of imaging operations, and the vertical axis represents backlight intensity R, backlight determination threshold value R0, and backlight determination result, respectively. Here, when it is determined that the backlight is not in the back-lighting state during the previous imaging operation, the backlight determination threshold value R0 is set to 80%, and it is determined that the backlight is in the back-lighting state during the previous imaging operation. In this case, it is assumed that the backlight determination threshold value R0 is set to [0] at 70%. Thereby, together with the above-described correction, the determination result of the backlight state is prevented from being switched continuously (hunting).

  First, when the frame number is “1”, the backlight R is less than 70%, whereas the backlight determination threshold R0 is 80%. Therefore, the backlight state determination unit 280 determines that the backlight state is not the backlight state because the backlight intensity R does not exceed the backlight determination threshold value R0.

  Next, when the frame number is “2”, the backlight R is 70% or more but less than 80%, whereas the backlight determination threshold R0 is 80%. Therefore, the backlight state determination unit 280 determines that the backlight state is not the backlight state because the backlight intensity R does not exceed the backlight determination threshold value R0.

  Next, when the frame number is “3”, the backlight intensity R exceeds 70%, while the backlight determination threshold value R0 is 80%. Therefore, the backlight state determination unit 280 determines that the backlight state is in the backlight state because the backlight intensity R exceeds the backlight determination threshold value R0.

  Next, when the frame number is “4”, the backlight intensity R exceeds 70% but is less than 80%. At that time, the backlight state determination unit 280 determines that there is backlight in the captured image of the previous frame, and therefore changes the backlight determination threshold value R0 to 70%. Therefore, the backlight state determination unit 280 determines that the backlight state is in the backlight state because the backlight intensity R exceeds the backlight determination threshold value R0.

  Next, when the frame number is “5”, the backlight intensity R exceeds 70% but is less than 80%. At this time, the backlight state determination unit 280 determines that there is backlight in the captured image one frame before, and therefore does not change the backlight determination threshold value R0 from 70%. Therefore, the backlight state determination unit 280 determines that the backlight state is in the backlight state because the backlight intensity R exceeds the backlight determination threshold value R0.

  Next, when the frame number is “6”, the backlight intensity R is less than 70%. At this time, the backlight state determination unit 280 determines that there is backlight in the captured image one frame before, and therefore does not change the backlight determination threshold value R0 from 70%. Therefore, the backlight state determination unit 280 determines that the backlight state is not the backlight state because the backlight intensity R does not exceed the backlight determination threshold value R0.

  Next, when the frame number is “7”, the backlight intensity R is over 70% but less than 80%. At that time, the backlight state determination unit 280 determines that there is no backlight in the captured image one frame before, and thus returns the backlight determination threshold value R0 from 70% to 80%. Therefore, the backlight state determination unit 280 determines that the backlight state is not the backlight state because the backlight intensity R does not exceed the backlight determination threshold value R0.

  Next, when the frame number is “8”, the backlight intensity R exceeds 80%. At that time, since the backlight state determination unit 280 determines that there is no backlight in the captured image of the previous frame, the backlight determination threshold value R0 is not changed from 80%. Therefore, the backlight state determination unit 280 determines that the backlight state is in the backlight state because the backlight intensity R exceeds the backlight determination threshold value R0.

  FIG. 8 is a flowchart illustrating an example of a processing procedure of the imaging apparatus 100 according to the embodiment of the present invention.

  First, the image acquisition unit 210 acquires a captured image captured by the image sensor 120 via the digital signal processing unit 140 (step S911).

  Next, the exposure amount acquisition unit 250 acquires the exposure amount from information such as the aperture value and shutter speed of the imaging device 100 (step S912).

  Next, the backlight intensity J1 is calculated based on the captured image acquired in step 911 (step S930).

  Next, the correction factor calculation unit 260 calculates the correction factor J2 based on the exposure amount acquired in step S912 (step S913).

  Next, the backlight intensity correction unit 270 calculates a corrected backlight intensity R0 that is a corrected value of the backlight intensity J1 based on the backlight intensity J1 calculated in step S930 and the correction factor J2 calculated in step 913. (Step S914).

  Next, the backlight state determination unit 280 determines whether or not the captured image of the previous frame is in the backlight state (step S915). At this time, if the captured image one frame before is in the backlight state, the backlight determination threshold value R0 is set to 70% (step S916). On the other hand, when the captured image one frame before is not in the backlight state, the backlight determination threshold value R0 is set to 80% (step S917).

  Subsequently, the backlight state determination unit 280 compares the corrected backlight intensity R calculated in step S914 and the backlight determination threshold value R0 to determine whether or not the captured image acquired in step 911 is in the backlight state (step). S918). At this time, if the captured image is in a backlight state, the system control unit 180 controls each unit to convert the captured image so that the captured state becomes an appropriate state (step S919).

  FIG. 9 is a flowchart showing an example of a processing procedure for calculating the backlight intensity J1 in the embodiment of the present invention.

  First, one is selected from three arrangements (image directions) (step S931). In the embodiment of the present invention, three arrangements of the horizontal direction and the vertical direction of right rotation or left rotation are assumed.

  Next, based on the arrangement selected in step S931, the high luminance region 330 and the low luminance region 340 are separated from the captured image acquired in step S911 in FIG. 8 (step S932).

  Next, one of the candidates for the position of the backlight pattern 350 is selected (step S931). In the embodiment of the present invention, as shown in FIGS. 4B to 4F, the positions of five backlight patterns 350 are assumed.

  Next, the backlight region extraction unit 220 calculates an average luminance value in the backlight region 360 corresponding to the backlight pattern 350 selected in step S931 (step S934).

  Next, it is determined whether or not the average luminance value of the backlight region 360 candidate has been calculated for all the positions of the backlight pattern 350 (step S935). At this time, if the average luminance value of the backlight region 360 candidate has not been calculated for all positions of the backlight pattern 350, the process proceeds to step S933, and the above-described operation is repeated (steps S933 to S935). On the other hand, when the average luminance value is calculated for all the positions of the backlight patterns 350, the one having the lowest average luminance value among the positions of the five backlight patterns 350 is selected as the backlight region 360 (step S936). .

  Subsequently, the average luminance value of the high luminance region 330 separated in step S932 is calculated (step S937).

  Next, the light amount ratio X is calculated from the average luminance value of the backlight region 360 selected in step S936 and the average luminance value of the high luminance region 330 calculated in step S932 (step S938).

  Next, the backlight intensity J1 is calculated from the light amount ratio X calculated in step S938 (step S939).

  Then, it is determined whether or not all arrangements have been selected (step S941). At this time, if all the arrangements are not selected, the process proceeds to step S931, and the above-described operation is repeated (steps S931 to S941). On the other hand, when all the imaging directions are selected, the arrangement with the highest backlight intensity J1 calculated in step S939 and the backlight intensity J1 are adopted (step S942).

  As described above, according to the embodiment of the present invention, the number of the backlight patterns 350 for extracting the backlight region 360 from the low luminance region 340 can be limited to a small number.

  In the embodiment of the present invention, the imaging direction is estimated by calculating the backlight intensity for the three arrangements (image directions). However, the processing is omitted when the imaging apparatus 100 has the imaging direction detection function. May be.

  Further, the present invention may be used in combination with other backlight discrimination methods. In that case, it is effective to set the backlight determination threshold value R0 in the embodiment of the present invention lower than the above setting example.

  The embodiment of the present invention is an example for embodying the present invention and has a corresponding relationship with the invention-specific matters in the claims as shown below, but is not limited thereto. However, various modifications can be made without departing from the scope of the present invention.

  That is, in claim 1, the image acquisition unit corresponds to, for example, the image acquisition unit 210. Further, the backlight region extraction unit corresponds to the backlight region extraction unit 220, for example. The light amount ratio calculating unit corresponds to, for example, the light amount ratio calculating unit 230. The backlight intensity calculation unit corresponds to the backlight intensity calculator 240, for example. Further, the backlight state determination unit corresponds to the backlight state determination unit 280, for example.

  Further, in claim 4, the backlight determination holding unit corresponds to, for example, the backlight determination holding unit 290.

  Further, in claim 6, the exposure amount acquisition unit corresponds to, for example, the exposure amount acquisition unit 250. Further, the correction factor calculation means corresponds to the correction factor calculator 260, for example. The backlight intensity correction unit corresponds to the backlight intensity correction unit 270, for example.

  Further, in claim 7, the imaging means corresponds to the imaging device 120, for example. The image acquisition unit corresponds to the image acquisition unit 210, for example. Further, the backlight region extraction unit corresponds to the backlight region extraction unit 220, for example. The light amount ratio calculating unit corresponds to, for example, the light amount ratio calculating unit 230. The backlight intensity calculation unit corresponds to the backlight intensity calculator 240, for example. Further, the backlight state determination unit corresponds to the backlight state determination unit 280, for example.

  In claim 8 or 9, the image acquisition procedure corresponds to, for example, step S911. The backlight region extraction procedure corresponds to, for example, step S936. The light amount ratio calculation procedure corresponds to, for example, step S938. The backlight intensity calculation procedure corresponds to, for example, step S939. The backlight state determination procedure corresponds to, for example, step S918.

  The processing procedure described in the embodiment of the present invention may be regarded as a method having a series of these procedures, and a program for causing a computer to execute these series of procedures or a recording medium storing the program May be taken as

It is a block diagram which shows the function structural example of the imaging device 100 in embodiment of this invention. It is a block diagram which shows the function structural example of the backlight determination by the system control part 180 in embodiment of this invention. It is a figure which shows the example in which the captured image in embodiment of this invention is isolate | separated into the high-intensity area | region 330 and the low-intensity area | region 340. FIG. It is the figure which showed the procedure which extracts the backlight area | region from the low-intensity area | region 340 by the backlight area extraction part 220 in embodiment of this invention. It is the figure shown about the detection method of the imaging direction by the backlight intensity calculation part 240 in embodiment of this invention. It is the figure which showed an example of the calculation method of the correction factor J2 by the correction factor calculation part 260 in embodiment of this invention. It is the figure shown about the change of the threshold value used for the backlight state determination by the backlight state determination part 280 in embodiment of this invention. It is a flowchart which shows the example of a process sequence of the imaging device 100 in embodiment of this invention. It is a flowchart which shows the example of a process sequence of calculation of the backlight intensity J1 in embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Imaging device 110 Lens part 120 Imaging element 130 Analog signal processing part 140 Digital signal processing part 150 Display part 160 Lens control part 170 Timing generator 180 System control part 190 Strobe 200 Imaging operation reception part 210 Image acquisition part 220 Backlight area extraction part 230 Light intensity ratio calculation unit 240 Backlight intensity calculation unit 250 Exposure amount acquisition unit 260 Correction rate calculation unit 270 Backlight intensity correction unit 280 Backlight state determination unit 290 Backlight determination holding unit 300 Imaging region 310 Subject 320 Block 330 High luminance region 340 Low luminance region 350 Backlight pattern 360 Backlight area

Claims (9)

Image acquisition means for acquiring a captured image and separating the captured image into at least two regions of a high luminance region and a low luminance region;
A backlight region extraction means for searching for a region where the average value of the luminance value is the lowest with respect to a predetermined backlight pattern in the low luminance region and extracting it as a backlight region;
A light amount ratio calculating means for calculating, as a light amount ratio, a ratio between an average value of luminance values in the high luminance region and an average value of luminance values in the backlight region;
A backlight intensity calculating means for calculating a backlight intensity based on the light amount ratio;
A backlight discrimination device, comprising: a backlight state determination unit that determines that the backlight is in a backlight state when the backlight intensity exceeds a predetermined threshold value.   2. The backlight discrimination device according to claim 1, wherein the backlight intensity calculation unit calculates the backlight intensity as an after event of the light amount ratio.   2. The backlight discrimination according to claim 1, wherein the image acquisition unit sets a predetermined area above the captured image as the high luminance area and a predetermined area below the captured image as the low luminance area. apparatus. Further comprising backlight determination holding means for storing a determination result as to whether or not the backlight state is the result of the determination in the backlight state determination means;
2. The backlight discrimination device according to claim 1, wherein the backlight state determination unit changes the predetermined threshold to a lower value when the determination result is the backlight state. 3. The image acquisition means includes: a first arrangement in which a predetermined area at the top of the captured image is the high luminance area and a predetermined area at the bottom of the captured image is the low luminance area; and a left area of the captured image A second arrangement in which a predetermined area is the high luminance area and a predetermined area on the right side of the captured image is the low luminance area, and a predetermined area on the right side of the captured image is the high luminance area and the imaging is performed. Separating a predetermined area on the left side of the image into at least two areas for at least three arrangements with the third arrangement as the low luminance area,
2. The backlight according to claim 1, wherein the backlight intensity calculation unit determines the one having the highest backlight intensity calculated among the three arrangements as a correct arrangement and outputs the backlight intensity of the arrangement. Discriminator. Exposure amount acquisition means for acquiring an exposure amount when the captured image is captured;
A correction rate calculating means for calculating the degree of necessity for correcting the backlight intensity as a correction rate based on the exposure amount;
The backlight discrimination device according to claim 1, further comprising a backlight intensity correction unit that corrects the backlight intensity based on the correction factor. Imaging means for imaging a subject and generating a captured image;
Image acquisition means for acquiring the captured image and separating it into at least two regions of a high luminance region and a low luminance region;
A backlight region extraction means for searching for a region where the average value of the luminance value is the lowest with respect to a predetermined backlight pattern in the low luminance region and extracting it as a backlight region;
A light amount ratio calculating means for calculating, as a light amount ratio, a ratio of an average value of luminance values in the high luminance region and an average value of luminance values in the backlight region;
A backlight intensity calculating means for calculating a backlight intensity based on the light amount ratio;
An imaging apparatus comprising: a backlight state determination unit that determines that the backlight is in a backlight state when the backlight intensity exceeds a predetermined threshold value. A backlight discrimination method in an imaging apparatus that images a subject and generates a captured image,
An image acquisition procedure for acquiring the captured image and separating the captured image into at least two regions of a high luminance region and a low luminance region;
A backlight region extraction procedure for searching for a region where the average value of the luminance value is the lowest for a predetermined backlight pattern in the low luminance region and extracting it as a backlight region;
A light amount ratio calculation procedure for calculating a ratio of an average value of luminance values in the high luminance region and an average value of luminance values in the backlight region as a light amount ratio;
A backlight intensity calculation procedure for calculating the backlight intensity based on the light amount ratio;
A backlight discrimination method comprising: a backlight state determination procedure for determining that the backlight is in a backlight state when the backlight intensity exceeds a predetermined threshold value. In an imaging device that images a subject and generates a captured image,
An image acquisition procedure for acquiring the captured image and separating the captured image into at least two regions of a high luminance region and a low luminance region;
A backlight region extraction procedure for searching for a region where the average value of the luminance value is the lowest for a predetermined backlight pattern in the low luminance region and extracting it as a backlight region;
A light amount ratio calculation procedure for calculating a ratio of an average value of luminance values in the high luminance region and an average value of luminance values in the backlight region as a light amount ratio;
A backlight intensity calculation procedure for calculating the backlight intensity based on the light amount ratio;
A program that causes a computer to execute a backlight state determination procedure for determining that the backlight is in a backlight state when the backlight intensity exceeds a predetermined threshold.

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