JP2012165222A - Light irradiation state determination device, light irradiation state determination method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light irradiation state determination device which can ensure stabilized determination results.SOLUTION: A light irradiation state determination device comprises a comparison determination unit which determines whether or not an image being determined is in a predetermined light irradiation state according to a predetermined criterion, and a determination result storage unit which stores the determination results of a previous image being determined. When a determination is made that the previous image being determined is in the predetermined light irradiation state, the comparison determination unit determines the image being determined by using a second criterion with which a determination is made easily that the image being determined is in the predetermined light irradiation state when compared with a first criterion used when a determination is made that the previous image being determined is not in the predetermined light irradiation state.

Description

  The present invention relates to a light irradiation state determination device that determines a light irradiation state such as backlight, and more particularly to a light irradiation state determination device that can obtain a stable determination result.

  Conventionally, a display unit that can display a subject image obtained from an image sensor such as a CCD (Charge Coupled Devise) in real time, or reproduce and display a subject image recorded on a recording medium such as a memory card, a magnetic tape, or a magnetic disk. Imaging devices such as digital still cameras and movie cameras provided are known. In particular, at the time of imaging, the photographer checks the photographing conditions such as composition and appropriateness of exposure by looking at the subject image displayed on the display unit.

  In general, in such an imaging device, exposure correction, gradation correction such as gamma and knee are often performed automatically, but in addition, there is a phenomenon that the subject due to high contrast conditions such as overexposure, overexposure, backlighting, etc. There are many imaging devices that can automatically determine and correct a phenomenon in which a subject is too bright due to a high contrast state, such as a dark spot and a spotlight only on the subject. Further, as a determination material for intentionally correcting by a user, there is a method for determining a light irradiation state such as backlight and displaying a determination result.

  When images such as moving images are continuously captured using such an imaging device, the corrected image and the determination result frequently change due to a subtle change in the position of the subject or a change in the light source. The judgment result may not be stable.

  With regard to this problem, Patent Document 1 discloses a stable moving image by detecting a luminance histogram from a moving image, providing a limit width when changing the gradation correction characteristics based on the result, and dynamically changing the limit width. Is described.

JP 2008-17321 A

  However, in the method of providing a limit range for gradation correction corresponding to the light irradiation state, a stable moving image can be obtained by automatic correction, but a determination result of the stable light irradiation state cannot be obtained. Due to a subtle change in the position of the main subject or a change in illumination light, the determination result of backlight or the like is frequently switched.

  For this reason, when the user wants to intentionally perform exposure and gradation correction corresponding to the light irradiation state, it is impossible to provide a stable determination result of the light irradiation state. In addition, when the light irradiation state is first determined and control is performed to operate automatic exposure correction or automatic gradation correction corresponding to backlight if it is determined to be backlight, stable correction operation cannot be performed. It was.

  Then, an object of this invention is to provide the light irradiation state determination apparatus which can obtain the stable determination result.

  In order to solve the above problem, the light irradiation state determination device according to the first aspect of the present invention determines whether the determination target image is in a predetermined light irradiation state based on a histogram of the determination target image. A comparison determination unit that determines according to the determination criterion; and a determination result storage unit that stores a determination result of the immediately preceding determination target image, wherein the comparison determination unit is in a predetermined light irradiation state. Is determined using the second determination criterion that is more easily determined as the predetermined light irradiation state than the first determination criterion used when it is determined that the immediately preceding determination target image is not in the predetermined light irradiation state. An image is determined.

  Here, the determination criterion is to calculate the number of pixels having a luminance level including a number of pixels equal to or greater than a predetermined threshold among luminance levels within a predetermined range determined by the average luminance level in the histogram of the determination target image. The second determination criterion may be one in which the predetermined threshold is set smaller than the first determination criterion.

  Alternatively, the determination criterion defines an upper limit and a lower limit for each luminance level of the histogram, and the second determination criterion increases the upper limit with respect to the first determination criterion and decreases the lower limit. You may make it use a thing.

  Here, the second determination criterion may be such that the upper limit is uniformly increased at a predetermined rate with respect to the first determination criterion, and the lower limit is uniformly decreased at a predetermined rate.

  Alternatively, the second determination criterion is that the upper limit of the first determination criterion is increased and the lower limit is decreased in accordance with an enlargement range corresponding to the classification based on the shape of the first determination criterion. Also good.

  Alternatively, the second determination criterion may be determined in advance so as to increase the upper limit of the first determination criterion and decrease the lower limit.

  In order to solve the above-described problem, the light irradiation state determination method according to the second aspect of the present invention determines whether the determination target image is in a predetermined light irradiation state based on a histogram of the determination target image. In the light irradiation state determination method for determining according to the determination criterion, when it is determined that the immediately preceding determination target image is in the predetermined light irradiation state, it is determined that the immediately preceding determination target image is not in the predetermined light irradiation state. In this case, the determination target image is determined using a second determination criterion that is more easily determined as a predetermined light irradiation state than the first determination criterion used in this case.

  ADVANTAGE OF THE INVENTION According to this invention, the light irradiation state determination apparatus which can obtain the stable determination result is provided.

It is a block diagram which shows the structure of the imaging device which is one Embodiment of the light irradiation state determination apparatus of this invention. It is a block diagram which shows the structure of a light irradiation state determination part. It is a flowchart explaining the 1st Example of operation | movement of a light irradiation state determination part. It is a figure explaining calculation of the feature-value of the determination target image by 1st determination reference data and 2nd determination reference data, and determination of a light irradiation state. It is a figure explaining another example of calculation of the feature-value of a judgment object picture. It is a figure explaining a histogram pattern. It is a figure which shows the several histogram pattern corresponding to backlight. It is a flowchart explaining the 2nd Example of operation | movement of a light irradiation state determination part. It is a figure explaining the 1st criteria data and the 2nd criteria data of the 2nd example. It is a figure explaining the classification | category of a histogram pattern, and the expansion width. It is a figure explaining the 2nd criteria of the 4th example.

  Embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram illustrating a configuration of an imaging apparatus which is an embodiment of a light irradiation state determination apparatus of the present invention. The imaging apparatus according to the present embodiment determines the light irradiation state of the subject for the continuous images constituting the video. The light irradiation state to be determined can be, for example, a backlight state, but may be another state. The light irradiation state is determined for each field or several fields, and an image that is a determination target is referred to as a determination target image.

  The imaging apparatus can alert the user by performing image processing based on the determination result or displaying the determination result. In the imaging apparatus according to the present embodiment, a process for preventing the determination result from frequently switching due to a subtle change in the light irradiation state of the subject is performed.

  As shown in the figure, an imaging apparatus 100 includes a lens 11 that collects incident light from a subject, an exposure mechanism 12 having a diaphragm, an imaging element 13 such as a CCD / CMOS, and a CDS (correlated double sampling) circuit 14. AGC (automatic gain control) circuit 15, AD converter (ADC) 16, digital signal processing (DSP) circuit 17, dynamic random access memory (DRAM) 19, JPEG (Joint Photographic Experts Group) encoder 20, media I / F (interface) 21, static random access memory (SRAM) 22, flash memory (read-only memory) 23, NTSC / PAL encoder 24, DA converter (DAC) 25, central processing unit (CPU) ) 26, an exposure control unit 27, and an operation unit 28.

  The DSP circuit 17 includes a gradation correction unit 18 that performs predetermined signal processing and performs gradation correction therein. The CPU 26 is connected to the DSP circuit 17, JPEG encoder 20, media I / F 21, SRAM 22, and flash ROM 23 via the bus 29. The CPU 26 also includes a histogram calculation unit 31, a light irradiation state determination unit 32, a gradation correction value calculation unit 33, and an exposure correction value calculation unit 34.

  The exposure control unit 27 controls operations of the exposure mechanism 12, the image sensor 13, and the AGC circuit 15. The operation unit 28 receives an operation from the user and causes the CPU 26 to perform an operation based on the operation. The imaging device 100 is connected to a recording medium 35 such as a memory card and a display device 36 such as a television / liquid crystal display. The display device 36 may be built in the imaging device 100.

  In FIG. 1, incident light from a subject that has passed through a lens 11 and an exposure mechanism 12 and formed an image on a light receiving surface of an image sensor 13 is photoelectrically converted by the image sensor 13 into an image signal that is an electrical signal. The image signal is denoised by the CDS circuit 14 based on a known correlated double sampling method, the signal level is subsequently amplified by the AGC circuit 15, and further converted to a digital signal by the ADC 16.

  The digital image pickup signal output from the ADC 16 is subjected to gradation correction by a gradation correction unit 18 in the DSP circuit 17. The gradation-corrected digital imaging signal is converted into a luminance signal Y, a color signal Cb, and a color signal Cr (hereinafter collectively referred to as “YCbCr signal”) in the DSP circuit 17 and then known by the JPEG encoder 20. It is compressed with the JPEG method. The JPEG-compressed image file output from the JPEG encoder 20 is stored in the flash ROM 23 and simultaneously recorded on the recording medium 35 through the media I / F 21 and simultaneously stored in the SRAM 22.

  The YCbCr signal obtained by the signal processing in the DSP circuit 17 using the DRAM 19 is converted into an NTSC color video signal or a PAL color video signal by the NTSC / PAL encoder 24, and then in the DAC 25. After being converted into an analog color video signal, it is supplied to the display device 36 and displayed as a color image.

  On the other hand, the CPU 26 on the bus 29 creates a histogram for each field or several fields from the Y signal stored in the SRAM 22 by the histogram calculation unit 31. This histogram represents the distribution state of the luminance level of the determination target image, and is a graph showing the number of pixels for each luminance level of the image in each field or several field periods. For example, if the luminance signal is 8 bits, the luminance level is represented by 256 levels, but in this embodiment, 256 levels are grouped into, for example, 16 levels or 5 levels, and 16 or 5 luminance level ranges. Create a histogram showing how many pixels there are for each.

  The light irradiation state determination unit 32 determines the light irradiation state of the determination target image based on the created histogram. The light irradiation state to be determined is a back light state in the present embodiment, but is not limited to the back light state. For example, a high contrast state in which the surrounding is dark and a part of the light is spotted may be determined. .

  The gradation correction value calculation unit 33 calculates gradation correction values such as gamma and knee, and drives and controls the gradation correction unit 18. The exposure correction value calculation unit 34 calculates an exposure correction value and controls the exposure control unit 27. The gradation correction value calculation unit 33 and the exposure correction value calculation unit 34 can change the control content according to the determination result of the light irradiation state determination unit 32. For example, when the light irradiation state determination unit 32 determines that the light irradiation state of the subject is backlit, the gradation correction value and the exposure correction value are calculated so that the main subject person does not become dark. Also, if it is determined that the surroundings are dark and a high contrast state such as a part of which is spotlighted, gradation correction values and exposure correction values are calculated so that the main subject person does not become too bright.

  The exposure control unit 27 linearly adjusts the aperture value of the exposure mechanism 12 and adjusts the shutter speed of the image sensor 13 with a time constant based on the exposure correction value obtained by the exposure correction value calculation unit 34. Then, the exposure is adjusted to an appropriate value by adjusting the gain of the AGC circuit 15.

  As shown in FIG. 2, the light irradiation state determination unit 32 includes a determination comparison unit 321, determination reference data 322, and a determination result storage unit 323. The determination result storage unit 323 stores a determination result for the immediately previous determination target image.

  The determination comparison unit 321 determines the light irradiation state of the determination target image based on the histogram calculated by the histogram calculation unit 31. Specifically, in this embodiment, it is determined whether it is backlight. At this time, the determination comparison unit 321 refers to the determination reference data 322 and the determination result storage unit 323.

When it is determined that the immediately preceding determination target image is backlit, the determination comparison unit 321 makes it easier to determine that the determination target image is backlit than when the immediately preceding determination target image is determined not to be backlit. Is used to determine whether the determination target image is backlit. Thereby, once it is determined that the light is backlit, it is easily determined that the light is continuously backlit, so that a stable determination result that does not frequently switch can be obtained.
<First embodiment>

  Specific operations of the light irradiation state determination unit 32 will be described in detail with reference to the first to fourth embodiments. FIG. 3 is a flowchart for explaining the first embodiment of the operation of the light irradiation state determination unit 32.

  First, the determination comparison unit 321 of the light irradiation state determination unit 32 inputs the histogram of the determination target image from the histogram calculation unit 31 (S101). In the first embodiment, the histogram calculation unit 31 calculates a 16-level histogram.

  Next, the determination comparison unit 321 refers to the determination result storage unit 323 to determine whether the determination result of the immediately previous determination target image is “true”, that is, whether it is determined to be backlight (S102). As a result, when it is determined that the determination result of the immediately preceding determination target image is “false”, that is, not backlight (S103: No), the feature amount of the determination target image is calculated using the first determination reference data (S104), When it is determined that the determination result of the immediately preceding determination target image is “true”, that is, backlight (S103: Yes), the characteristics of the determination target image are calculated using the second determination reference data (S105). The light irradiation state is determined based on the feature amount (S106).

  Here, the first determination reference data and the second determination reference data are determination reference rules included in the determination reference data 322, and the second determination reference data is a determination reference that is more easily determined as backlight than the first determination reference data. It is a rule.

  Calculation of the feature amount of the determination target image based on the first determination reference data and determination of the light irradiation state will be described with reference to FIG. FIG. 4A shows a 16-stage histogram of the comparison target image. The determination comparison unit 321 calculates an average luminance level based on the histogram, and sets a level shifted from the average luminance level (Ave) to the high luminance level side by a predetermined level as the threshold value # 1. In the example of this figure, it is assumed that the luminance level four levels above the average luminance level (Ave) is set as the threshold value # 1.

  Then, the number of pixels having a luminance level having a number of pixels equal to or greater than a predetermined threshold # 2 is counted in a luminance level range equal to or greater than the threshold # 1. In the example of this figure, the number of pixels in the wavy rectangle corresponds. At this time, the count value of the number of pixels may be weighted. For example, the weight can be set to a value such that the weight increases as the brightness level increases.

  If the count value or the value obtained by weighting the count value is equal to or greater than the predetermined threshold # 3, it is determined that the backlight is in the backlight state. As the threshold value # 1, the threshold value # 2, and the threshold value # 3, for example, appropriate values can be determined experimentally.

  In calculating the feature amount of the determination target image based on the second determination reference data and determining the light irradiation state, at least one of the threshold # 1, threshold # 2, and threshold # 3 is made different from the first determination reference data. Thus, the backlight is more easily determined than the first determination reference data. For example, as shown in FIG. 4B, the threshold value # 2 is set to a value smaller than the threshold value # 2 (dotted line A in the figure) of the first determination reference data, and the number of pixels to be counted (the waveform rectangle in the figure) The number of pixels) can be increased. Alternatively, the threshold value # 1 or the threshold value # 3 may be set to a value smaller than the first determination reference data so that the count value or the value obtained by weighting the count value is likely to be equal to or greater than the predetermined threshold value # 3. How much the threshold value in the second determination reference data is reduced can be determined using, for example, statistics of the histogram of the sample image that can be regarded as backlight.

  As a result, when it is determined that the determination target image is backlight, the gradation correction value calculation unit 33 and the exposure correction value calculation unit 34 are caused to calculate a correction value for correcting the backlight. In addition, it is desirable to display the display device 36 to indicate that it is backlit and to alert the user. At this time, once it is determined that the light is backlit, it is easily determined that the light is backlit continuously. Therefore, the display indicating that it is backlit does not fluctuate in an unstable manner and is displayed stably.

  Returning to the description of the flowchart of FIG. 3, when the light irradiation state is determined, the determination result is stored in the determination result storage unit 323 (S107). This evaluation result is used for evaluation of the next evaluation target image. The above processing is repeated until the input of the histogram is completed (S108).

  For determining the light irradiation state, when determining a high contrast state in which the surrounding is dark and a part of the light is spotlighted, for example, determination reference data as shown in FIG. 5 can be used. That is, a level shifted from the average luminance level (Ave) by a predetermined level toward the low luminance level is set as the threshold value # 4. Then, in the luminance level range below the threshold value # 4, the number of pixels having the luminance level having the pixel number above the predetermined threshold value # 5 is counted. At this time, the count value of the number of pixels may be weighted. For example, the weight can be set to a value such that the weight increases as the luminance level decreases.

  If the count value or the value obtained by weighting the count value is equal to or greater than the predetermined threshold value # 6, it is determined that the state is in a high contrast state. As the threshold value # 4, the threshold value # 5, and the threshold value # 6, for example, appropriate values can be determined experimentally.

Also in this case, in the calculation of the feature amount of the determination target image based on the second determination criterion data and the determination of the light irradiation state, at least one threshold among the threshold # 4, the threshold # 5, and the threshold # 6 is set as the first determination criterion. Different from the data, it is easier to determine a higher contrast state than the first determination reference data.
<Second embodiment>

  Next, a second embodiment of the operation of the light irradiation state determination unit 32 will be described. In the second embodiment, a histogram pattern as shown in FIG. 6A is used as the determination reference data 322 used for determining the light irradiation state. As shown in the figure, the histogram pattern divides the histogram into five levels of low luminance, medium low luminance, medium luminance, medium high luminance, and high luminance, and defines an upper limit and a lower limit for each.

  As shown in FIG. 6B, if the determination target image is within the upper and lower limits of the histogram pattern at all luminance levels, the determination target image matches the histogram pattern. Then, if the five-stage histogram of the image to be judged does not fall between the upper and lower limits of the histogram pattern at any luminance stage as shown in FIG. It is determined that they do not match.

  For example, as shown in FIG. 7, a plurality of histogram patterns are prepared corresponding to backlight and stored as determination reference data 322. If any of the histogram patterns corresponding to backlight is matched, the determination target image is determined to be backlight. On the other hand, if it does not match all the histograms corresponding to backlight, the determination target image is determined. It is determined that the image is not backlit. The histogram pattern can be statistically created using a large number of sample images.

  FIG. 8 is a flowchart for explaining a second embodiment of the operation of the light irradiation state determination unit 32. First, the determination comparison unit 321 of the light irradiation state determination unit 32 inputs the histogram of the determination target image from the histogram calculation unit 31 (S201). In the second embodiment, the histogram calculation unit 31 calculates a five-stage histogram.

  Then, a histogram pattern used for determination is set (S202). Here, one of the histogram patterns corresponding to the backlight stored as the determination reference data 322 is set. In the second example, the determination result storage unit 323 records for each set histogram pattern.

  Next, the determination comparison unit 321 refers to the determination result storage unit 323 to determine whether or not the determination result of the immediately previous determination target image based on the set histogram pattern is “true”, that is, matches the histogram pattern (see FIG. S203).

  As a result, when it is determined that the determination result of the immediately preceding determination target image is “false”, that is, does not match the histogram pattern (S204: No), the first determination reference data is used (S205). If the determination result of the target image is “true”, that is, it is determined that it matches the histogram pattern (S204: Yes), the determination target image matches the histogram pattern using the second determination reference data (S206). Whether or not (S207).

  Here, as the first determination reference data, as shown in FIG. 9A, the histogram pattern set in the process (S202) is used as it is. Further, as shown in FIG. 9B, the second determination reference data is a histogram pattern in which the upper and lower limits of the histogram pattern set in the process (S202) are uniformly expanded. For this reason, it becomes easier to determine that the second determination reference data match. In this figure, the degree of enlargement is 2% for both the upper limit and the lower limit. However, the degree of enlargement is not limited to this value. For example, an appropriate value may be obtained experimentally.

  When the match determination with the histogram pattern is performed using the first determination reference data or the second determination reference data, the determination result is stored in the determination result storage unit 323. As described above, the determination result is stored for each histogram pattern. For this reason, even if it is determined that a certain histogram pattern matches, determination is performed for all histogram patterns.

  When a match is determined using a certain histogram pattern (S207) and the determination result is recorded (S208), the determination is performed similarly using another histogram pattern, and the determination is repeated for all histogram patterns (S209). For any histogram pattern, if the determination result immediately before the histogram pattern is “true”, the determination is performed using the second determination reference data in which the upper and lower limits of the histogram pattern are uniformly expanded, and the immediately preceding determination is performed. If the result is “false”, the determination is performed using the first determination reference data of the histogram pattern as it is.

  As a result of the match determination for all the histogram patterns, if any of the histogram patterns is determined to be “true”, the light irradiation state is determined to be backlight and “false” is determined for all histogram patterns. If it is determined that the light irradiation state is not backlight (S210). The above processing is repeated until the input of the histogram is completed (S211).

Also in the second embodiment, when it is determined that the determination target image is backlight, the gradation correction value calculation unit 33 and the exposure correction value calculation unit 34 are caused to calculate a correction value for correcting the backlight. In addition, it is desirable to display the display device 36 to indicate that it is backlit and to alert the user.
<Third embodiment>

  Next, a third example of the operation of the light irradiation state determination unit 32 will be described. In the second embodiment described above, if the determination result immediately before a certain histogram pattern is “true”, the determination is performed using the second determination reference data in which the upper and lower limits of the histogram pattern are uniformly expanded. However, in the third embodiment, the histogram pattern is classified according to its shape, and the upper and lower enlargement widths are changed according to the classification. Specifically, the histogram pattern that is more likely to be backlit is changed so that the enlargement width is increased. Thus, if the immediately preceding determination target image matches a histogram pattern that is highly likely to be backlit, the next determination target image is more easily determined to be backlit. Other processes in the third embodiment are the same as those in the second embodiment.

  FIG. 10A is a diagram for explaining the classification of the histogram pattern. The item “pattern” in this figure represents the shape of the histogram pattern as a sequence of five numerical values. Each numerical value is in the order of low luminance, medium low luminance, medium luminance, medium high luminance, and high luminance. The ranking of the number of pixels is shown. Here, 1 is the smallest and 5 is the largest.

  For example, the histogram pattern classified as “54321” has a shape in which the low luminance is the highest at 5, the high luminance is the lowest at 1, and monotonously decreases from the low luminance to the high luminance. The histogram pattern shown in FIG. 6A is classified as “51234” because medium luminance <medium luminance <medium high luminance <high luminance <low luminance.

  The item “number of samples” in FIG. 10A is the number of sample images classified into each “pattern” among the histograms of a large number of sample images. The item “number of backlights” is the number of sample images recognized as backlight among the sample images classified into the respective “patterns”. Then, the item “backlight rate” is calculated based on “number of samples” and “backlight number”. By creating such a table, it is possible to acquire a high or low tendency of the possibility of backlighting for each classification of the histogram pattern.

  For the histogram pattern classified as a pattern with a high backlight rate, the enlargement width is increased. The enlargement width of the enlargement ratio can be set according to a table as shown in FIG. In the example of this figure, the enlargement width is determined for each range of the backlight ratio, and the enlargement width is set to be larger as the backlight ratio is higher.

For example, the histogram pattern classified into the pattern “54321” has a backlight rate of 5.6%, and therefore the upper and lower limits are each enlarged by 1.0% in the second determination reference data. Further, the histogram pattern classified as the pattern “53124” has a backlight rate of 32.0%, and therefore, the upper limit and the lower limit are each enlarged by 3.0% in the second determination reference data.
<Fourth embodiment>

  Next, a fourth embodiment of the operation of the light irradiation state determination unit 32 will be described. In the second embodiment described above, if the determination result immediately before a certain histogram pattern is “true”, the determination is performed using the second determination reference data in which the upper and lower limits of the histogram pattern are uniformly expanded. However, in the fourth embodiment, a histogram pattern for the second determination reference data is prepared in advance for each histogram pattern.

For example, as shown in FIG. 11, for each of pattern 1, pattern 2,..., A histogram pattern used as first determination reference data and a histogram pattern used as second determination reference data are prepared. Also in this case, the second determination reference data is a histogram pattern that is more easily determined as backlight than the first determination reference data, that is, a histogram pattern in which the upper limit and the lower limit are expanded as compared with the first determination reference data. Note that the first determination reference data and the second determination reference data need not have the same shape.
<Others>

  In the second and third embodiments described above, the upper limit and the lower limit are enlarged at the same ratio for each luminance stage, but the enlargement width is made different for each luminance stage. May be. Also in this case, the optimum enlargement width for each luminance stage can be obtained experimentally using a large number of sample images. The above-described embodiments can be combined or selectively used.

  As described above, in the present embodiment, when the immediately preceding determination target image is determined to be backlit, a criterion that makes it easier to determine backlit is used than when the immediately preceding determination target image is determined not to be backlit. Therefore, once the backlight is determined, the backlight is easily determined continuously. Accordingly, it is possible to prevent the backlight determination result from being frequently switched due to a subtle change in the light irradiation state of the subject.

DESCRIPTION OF SYMBOLS 11 ... Lens, 12 ... Exposure mechanism, 13 ... Imaging device, 14 ... CDS circuit, 15 ... AGC circuit, 16 ... ADC, 17 ... DSP circuit, 18 ... Tone correction part, 19 ... DRAM, 20 ... JPEG encoder, 21 ... Media I / F, 22 ... SRAM, 23 ... Flash ROM, 24 ... Encoder, 25 ... DAC, 26 ... CPU, 27 ... Exposure control unit, 28 ... Operation unit, 29 ... Bus, 31 ... Histogram calculation unit, 32 ... Light irradiation state determination unit, 33 ... gradation correction value calculation unit, 34 ... exposure correction value calculation unit, 35 ... recording medium, 36 ... display device, 100 ... imaging device, 321 ... determination comparison unit, 322 ... determination reference data, 323 ... Determination result storage unit

Claims (7)

A comparison determination unit that determines whether the determination target image is in a predetermined light irradiation state based on a histogram of the determination target image according to a predetermined determination criterion;
A determination result storage unit that stores the determination result of the immediately preceding determination target image,
The comparison determination unit
When it is determined that the immediately preceding determination target image is in the predetermined light irradiation state, the predetermined light irradiation state is higher than the first determination criterion used when it is determined that the immediately preceding determination target image is not in the predetermined light irradiation state. A light irradiation state determination device, wherein the determination target image is determined using a second determination criterion that is easily determined.   The determination criterion is to calculate the number of pixels having a luminance level including a number of pixels equal to or greater than a predetermined threshold among luminance levels within a predetermined range determined by an average luminance level in the histogram of the determination target image. 2. The light irradiation state determination device according to claim 1, wherein the second determination criterion is such that the predetermined threshold is set smaller than the first determination criterion.   The determination criterion defines an upper limit and a lower limit for each luminance level of the histogram, and the second determination criterion is obtained by increasing the upper limit and decreasing the lower limit with respect to the first determination criterion. The light irradiation state determination apparatus according to claim 1, wherein the light irradiation state determination apparatus is provided.   4. The second determination criterion is characterized in that the upper limit is uniformly increased at a predetermined rate and the lower limit is uniformly decreased at a predetermined rate with respect to the first determination criterion. The light irradiation state determination apparatus of description.   The second determination criterion is such that the upper limit of the first determination criterion is increased and the lower limit is decreased in accordance with an enlargement range determined corresponding to the classification based on the shape of the first determination criterion. The light irradiation state determination apparatus according to claim 3.   The light irradiation state determination device according to claim 3, wherein the second determination criterion is determined in advance so as to increase the upper limit of the first determination criterion and decrease the lower limit. A light irradiation state determination method for determining, based on a histogram of a determination target image, whether the determination target image is in a predetermined light irradiation state according to a predetermined determination criterion,
When it is determined that the immediately preceding determination target image is in the predetermined light irradiation state, the predetermined light irradiation state is higher than the first determination criterion used when it is determined that the immediately preceding determination target image is not in the predetermined light irradiation state. A method of determining a light irradiation state, wherein the determination target image is determined using a second determination criterion that is easily determined.