JP2003087646A - Imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a backlight state with higher precision than before by applying this invention to an image pickup device to, for example, an electronic still camera. SOLUTION: The maximum value, mean value, and minimum value of luminance level are detected from an image pickup result, thresholds LH and LL are set according to them, and the luminance level DK is classified on the basis of those thresholds LH and LL to perform exposure control.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup device,
For example, it can be applied to an electronic still camera. The present invention detects a maximum value, an average value, and a minimum value of a brightness level from an image pickup result, sets a threshold value from these values, classifies the brightness level by the threshold value, and controls exposure. Therefore, it is possible to detect a backlit state with higher accuracy than the above.

[0002]

2. Description of the Related Art Conventionally, in an image pickup apparatus such as a video camera or an electronic still camera, an integral value, an average value, a weighted addition value, etc. according to a brightness level of an image pickup result are set as a judgment reference value, and the judgment reference value is set to a predetermined value. The automatic exposure control is performed by controlling the diaphragm or the like so that the value becomes.

In such an automatic exposure control method,
A method has been proposed in which the entire screen is brightened by detecting the state of backlight and the control amount is corrected, and the exposure of the subject at backlight is controlled with appropriate brightness (for example, Japanese Patent Laid-Open No. 2000-2000). -4393, JP-A-9-2
66549, JP-A-6-311423 and JP-A-6-189186).

In many of these methods, one screen is divided horizontally and vertically by a predetermined number of divisions to set a plurality of areas, the brightness level of each area is judged, and the judgment result is processed. Thus, the state of backlight is detected, or a determination reference value suitable for the state of backlight is obtained.

That is, in the method of detecting the backlit state by processing the determination result obtained in this way, a bright region having a predetermined threshold value or more and a predetermined threshold are determined from the determination result thus obtained. By determining the ratio of the brightness of the dark area equal to or less than the value, it is automatically determined whether or not the scene is a backlight scene.

On the other hand, in the method of dealing with the backlight by obtaining the judgment reference value suitable for the backlight condition, the target object is likely to be present in the center of the screen, and the screen is By generating the determination reference value with emphasis on the central region, it is possible to ensure appropriate brightness for the backlit subject.

[0007]

However, in such a method for dealing with backlight, there is still a problem in practical use.

That is, in the former method of detecting the backlight state by processing the determination result, there is a case where it is erroneously determined that the area other than the subject having a small brightness level is also imaged by the backlight, which causes In this case, it becomes difficult to control the exposure properly. In the latter method of obtaining a judgment reference value suitable for a backlight condition, for example, when a subject in a backlight condition does not exist in the center of the screen, exposure control is performed so that the background and the like have appropriate brightness. As a result, the original subject is imaged in a state in which the brightness is dark and crushed.

The present invention has been made in consideration of the above points, and it is an object of the present invention to propose an image pickup apparatus capable of detecting a backlit state with higher accuracy than ever before.

[0010]

In order to solve such a problem, in the invention of claim 1, level detecting means for detecting the maximum value, the minimum value and the average value of the brightness level of the imaging result,
Threshold setting means for setting a predetermined threshold value based on the maximum value, the minimum value, and the average value, and a classifying means for classifying the brightness level of the imaging result into a plurality of sections based on the threshold value. And area detecting means for detecting the area of the imaging result belonging to each section based on the classification of this classification means, and determination means for judging the detection result by the area detecting means and judging the backlight of the imaging result. Be prepared.

According to the structure of claim 1, the level detecting means for detecting the maximum value, the minimum value and the average value of the brightness level of the image pickup result, and the predetermined value based on the maximum value, the minimum value and the average value. A threshold setting means for setting a threshold value, a classifying means for classifying the brightness level of the imaging result into a plurality of sections based on the threshold value based on the threshold value, and a classifying means for the classifying means. Based on the above, the area detection means for detecting the area of the image pickup result belonging to each section, and the judgment means for judging the detection result by this area detection means and judging the backlight of the image pickup result are included. It is possible to appropriately set the threshold value according to the distribution of the brightness level, and check the brightness distribution with reference to this threshold value to determine whether the backlight is present or not. Thereby, for example, even when a light source or the like having an extremely high brightness level is imaged on the screen, it is possible to correctly determine whether or not there is backlight. As a result, it is possible to detect the backlit state with higher accuracy than before.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below in detail with reference to the drawings as appropriate.

(1) First Embodiment (1-1) Configuration of First Embodiment FIG. 1 is a block diagram showing an electronic still camera according to an embodiment of the present invention. In this electronic still camera 1, a CCD (Charge Coupled Device) 2 is a single-plate type solid-state image pickup device for color image, and operates by various drive signals output from a timing generator (TG) 3 to generate an optical system (not shown). The photoelectric conversion is performed on the image of the subject formed on the image pickup surface and the image pickup signal which is the image pickup result is output.

The timing generator 3 generates and outputs various drive signals for the CCD 2. In this process,
The timing generator 3, under the control of the automatic exposure controller 4, changes the timing of the drive signal so as to change the charge storage time of the CCD 2. As a result, in the electronic still camera 1, the shutter speed of the electronic shutter can be variously changed under the control of the automatic exposure control unit 4.

The AGC circuit 5 receives an image pickup signal output from the CCD 2 via a correlated double sampling circuit (not shown), amplifies the image pickup signal with a predetermined gain, and outputs the amplified image pickup signal. In this processing, the AGC circuit 5 changes the gain by the control signal output from the digital-analog conversion circuit (D / A) 6, and the digital-analog conversion circuit 6
Outputs the control signal by subjecting the control data output from the automatic exposure control unit 4 to digital-analog conversion processing.
As a result, the AGC circuit 5 and the digital-analog conversion circuit 6 are connected to the automatic exposure controller 4 and the DSP (Digital Signal pro
cessor) 7 together with the automatic exposure control process by AGC.

Analog-to-digital conversion circuit (A / D) 8
Outputs the output signal of the AGC circuit 5 after analog-digital conversion processing.

The DSP 7 performs knee processing, gamma correction processing, and the like on the output signal of the analog-digital conversion circuit 8, and compresses the image data DV obtained as a result, and outputs it. When the CCD 2 is an image sensor in which a color filter of a complementary color system is arranged, the DSP 7 performs arithmetic processing on the output data of the analog-digital conversion circuit 8 to generate image data by color signals, and then images by these color signals. Knee processing etc. are executed by the data.

The DSP 7 performs image data (hereinafter referred to as luminance data) DY corresponding to the luminance signal in these processes.
Is generated and output.

The automatic exposure control section 4 is constituted by, for example, a partial function of a controller that controls the operation of the electronic still camera 1. In this controller, by controlling the operation of the DSP 7 in response to various operations by the user, the image data DV is output to a display device (not shown) to display the image pickup result, and further the image data DV obtained by data compression is output. Is recorded on a predetermined recording medium.

In the automatic exposure controller 4, the detection circuit 11
Outputs the detection data DK by detecting the average value of the brightness data for each area set in the imaging result. Here, in this embodiment, one screen is divided in the horizontal direction and the vertical direction by a predetermined number of divisions to set a plurality of regions. Here, the finer the division number, the higher the detection accuracy of the backlight and the more division numbers are set within a practically sufficient range. In the detection circuit 11, the average value of the brightness levels is calculated for each area, the brightness level of each area is calculated, and the detection data DK is generated. Further, the detection circuit 11 sums the brightness levels of the respective areas calculated in this way and outputs the summed detection data together with the detection data DK.

The reference value calculation circuit 12 determines each region as a high-luminance region, a medium-luminance region, or a low-luminance region based on the sum of the luminance level of each region and the luminance level of each region based on the detection data DK thus obtained. Compute thresholds for classification into three categories. That is, when the image pickup result is divided into a plurality of areas and the distribution of the luminance level of each area is detected, in the general image pickup result, as shown in FIG. The result can be obtained. As a result, in a distribution result in which such a brightness level is widely and uniformly distributed, it can be determined that a so-called normal light state is present.

On the other hand, in the case of backlight, a distribution in which peaks are formed on the high luminance side and the low luminance side is detected as shown in FIG. As a result, when a distribution that is biased toward the high-luminance side and the low-luminance side is detected in this way, it can be determined that the backlight condition is present.

Based on this detection principle, the automatic exposure control section 4 classifies each area into three sections of a high brightness area, a middle brightness area, and a low brightness area to detect the distribution of brightness levels, and calculates a reference value. The circuit 12 calculates the threshold value for this classification.

That is, the reference value calculation circuit 12 determines the maximum value Yma from the brightness level of each area obtained from the detection circuit 11.
x and the minimum value Ymin are detected. Further, the reference value calculation circuit 12 similarly calculates the average brightness level Yave by dividing the total value of the brightness levels of the respective areas obtained from the detection circuit 11 by the number of areas. The reference value calculation circuit 12
With the maximum value Ymax, the minimum value Ymin, and the average brightness level Yave, a threshold value is set according to the brightness level distribution of the imaging result, and the brightness level of each area is classified.

Specifically, the reference value calculation circuit 12 has a difference value Δup (= difference between the maximum value Ymax and the average luminance level Yave).
Ymax-Yave) is calculated, and the difference value Δup is 1
A value Yave + Δup / 3 obtained by adding the value Δup / 3 of / 3 to the average brightness level Yave is set as the threshold value LH on the high brightness side. Similarly, the difference value Δdown (= Yave-Ym) between the minimum value Ymin and the average luminance level Yave.
ax), and the value Δ 1/3 of this difference value Δdown
The value Yave-Δdown / 3 obtained by subtracting down / 3 from the average brightness level Yave is set to the low brightness threshold value LL.

With this, the reference value calculation circuit 12 divides the maximum value Ymax and the average luminance level Yave, the minimum value Ymin and the average luminance level Yave into a predetermined ratio on the high luminance side and the low luminance side. Threshold L
Set to H and LL. The reference value calculation circuit 12 detects the threshold values LH and LL calculated in this manner as detection data D.
Output with K.

Subsequently, the luminance-by-luminance integrating circuit 13 sets the threshold value LH.
And LL are used as a reference to sequentially determine the signal level of the detection data DK, so that the brightness level of each region is set to high brightness,
Classify into medium brightness and low brightness. That is, the brightness-specific integration circuit 1
When the signal level of the detection data DK is higher than the high-luminance threshold value LH, 3 classifies the region corresponding to the detection data DK into the high-luminance region. When the signal level of the detection data DK is in the range of the high luminance threshold LH to the low luminance threshold LL, the region corresponding to this detection data DK is classified into the medium luminance region. When the signal level of the detection data DK is smaller than the low-luminance threshold value LL, the area corresponding to the detection data DK is classified into the low-luminance area.

Further, the luminance-specific integration circuit 13 counts the number of areas classified in this way for each classification. As a result, as shown in FIGS. 4 and 5, the brightness-specific integration circuit 13 causes the maximum value Yma of the brightness levels detected from the imaging result to be obtained.
The brightness level of each area is classified into high brightness, medium brightness, and low brightness by threshold values LH and LL set based on x, the minimum value Ymin, and the average value Yave, and the area set in the imaging result is used as a reference. Then, the area of each classification occupying the image pickup result is detected. Brightness-specific integration circuit 13
Outputs the count values S1, S2, S3 of the regions respectively belonging to the high brightness, the middle brightness, and the low brightness detected in this way to the subsequent backlight judgment circuit 14.

The backlight judgment circuit 14 judges whether or not there is backlight on the basis of the count values S1, S2, S3 of the areas respectively belonging to high brightness, medium brightness and low brightness thus detected. That is, as shown in FIG. 4 in comparison with FIG. 2, in the case of forward light, there is a characteristic that the luminance level is substantially uniformly and widely distributed in the imaging result, whereas in contrast to FIG. 3, it is shown in FIG. As described above, in the case of backlight, the brightness levels are unevenly distributed on the high brightness side and the low brightness side.

As a result, the backlight judgment circuit 14 causes the count values S1 and S of the areas belonging to high brightness and medium brightness, respectively.
2, it is determined whether the relationship of S1> k · S2 is established, and the relationship of S3> k · S2 is established between the count values S2 and S3 of the regions belonging to the middle luminance and the low luminance, respectively. However, when these relationships are established together, the determination result of backlight is output. Here, k is a predetermined constant.

That is, in the case of forward light as shown in FIG. 4, the brightness level is widely distributed, and the threshold is set by the maximum value, the minimum value and the average value of the brightness level obtained from this distribution. Therefore, in this case, S1≈S
The relationship of 2≈S3 can be obtained. As a result, it is possible to determine that the backlight is not present without satisfying any of the two relational expressions that are the criteria for determining the backlight.

On the other hand, in the case of the distribution as shown in FIG. 5, the brightness levels are unevenly distributed on the high brightness side and the low brightness side, so that the maximum value, the minimum value, and the average value of the brightness levels are used. Count value S obtained by setting the threshold value
1, S2, S3, S1> k · S2 and S3>
The relationship of k · S2 is established, and it can be determined that the backlight condition is present.

However, when a subject with different brightness is imaged with a full angle of view, for example, when a red and white flag is zoomed and imaged, the distribution of the brightness levels is changed to red and white as shown in FIG. There will be two corresponding brightness level peaks. In this case, in the case of setting the threshold value by the maximum value, the minimum value, and the average value of the brightness levels to classify the brightness levels and compare the areas,
The areas corresponding to these two colors are classified into high brightness and low brightness, respectively, and counted, so that S1> k · S2
, And S3> k · S2, both of which are satisfied, which results in an erroneous determination as a backlit state.

However, in such a case, there is a feature that the difference in the brightness level is small between the areas classified into the high brightness and the low brightness. As a result, the backlight determination circuit 14 determines the maximum value Ymax and the minimum value Ymin of the brightness level.
And the ratio Ymax / Ymin is calculated, and when this ratio is less than or equal to a predetermined value, S1> k · S2 and S3> k · S2 described above.
Even when the relationship of is established together, it is determined that the backlight is not in a backlit state.

Therefore, in this embodiment, the backlight judgment circuit 14 uses the coefficient k1 to calculate Ymax.
Only when the relations of / Ymin> k1, S1> k · S2, S3> k · S2 are both satisfied, it is judged that the backlight condition exists.
As a result, false detection of backlight is effectively avoided.

The control circuit 15 generates a predetermined determination reference value indicating the brightness of the image pickup result by processing the detection data DK based on the determination result DJ thus obtained, and this determination reference value is predetermined. The operations of the timing generator 3 and the digital-analog conversion circuit 6 are controlled so that the value becomes a value, and the automatic exposure control is thereby performed. That is, as shown in FIG. 7, the control circuit 15 sets the average value Yave of the brightness levels obtained by the processing of the detection data DK to the determination reference value when it is determined that the light is in the forward light state. The electronic shutter speed and the gain of the AGC circuit 5 are controlled so that the average value Yave becomes a predetermined value.

On the other hand, when the result of judgment that the light is backlit is obtained, as shown in FIG. 8, the low brightness is obtained by the selective addition process of the detection data DK based on the threshold LL on the low brightness side. The average value Ydave of the brightness level in the area classified into
Is calculated, and this average value Ydave is set as the determination reference value. Thus, in this case, the control circuit 15 controls the electronic shutter speed and the gain of the AGC circuit 5 so that the average value Ydave becomes a predetermined value as shown in FIG.

Accordingly, in this embodiment, C
The CD 2 constitutes the image pickup means for outputting the image pickup result, while the detection circuit 11 and the reference value calculation circuit 12 constitute the level detection means for detecting the maximum value, the minimum value and the average value of the brightness level of the image pickup result. To do. Further, the reference value calculation circuit 12 also constitutes threshold value setting means for setting a predetermined threshold value on the basis of the maximum value, the minimum value and the average value.
The luminance-by-luminance integrating circuit 13 constitutes a classifying unit that classifies the brightness level of the imaging result into a plurality of sections based on the threshold value based on the threshold value, and based on the classification by the classifying unit. Then, the area detection means for detecting the area of the imaging result belonging to each section is configured. Further, the backlight judgment circuit 14 constitutes a judgment means for judging the detection result by the area detection means to judge the backlight of the imaging result, and the control circuit 15 controls the exposure based on the judgment result of this judgment means. The control means is configured.

(1-2) Operation of the Second Embodiment With the above configuration, in the electronic still camera 1, C
The image pickup result obtained from the CD 2 is amplified by the AGC circuit 5 with a predetermined gain, converted into image data by the analog-digital conversion circuit 8, and this image data is subjected to knee processing, gamma processing and the like by the DSP 7. Electronic still camera 1
Then, the image data DV processed in this way is displayed on the display device, and is compressed and recorded on a predetermined recording medium.

In the electronic still camera 1, in these processes, the luminance data DY generated by the DSP 7 is set in units of areas generated by dividing one screen of the image pickup result.
Is detected as an average value, and the brightness level of each area is detected. Further, the control circuit 15 calculates an average value of the detection data DK, sets this average value as a judgment reference value for exposure control, and sets the judgment reference value to a predetermined value by an electronic shutter and an AGC. The process of automatic exposure control is executed.

That is, in the electronic still camera 1, when the image pickup result is too bright due to the evaluation reference value thus detected, the control circuit 15 controls the timing generator 3 so that the charge storage time in the CCD 2 is short. Is switched to. On the contrary, when the image pickup result is too dark, the charge generation time in the CCD 2 is switched to a long time by the same control of the timing generator 3 by the control circuit 15, and the brightness is also increased in this way. If it is insufficient, the gain of the AGC circuit 5 is increased, and the exposure result of the imaging is automatically adjusted so that the average brightness level of one screen in a unit of the area set in the screen becomes a predetermined value. (Fig. 7).

In the electronic still camera 1, the reference value calculation circuit 12 processes the detection data DK indicating the brightness level of each area in parallel with the above processing, and the brightness level of this area as a unit is detected. Maximum, minimum and average values are detected. Further, thresholds LL and LH that classify the brightness level into high brightness, medium brightness, and low brightness are set on the basis of the maximum value, the minimum value, and the average value thus detected (FIGS. 4 and 5). ). In the electronic still camera 1, the brightness-based integration circuit 13 that follows is based on the thresholds LL and LH.
The brightness level of each area is classified by, and the number of areas classified into high brightness, medium brightness, and low brightness is counted. As a result, the electronic still camera 1 classifies the brightness level of the imaging result into high brightness, medium brightness, and low brightness by the threshold values LL and LH based on the maximum value, the minimum value, and the average value of the brightness level in the imaging result. Then, the area of each classification is detected by the number of regions.

In the electronic still camera 1, the area of each classification thus detected is judged by the backlight judgment circuit 14 to judge whether it is backlight. That is, in the result of image capturing with forward light, the brightness levels are distributed almost uniformly (FIGS. 2 and 4), whereas in the case of backlight, a distribution biased to high brightness and low brightness is obtained (FIG. 3). And FIG. 5). As a result, in the electronic still camera 1, the area belonging to the high brightness level section and the area belonging to the low brightness level section respectively belong to other sections by determining whether or not a predetermined relational expression is satisfied. When it is larger than a predetermined value, the result of the judgment that the backlight is output is output. That is, in this embodiment, when the high-luminance area is a predetermined multiple of the medium-luminance area and the low-luminance area is a predetermined multiple of the medium-luminance area, the determination result of backlight is output.

As a result, in this embodiment, it is possible to effectively avoid the error determination of the backlight and detect the backlight.

That is, when the backlight level is simply determined by the predetermined threshold value and the backlight is detected, the backlight may be erroneously detected by classifying the brightness levels regardless of the distribution of the brightness levels in the imaging result. It was Specifically, as shown in FIG. 10, for example, when a light source or the like having an extremely high brightness level and a small size is imaged on the screen and the area of the medium brightness level is small, it is erroneously detected as backlight. To be done.

However, in this embodiment,
Threshold value L based on maximum, minimum, and average brightness levels
By setting L and LH, in the case as shown in FIG. 10, the average value becomes smaller, and the range of the brightness level classified as low brightness becomes smaller accordingly. The range of brightness levels classified into high brightness becomes wider, and accordingly, the classified areas S1, S2, and S3 of high brightness, medium brightness, and low brightness do not satisfy the above-described backlight judgment criterion. With this, in this embodiment, in the case of such a forward light, the false detection of the backlight is effectively avoided when the distribution of the middle luminance level is biased,
It is possible to remarkably improve the backlight detection accuracy as compared with the related art. In addition, it is possible to correctly detect the backlit state regardless of where the subject is placed on the screen.

Further, in this embodiment, in the case of such backlight determination, if the level difference between the maximum value and the minimum value of the brightness level is large due to the ratio of the maximum value and the minimum value of the brightness level, the above-mentioned condition is satisfied. When the level difference is small, it is determined that the backlight is not satisfied even if the above-described conditions are satisfied, and thus the false detection of the backlight can be effectively avoided.

When the backlight is judged by these, the electronic still camera 1 generates the evaluation reference value by the average brightness level of the part classified into the low brightness, and the judgment is made by the average value of the brightness levels of one screen of the image pickup result. Instead of the reference value, the exposure control is performed so that the evaluation reference value based on the low brightness becomes a predetermined value (FIG. 8), whereby an imaging result in which the subject is imaged by the backlight with appropriate brightness can be obtained. it can. As a result, in the image pickup result, it is possible to reliably suppress the blackout of the subject, which is picked up so as to be bright when the backlight is determined.

In the processing as described above, the electronic still camera 1 detects the maximum value, the minimum value and the average value, classifies the brightness level, calculates the area, calculates the evaluation reference value, etc. Backlight is detected with a smaller amount of calculation processing compared to the case where these processes are executed by all the pixels, by executing the process in units of a region divided by a predetermined number of divisions in the horizontal and vertical directions. Moreover, automatic exposure control can be performed.

(1-3) Effects of the First Embodiment According to the above configuration, the maximum value, the average value, and the minimum value of the brightness level are detected from the image pickup result, and the threshold value is set from these values. By classifying the brightness level by this threshold value and controlling the exposure, it is possible to detect the backlit state with higher accuracy than before.

Further, at this time, the maximum value, the minimum value, and the average value are detected in units of a plurality of regions formed by dividing the image pickup result in the horizontal direction and the vertical direction, respectively.
With simple processing, it is possible to detect the backlit state with higher accuracy than before.

Further, by classifying the brightness level of the image pickup result in units of a plurality of areas formed by dividing the image pickup result in the horizontal direction and the vertical direction, respectively, the brightness level of the image pickup result is higher than that of the conventional one. It is possible to detect the state of backlighting with accuracy.

Further, with a plurality of regions formed by dividing the image pickup result in the horizontal direction and the vertical direction, respectively, as a unit,
Also by detecting the area of the classified portion of each luminance, it is possible to detect the backlit state with higher accuracy by a simple process than before.

Further, by classifying the brightness levels according to the categories of high brightness, medium brightness, and low brightness, it is possible to classify the brightness levels according to the minimum level of classification necessary for this type of processing and obtain highly accurate detection results. Even in this case, it is possible to detect the backlit state with higher accuracy than in the past by a simple process.

When the area belonging to the high brightness level section and the area belonging to the low brightness level section are larger than the areas belonging to the other sections by a predetermined value or more, by outputting the judgment result of backlighting, By classifying the brightness levels in this way, it is possible to obtain a correct backlight determination result.

When the area belonging to the section having a higher brightness level and the area belonging to the section having a lower brightness level are larger than the areas belonging to the other sections by a predetermined value or more, and the maximum value and the minimum value are When the brightness level is high, the erroneous detection of backlight can be effectively avoided by outputting the determination result of backlight.

(2) Second Embodiment By the way, in the case where the threshold value is set by the maximum value, the minimum value and the average value of the brightness levels as described above, as shown in FIG. 9 by comparison with FIG. Even when the exposure control is performed so as to correct the backlight, the same classification result as in the case where the backlight is not corrected can be obtained in the classification of each section.

This means that even if the diaphragm or the like is corrected to correct the backlight, the state of the backlight is detected,
As a result, the exposure control can be stably performed by the exposure control in which the average value of low brightness is set as the determination reference value.

However, when the diaphragm or the like is corrected so as to correct the backlight and the brightness level is saturated in many areas, the brightness level division becomes different, which makes stable exposure control difficult. May become.

Therefore, in this embodiment, the luminance level to be processed is rounded down by a predetermined upper limit value so that the division of the luminance level does not differ even when the high luminance level is saturated by such backlight correction. The level to be cut off is variable according to the control value by the automatic light amount control.

According to this embodiment, the exposure level can be stably controlled by maintaining the brightness level division so as not to be different even when the area is saturated by the backlight correction.

(3) Other Embodiments In the above-described embodiment, the threshold value on the high luminance side is set to the maximum value side of the average value by 1/3 of the level difference between the maximum value and the average value. Set the level difference between the minimum value and the average value to 1
The case where the threshold value on the low luminance side is set to the minimum value side of the average value by the value of / 3 has been described, but the present invention is not limited to this, and the point is that such threshold value is set to the maximum value and the minimum value By setting the average value as a reference and reflecting the distribution of the brightness level in the imaging result in the classification of the brightness level, the value of 1/3 of such a difference value can be set to, for example, 1 /
It is possible to make various changes such as setting to 4, and it is also possible to appropriately switch the setting of such a threshold value by the setting of the photographing mode by the user.

Further, in the above-mentioned second embodiment,
Although the case where the division of the brightness level is maintained so as not to be different even by the saturation of the high brightness level due to the correction of the backlight due to the restriction of the brightness level has been described, the present invention is not limited to this, and the saturated amount is equivalent to Various methods can be widely applied, such as correcting the threshold value so that the sections do not differ.

In the above embodiment, the case where the brightness level is divided into three levels has been described, but the present invention is not limited to this, and the number of sections can be set variously as necessary.

Further, in the above-described embodiment, the maximum value and the like are detected with the region obtained by dividing the image pickup result in the horizontal direction and the vertical direction as a unit, the brightness level is classified, the area is calculated, and the evaluation reference value is calculated. However, the present invention is not limited to this, and in these processes,
It may be executed by setting areas different from each other, or may be executed in pixel units.

Further, in the above-described embodiment, the case where the evaluation reference value is set by the average value of the brightness levels has been described, but the present invention is not limited to this, and the image pickup result is divided in the horizontal direction and the vertical direction, for example. The present invention can be widely applied to the case where the evaluation reference value is set by weighted addition of brightness levels in units of area.

Further, in the above-described embodiment, the case where the backlight correction is performed so that the average value of the low luminance level becomes the predetermined value has been described. However, the present invention is not limited to this, and the comparison reference with the evaluation reference value is used. When the value setting is updated and backlight compensation is performed, when setting the evaluation reference value by weighting addition of the brightness level in units of the area obtained by dividing the imaged result in the horizontal and vertical directions, change the weighting coefficient. It can be widely applied to cases such as backlight correction.

Further, in the above-mentioned embodiments, the case where the present invention is applied to the image pickup device of the single plate type has been described, but the present invention is not limited to this and can be widely applied to the image pickup device of the three plate type. .

In the above embodiment, the case where the present invention is applied to an electronic still camera has been described.
The present invention is not limited to this, and is provided as an integrated type with an image pickup apparatus having a recording function such as a camera-integrated video tape recorder, an image pickup apparatus having a communication function such as a mobile phone, and a personal computer. It can also be widely applied to imaging devices and the like.

[0070]

As described above, according to the present invention, the maximum value, the average value, and the minimum value of the brightness level are detected from the image pickup result, the threshold value is set from these values, and the brightness level is determined by the threshold value. By classifying and controlling the exposure, it is possible to detect the backlit state with higher accuracy than before.

[Brief description of drawings]

FIG. 1 is a block diagram showing an electronic still camera according to a first embodiment of the present invention.

FIG. 2 is a characteristic curve diagram showing a distribution of brightness levels in a normal imaging result.

FIG. 3 is a characteristic curve diagram showing a distribution of brightness levels in an image pickup result under backlight.

FIG. 4 is a characteristic curve diagram for explaining setting of a threshold value in comparison with FIG.

5 is a characteristic curve diagram for explaining setting of a threshold value in comparison with FIG.

FIG. 6 is a characteristic curve diagram used to explain conditions for backlight detection.

FIG. 7 is a characteristic curve diagram for explaining exposure control in normal light.

FIG. 8 is a characteristic curve diagram for explaining backlight detection.

FIG. 9 is a characteristic curve diagram for explaining exposure control during backlighting.

FIG. 10 is a characteristic curve diagram for explaining erroneous detection of backlight.

[Explanation of symbols]

1 ... Electronic still camera, 2 ... CCD, 3 ... Timing generator, 4 ... Automatic exposure control unit, 5 ... A
GC circuit, 7 ... DSP, 11 ... Detection circuit, 12 ...
Reference value calculation circuit, 13 ... Luminance integration circuit, 14 ... Backlight determination circuit, 15 ... Control circuit

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2H002 DB27 DB29 DB31 HA04 JA07                 5C022 AA13 AB03 AB06 AB12 AC69                       CA00                 5C024 AX01 BX01 CX00 CX06 CX54                       GY01 HX18 HX23 HX28 HX30                       HX31 HX51

Claims (7)

[Claims] 1. An image pickup means for outputting an image pickup result, a level detection means for detecting a maximum value, a minimum value, and an average value of a brightness level of the image pickup result, and a reference value based on the maximum value, the minimum value, and the average value. A threshold value setting means for setting a predetermined threshold value, a brightness level of the imaging result, a classification means for classifying the brightness level into a plurality of categories based on the threshold value, and a classification by the classification means. , An area detection unit that detects an area of the imaging result belonging to each of the sections, a determination unit that determines a detection result by the area detection unit, and determines backlight of the imaging result, and a determination result of the determination unit. An image pickup apparatus comprising: a control unit that controls exposure as a reference. 2. The level detecting means detects the maximum value, the minimum value, and the average value in units of a plurality of regions formed by dividing the imaging result in the horizontal direction and the vertical direction, respectively. The image pickup apparatus according to claim 1, wherein the image pickup apparatus is provided. 3. The classifying means classifies the brightness level of the image pickup result in units of a plurality of regions formed by dividing the image pickup result in the horizontal direction and the vertical direction, respectively. Item 1. The image pickup device according to item 1. 4. The area detecting means detects the area in units of a plurality of regions formed by dividing the image pickup result in the horizontal direction and the vertical direction, respectively. The imaging device described. 5. The image pickup apparatus according to claim 1, wherein the classification by the classification means is a high-luminance, medium-luminance, or low-luminance classification. 6. The back light is determined when the area belonging to the high brightness level section and the area belonging to the low brightness level section are larger than the areas belonging to the other sections by a predetermined value or more. The imaging device according to claim 1, wherein a result is output. 7. The determining means is for a case where an area belonging to a section having a high luminance level and an area belonging to a section having a low luminance level are larger than respective areas belonging to other sections by a predetermined value or more, and The back light determination result is output when the difference in brightness level between the maximum value and the minimum value is large.
The imaging device according to.