JP2002369074A - Exposure controller for optical equipment and its program and its method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the exposure controller of optical equipment, its program, and its method capable of holding an exposure correction value stably and performing smooth exposure correction even when it is largely changed. SOLUTION: A system control part 9 prepares a brightness histogram from the exposure evaluation information of each evaluation small area obtained by dividing a photographic picture area into 100 pieces of 10×10, and sets a reference block for deciding whether or not exposure correction should be executed when a block position X where the n-th data from the brightest data are present in the blocks of the prepared brightness histogram is smaller than any other block. When a photographic picture is bright, whether or not the block position X is smaller than the reference block is judged. When it is judged that the block position X is smaller, the information of the block position X (the block number of the block position X and the exposure correction value there) in this time exposure evaluation is stored in block position information 111. Then, the exposure correction value is averaged the set number of times so that the exposure correction value can be decided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an exposure control apparatus, a program, and a method for an optical apparatus using an image sensor, such as a digital video camera and a digital still camera.

[0002]

2. Description of the Related Art Conventionally, photometric methods such as average photometry, center-weighted photometry, spot photometry, and multi-pattern photometry have been used as automatic exposure determination methods in an exposure control device of an optical device such as a video camera. In such an automatic exposure determination method, a plurality of evaluation areas are set in advance in a captured image area, and exposure is determined using average luminance information of each evaluation area (including the entire captured image).

FIG. 4 is a block diagram showing a configuration example of a conventional video camera. Hereinafter, an outline of a conventional video camera will be described with reference to FIG.

As shown in FIG. 4, a conventional video camera comprises a lens (optical system) 1, an aperture 2, a CCD 3, and a CCD.
DS4, process processing circuit 5, A / D converter 6,
Aperture control unit 7, CCD drive unit 8, system control unit 9
, A digital signal processing unit 10, a memory 11, an image data processing unit 12, a memory card 13, an image display processing unit 14, and an image display unit 15.

[0005] Light from a subject passes through a lens (optical system) 1 and an aperture 2 to form an image on a CCD 3, and the amount of light formed by the CCD 3 is converted into an electric signal and output as an image signal. . The output image signal is subjected to gain control in the process processing circuit 5 after noise of the CCD 3 is removed by the CDS 4, and is converted to a digital signal by the A / D converter 6 because it is an analog signal.

An aperture control unit 7 is connected to the aperture 2, and a CCD driving unit 8 is connected to the CCD 3. The aperture control unit 7 is controlled by the system control unit 9,
By opening and closing the hole diameter of the aperture 2, the diameter of the light beam incident from the lens 1 and reaching the CCD 3 is changed. Also, C
The CD drive unit 8 is controlled by the system control unit 9. The CCD 3 accumulates electric signals (accumulates electric charges) by the light from the subject, and the CCD driving unit 8 extracts the electric signals thus accumulated at specified timings.
3 is controlled. That is, the CCD 3 performs a shutter operation (a so-called electronic shutter) under the control of the CCD driving unit 8. As described above, the aperture control unit 7 and the CCD drive unit 8 control image capturing with various exposures.

[0007] Image information for one image on the CCD 3 (electrical signal from the CCD 3 for one electronic shutter) is sent to the CDS 4 and then to the A / D converter 6 via the process processing circuit 5 as described above. Sent. The A / D converter 6 converts the received image information (analog signal) for one image into a digital signal and sends the digital signal to the digital signal processing unit 10. The digital signal processing unit 10 performs RGB signal conversion and image interpolation. Perform digital image processing. The image data (luminance signal) thus created by the digital signal processing unit 10 is once sent to the memory 11 and then sent to the image data processing unit 12 for image processing such as gamma correction and compression. Output and stored. The image data created by the digital signal processing unit 10 is sent to an image display processing unit 14 and subjected to image display processing such as γ processing, and then sent to an image display unit 15 such as an LCD monitor. The photographed image is confirmed by the image display unit 15.

Next, an evaluation area set in advance in the photographed image area will be described with reference to FIGS. As described above, a plurality of evaluation areas are set, such as the entire captured image, and the minimum unit is referred to as an evaluation small area in this specification.

FIG. 5 shows a photographed image area of 10 × 10 × 10.
The small evaluation area divided into zero and the evaluation area (areas 1 to 6 surrounded by a thick line) formed by combining the small evaluation areas
(Part) is a diagram showing an example. The luminance integrated value of the small evaluation area is processed by the digital processing unit 10, and the processing for each evaluation area is performed by the system control unit 9. This is to make it easy to change the shape of the area under evaluation (how to combine the small evaluation areas) depending on the situation.

FIG. 6 is a diagram showing an example of setting an evaluation area when center-weighted photometry is performed. Exposure control is performed based on photometric data from two evaluation areas surrounded by hatched portions. Exposure control is performed by giving weight to the evaluation area close to the center of the two evaluation areas. General. When spot metering is performed, exposure control is performed based on photometric data from an evaluation area that is the same as or smaller than the evaluation area near the center shown in FIG. It is effective to arrange the evaluation area at the center of the image as shown in FIG. 6 when there is not much difference in brightness, but there is a case where correction processing called high brightness processing is performed on an image having a large difference in brightness. In order to solve the problem associated with the high luminance processing, there has been proposed a method of moving a region under evaluation for performing center-weighted photometry or spot photometry depending on the state of an image.

Next, referring to FIG. 7, in an image having a large luminance difference, an evaluation area is arranged at the center of the image by the above-described center-weighted photometry or spot photometry, and exposure control is performed using high luminance processing. The problem will be described.

FIG. 7A is a diagram modeling a landscape photograph of a mountain or the like. In FIG. 7A, the sky, which is considerably brighter than the lower mountain or the ground, is located almost upward from the center of the screen. Here, since the high-luminance sky is also located at the center of the screen, the luminance of the sky has a large effect when center-weighted photometry or spot photometry is performed.
As shown in (a), the whole image is dark. That is, in order to obtain a bright image as shown in FIG. 7B, some kind of correction such as high luminance processing is required.

As a method of the high luminance processing, it is general to replace the luminance with a high luminance prescribed value (including 0) which is determined for a high luminance portion which is equal to or higher than a predetermined threshold (hereinafter, referred to as a high luminance threshold). However, if the high-luminance threshold for determining the high-luminance portion is fixed, the high-luminance portion does not exist depending on the situation, and the high-luminance processing may not be performed. As described below, the manner of occurrence of this problem depends on whether the light incident on the lens changes from a dark state to a bright state or from a bright state to a dark state.

For example, when exposure control is continuously performed to display an image on an LCD monitor or the like, FIG.
If the camera moves from the state where the image center is directed to a dark ground portion as shown in FIG. 7C to the angle of view as shown in FIG. 7B, the camera is exposed to the dark ground portion in FIG. Therefore, in the state of FIG. 7B, the sky portion becomes higher than the high brightness threshold value, and the high brightness process is performed. However, when the center of the image faces the sky as shown in FIG. 7 (d), the camera is brought into a state as shown in FIG. Is not determined as a high-luminance part in the image even if the direction of the image changes, and as a result, a dark image as shown in FIG. 7E is output without performing high-luminance processing. Become.

Although an example in which automatic exposure correction is continuously performed for display on an LCD monitor or the like has been described, coarse adjustment and fine adjustment are performed when actual shooting is performed without continuous exposure control. For example, since the exposure evaluation for the exposure control is performed by changing the exposure several times, the same occurs even if the exposure control is not continuous.

Here, the number of exposure evaluations for exposure control is not always 30 frames / second, which is generally used for display, even in the case of display on an LCD monitor or the like as described above. This is a problem of the processing capability of a computer. Generally, even if continuous exposure control is performed, the number of times is less than 30 times per second.

Next, a problem in a case where the luminance distribution is concentrated will be described with reference to FIGS. The problem is that there are notes and calendars with text, snow scenes,
It occurs when shooting a signboard with a bright color background,
This occurs particularly when an image containing a large number of white (accurately achromatic) portions is captured. FIG. 8 is a diagram illustrating an example of an image in which characters, bright photographs, and the like are placed on a white background.
FIG. 9 is a diagram illustrating an example of a luminance histogram created by the system control unit 9.

FIG. 8A is a diagram showing an example in which characters are written on a white background. When photographing a sheet of paper as shown in FIG. 8A, for example, a notebook on which characters are written, the background of the notebook (white background) is large, and the exposure of the notebook matches the background of the notebook. FIG. 8B is a diagram showing an example of a calendar in which a bright photograph is placed on a white background. In this case as well, the control of exposure is greatly affected by the background (white background).

FIG. 9A is a diagram showing an example of a luminance histogram in an image having a large luminance difference including the sky as shown in FIG. 7 described above. In general exposure control, exposure is controlled such that the center of such a luminance distribution is a center section of the luminance histogram. In FIG. 7, the vicinity of section number 2 which is intermediate between the low-luminance part (ground) and the high-luminance part (sky) in the luminance histogram of FIG. 9A is the center of the luminance distribution. ) Will result in a slightly darker image.

FIG. 9B is a diagram showing an example of a luminance histogram in an image having a large white background as shown in FIG. In the case of FIG. 9B, since the luminance distribution is concentrated on the section number 4 which is a white background, this section number 4 is the center of the luminance distribution in general exposure control. That is, the exposure is controlled so that a white background (accurately, an achromatic color having a high luminance) becomes gray in appearance. Similarly, snow scenes have many white parts, so when a snow scene is photographed, the snow parts become gray and the whole image becomes a dark image.

In the above example, the case where white is large has been described.
If the background or the background is a bright color and occupies a large area with almost the same luminance distribution, the exposure will match the background or the background part (the background or the background part will be the center of the luminance distribution) Therefore, even if the color is not white in particular, the screen also becomes dim. Among them, white tends to be more remarkable because of its high brightness, and when people look at it, if the white part looks gray, it is more likely to feel uncomfortable, so that white does not appear gray. A way was needed.

Therefore, a brightness histogram is created, and it is determined whether or not a high-luminance portion is included in the brightness distribution. By performing the exposure correction to make the white portion look as white as possible, an exposure for suppressing the entire image from being dim is performed. Control devices are conventionally used.

Next, the operation of a conventional exposure control device that performs exposure correction using a luminance histogram will be described with reference to FIG. FIG. 10 is a flowchart showing the operation of the conventional exposure control device.

First, the system controller 9 creates a luminance histogram (step S1). Here, as shown in FIG. 5, the brightness histogram indicates that the captured image area is 10 × 10 1
It is created from the exposure evaluation information for each of the evaluation small areas divided into 00 pieces. In this specification, the exposure evaluation information is a general term for information used for determining exposure, such as a luminance signal of each evaluation small area and information used for exposure control.

As shown in FIG. 5, when the evaluation area is divided, the number of elements of the histogram (the number of small evaluation areas) is 100.
Since there is only one pixel, the width per section in the luminance, which is the horizontal axis of the luminance histogram, cannot be made too narrow. This is because if the width per section is reduced, the total number of sections increases, and the frequency at which the luminance of each evaluation small area enters per section decreases. Therefore, the sensitivity of the CCD is ± 3 ev (Expousure
Value) Considering before and after, the width per section is set to 1.0 ev. The number of sections is 9 in consideration of correction such as exposure correction. The unit of the section is ev
It has been found that the unit is less susceptible to the effect of the high luminance portion.

When the exposure evaluation information of the small evaluation area is output as a linear value, the histogram is created by converting the threshold value for each section when creating the histogram from the ev value into a linear value. For example, if the linear data at the time of the target exposure (exposure when the center of the histogram becomes the center of the luminance distribution when uniform light is captured) is 1000, the histogram section (see FIG. In the following, it is indicated by the center value).

[0027]

[Table 1]

When the luminance histogram is created, the threshold value of the section is shifted by an amount of correction such as exposure correction by the user, so that the same luminance histogram is always obtained even when the amount of correction changes. You may.

A reference section for determining whether correction is to be performed when the section in which the n-th data from the brightest data exists among the sections of the created luminance histogram is smaller than any of the sections (step S2). That is,
The preset reference section is shifted by the exposure correction amount at the time of shooting. Actually, we set the reference section without correction to 5, but in the previous processing, -1 ev
Is corrected, the reference section is also shifted by 1 ev and changed to section number 6. The processing before that is, for example, correction by user setting, correction with a model having a backlight determination function, plus correction for preventing grayish when there are many achromatic portions, and the like.

FIG. 11 shows an example in which the reference section is shifted when such correction is applied. FIG. 11A shows the created luminance histogram (before correction), and FIG. 11B shows the luminance histogram after correction of +1.0 ev (after correction). When the total exposure correction amount is +1.0 ev, the reference section is also set to +1 and in FIG. 11B, the section number 5 is the reference section. Thus, the reference section also changes according to the total exposure correction amount.

Further, as shown in FIG. 11, the section in which the n-th data exists is obtained from the brightest data, so that the portion of the image where a part of the image becomes bright due to reflection of light from a window, metal, or the like is obtained. The effects can be removed.
The value of n (a predetermined threshold) is preferably set to 10% or less of the total number of regions. We have set it at 5%.

It is determined whether or not the image currently being processed is a bright image based on the exposure conditions and the like (step S).
3) In the case of a dark image (step S3; NO), the correction by the high luminance processing is not performed (step S3).
4). This is to prevent black ones from becoming gray by the plus correction. This determination is not simply made based on the overall brightness, but is made in a complex manner including the brightness of the achromatic portion.

If the image is bright (step S3; Y
ES), the section position X in which the nth (predetermined threshold count) data (evaluation small area) from the brightest in the luminance histogram is found (step S5).
Specifically, the frequency numbers included in the sections starting from the brighter one are added, and the section address at the time when the total becomes n is X.

It is determined whether or not the section number of the section position X obtained in step S4 is smaller than the section number of the reference section set in step S2 (step S6). When the section number of the section position X is smaller (step S6; Y
ES), the process proceeds to a process of setting an exposure correction amount. If the exposure correction amount is large (step S6; NO), the exposure correction amount is set to 0 to make no correction (step S4).

When the section number of the section position X is smaller than the section number of the reference section (step S6; YES), the section number between the reference section set in step S2 and the section position X obtained in step S4 is determined. The exposure correction amount is set based on the difference between the brightness values indicated by the difference (step S7). As for the setting of the exposure correction amount, a preset exposure correction amount is used, such as an exposure correction amount of -1 ev when the difference between the luminance values is 0 ev and -2 ev when the difference is 1 ev.

Based on the exposure correction amount thus set, exposure evaluation information for controlling the exposure is created, and the system control unit 9 uses the exposure evaluation information to control the aperture control unit 7 and C
A function unit that performs exposure control such as the CD drive unit 8 is controlled, and exposure control is performed.

Here, as a first prior invention example similar to the present invention in the technical field, in the technique disclosed in Japanese Patent Application Laid-Open No. 5-122600, a luminance signal above a preset clip level is set as an upper limit. Is converted into a luminance signal of the clip level thus obtained. The clip level is selected based on the photometry information from two types that are set in advance.

Further, in the technique disclosed in Japanese Patent Application Laid-Open No. Hei 7-298131, which is similar to the present invention and is similar to the prior art example 2 in the technical field, light data (signals) from the optical system are set in advance. The high brightness signal exceeding the threshold value is removed, and exposure control is performed based on the remaining high brightness removal signal.

Further, as a prior invention example 3 similar to the present invention in the technical field, in the technique disclosed in Japanese Patent Application Laid-Open No. 10-322592, a preliminary photographing is performed, and the brightness of the image data at the time of the preliminary photographing is calculated. By calculating a difference between the maximum value and the minimum value and creating a brightness histogram based on the calculated difference in brightness, a gradation characteristic that makes it difficult for the high brightness region to be saturated is calculated. The image signal is corrected based on the calculated gradation characteristics.

In the technique disclosed in Japanese Unexamined Patent Application Publication No. 11-32236, which is similar to the invention of the prior application in the technical field of the present invention, in the technique disclosed in Japanese Patent Laid-Open Publication No. Is detected, and γ correction is performed in accordance with the size of the peak pattern, and at the same time, processing for preventing image quality deterioration due to γ correction is performed.

[0041]

As described above, in the conventional exposure control apparatus, the high-brightness portion is replaced with a certain brightness or excluded to evaluate the exposure to evaluate the high-brightness portion such as a sky portion. Can be suppressed to some extent. However, when the proportion of the high-brightness part such as the sky occupies the image part increases, the influence of the high-brightness part increases, and as a result, the sky is exposed and the image becomes dark as a whole. Has occurred. In general, exposure control is performed so that the average luminance at the time of photographing is close to the center of the photographing luminance range. For example, when photographing white paper such as a notebook, the exposure control is performed so that the white portion is at the center of the luminance range. Would. For this reason, the image is photographed as if it were slightly dark and grayish. The problem that white becomes gray occurs in the same way when shooting a snow scene, and there is a problem that the image is shot as if the snow part was gray and the entire image is dark.

Further, in the conventional exposure control apparatus which performs exposure correction using the luminance histogram shown in the flowchart of FIG. 10, in step S4, the partition position X where the n-th data from the brightest one exists is obtained. If the first data is the partition position X-1 or the (n-1) th data is the partition position X + 1, the exposure correction amount changes due to a slight shift in the angle of view. In particular, when the difference in the exposure correction amount between the sections is large, a phenomenon called hunting occurs in which the monitor screen or the like becomes brighter or darker.

In the first and second prior art examples, a brightness histogram is prepared and exposure correction is forcibly applied only by simple exposure correction so that a high brightness portion is not used. To make it look white instead of gray. However, when the angle of view changes due to camera shake or zoom, the above-mentioned problem that the exposure correction value is not stable and the monitor screen may be bright or dark is similar. A similar problem arises.

Further, in the prior art examples 3 and 4, gradation correction and gamma correction are performed using a luminance histogram. However, it takes time to perform gradation correction and gamma correction processing by a program, and hardware Doing so would be costly.

The present invention has been made in view of such circumstances, and has the following objects. The first object is to reduce the influence of the hunting as described above as much as possible by storing in a memory or the like the section position X up to a plurality of previous exposure evaluations. That is, when the range in which data is present is detected using the luminance histogram and the exposure correction is performed using the detected histogram, the exposure correction amount is kept as stable as possible, and even when the exposure correction amount greatly changes, An object of the present invention is to provide an exposure control device, a program, and a method for an optical device that can perform exposure correction.

The second object is to determine the exposure correction amount using the luminance information of the white background (achromatic color) portion of the background, thereby achieving stable exposure correction without unnaturally changing the density of the white background portion in the image. An object of the present invention is to provide an exposure control apparatus, a program, and a method for an optical device that can be performed.

A third object of the present invention is to make it possible to perform exposure control according to the present invention when necessary in an optical apparatus that can be programmed.

[0048]

To achieve the above object, the present invention has the following features. According to a first aspect of the present invention, there is provided an image pickup unit for converting an image obtained by light incident from an optical system into an electric signal, a signal processing unit for converting an electric signal converted by the image pickup unit into a luminance signal, and a plurality of images. And a luminance integrating means for integrating the luminance signal for each of the areas, and combining the luminance integrated value calculated by the luminance integrating means by an arbitrary method, and exposing to an exposure evaluation value for evaluating the exposure. Evaluation means, and exposure control means for controlling exposure with the exposure evaluation value converted by the exposure evaluation means, wherein the exposure evaluation means creates and creates a luminance histogram composed of a plurality of sections based on the luminance integrated value. The frequency count is accumulated and counted from the high-luminance side or the low-luminance side of the obtained luminance histogram, and the luminance integrated value at which the counted frequency number becomes a predetermined threshold value In an exposure control apparatus of an optical apparatus for changing an exposure correction amount using a first section position of a luminance histogram including data, a storage section for storing the first section position by a preset number of exposure evaluations. Wherein the exposure evaluation means calculates the exposure evaluation value based on the preset number of first division positions.

According to a second aspect of the present invention, there is provided an achromatic color detecting means for detecting whether or not the area divided by the luminance integrating means is close to an achromatic color. A luminance histogram (hereinafter referred to as an achromatic color histogram) is created using only the luminance integrated value of the detected area, and the frequency counts are accumulated and counted from the high luminance side or the low luminance side of the achromatic color histogram. Is characterized in that the exposure correction amount is changed using the second section position of the achromatic color histogram including the data of the luminance integrated value that becomes a predetermined threshold value.

According to a third aspect of the present invention, in the first aspect of the invention, the exposure evaluating means calculates an average value of the exposure correction amount at the first division position for a preset number of times, and calculates an exposure correction value in the exposure evaluation value. It is characterized by the amount.

According to a fourth aspect of the present invention, there is provided an image pickup means for converting an image obtained by light incident from an optical system into an electric signal, a signal processing means for converting the electric signal converted by the image pickup means into a luminance signal, The image is divided into a plurality of regions, and a luminance integrating unit that integrates a luminance signal for each of the regions, and a luminance integrated value calculated by the luminance integrating unit are combined in an arbitrary manner to form an exposure evaluation value for evaluating exposure. An exposure control program for causing an optical apparatus including: an exposure evaluation unit to convert; and an exposure control unit to control exposure by the exposure evaluation value converted by the exposure evaluation unit to execute the following processing, and Processing to create a brightness histogram composed of multiple sections based on the frequency histogram, and counting the frequency by accumulating the frequency from the high brightness side or the low brightness side of the created brightness histogram. And, counted frequency number contains data of luminance integrated value as a predetermined threshold value,
Processing for calculating a first section position of the luminance histogram;
The optical device includes a process of storing the first section position for a preset number of exposure evaluations and an exposure evaluation process of calculating an exposure evaluation value based on the preset section position for the preset number of times. Is executed.

According to a fifth aspect of the present invention, there is provided an achromatic color detecting process for detecting whether an area divided by a luminance integrating means is close to an achromatic color, and a luminance integrating process for detecting an achromatic color by the achromatic color detecting process. A process of creating a luminance histogram (hereinafter, achromatic histogram) using only the values, a method of accumulating and counting the frequency numbers from the high luminance side or the low luminance side of the achromatic color histogram, and setting the counted frequency number to a predetermined threshold And changing the exposure correction amount based on the second section position of the achromatic color histogram including the data of the integrated luminance value.

According to a sixth aspect of the present invention, in the fourth aspect of the present invention, the exposure evaluation processing is performed by calculating an average value of the exposure correction amount at the first division position for a preset number of times, and calculating the exposure correction value at the exposure evaluation value. It is characterized by the amount.

According to a seventh aspect of the present invention, there is provided an image pickup means for converting an image obtained by light incident from an optical system into an electric signal, a signal processing means for converting the electric signal converted by the image pickup means into a luminance signal, The image is divided into a plurality of regions, and a luminance integrating unit that integrates a luminance signal for each of the regions, and a luminance integrated value calculated by the luminance integrating unit are combined in an arbitrary manner to form an exposure evaluation value for evaluating exposure. An exposure control method for an optical device comprising: an exposure evaluation unit for converting; and an exposure control unit for controlling exposure by an exposure evaluation value converted by the exposure evaluation unit, the exposure control method comprising: a plurality of sections based on a luminance integrated value. A luminance histogram is created, and the frequency numbers are accumulated and counted from the high luminance side or the low luminance side of the created luminance histogram. A first section position of a luminance histogram including data of a luminance integrated value serving as a predetermined threshold is calculated, and the first section position is stored for a predetermined number of times of exposure evaluation, and a predetermined number of times is calculated. The exposure evaluation value is calculated based on the first division position of the minute.

The invention according to claim 8 is a method for detecting whether or not an area divided by the luminance integrating means is close to an achromatic color, and using only the integrated luminance value of the area detected as an achromatic color to obtain a luminance histogram (hereinafter, achromatic color). Histogram), and counts by accumulating frequency numbers from the high-luminance side or low-luminance side of the achromatic histogram, and includes the data of the integrated luminance value at which the counted frequency number becomes a predetermined threshold. The exposure correction amount is changed based on the second section position of the histogram.

According to the ninth aspect of the present invention, when calculating the exposure evaluation value, an average value of the exposure correction amounts at the first division positions for a preset number of times is set as the exposure correction amount in the exposure evaluation value. It is characterized by the following.

[0057]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an exposure control apparatus, a program, and a method for an optical apparatus according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing a configuration example of a video camera to which the exposure control device according to the present invention is applied.
Note that the same reference numerals are used for the same components as those in FIG.
The detailed description is omitted.

As shown in FIG. 1, a video camera as an embodiment of the present invention has a lens (optical system) 1 and an aperture 2.
, CCD3, CDS4, process processing circuit 5,
A / D converter 6, aperture control unit 7, CCD drive unit 8
, A system control unit 9, a digital signal processing unit 10,
It comprises a memory 11, an image data processing unit 12, a memory card 13, an image display processing unit 14, and an image display unit 15. The memory 11 stores section position information 111.

The digital signal processing section 10 performs a luminance integration process for each evaluation small area. This is performed by converting the RGB signal data included in the electric signal from the small evaluation area into a luminance value, and integrating the luminance value for each small evaluation area. The luminance integrated value for each evaluation small area is sent to the system control unit 9, and the system control unit 9 performs each processing according to the present invention such as creation of a histogram (luminance histogram) based on a luminance distribution, and determines an exposure correction amount.
Then, an exposure evaluation value for performing exposure control is obtained based on the exposure correction amount and the exposure condition at the time of shooting, and the exposure control is performed by controlling the CCD driving unit 8 and the aperture control unit 7 based on the exposure evaluation value. Do it.

When a video camera control program is written in the memory card 13, when a special operation is performed on the video camera, the video camera control program is transferred to a camera control program memory (not shown) and the camera control program can be rewritten. it can. Thus, by using the storage medium storing the exposure control program for the optical device according to the present invention, the processing according to the present invention can be performed as necessary. Note that the exposure control program may be stored in advance in a camera control program memory (not shown) of the main body instead of the storage medium such as the memory card 13.

The memory 11 stores section position information 111. It is assumed that the section position information 111 includes the above-described section number of the section position X and the exposure correction amount for the preset number of exposure evaluations. The system control unit 9 calculates the exposure evaluation value used for the above-described exposure control by averaging the exposure correction amount of the section position X by the number of times of the preset exposure evaluation.

Next, the operation of the video camera exposure control apparatus according to the embodiment of the present invention will be described with reference to FIG. FIG. 2 is a flowchart showing an operation example of the exposure control device according to the present invention. The operation up to step S6 is the same as the operation of the conventional exposure control device shown in FIG.

If it is determined in step S6 that the section number of the section position X is smaller than the section number of the reference section, the section number between the reference section set in step S2 and the section position X obtained in step S4 is determined. Based on the difference between the brightness values indicated by the difference, the system control unit 9 sets the section position X in the current exposure evaluation and the exposure correction amount there (step S7). As for the setting of the exposure correction amount, a preset exposure correction amount is used similarly to the conventional exposure control device.

The information of the section position X (the section number of the section position X and the exposure correction amount there) in the current exposure evaluation set in this way is transmitted to the section position information 11 by the system control section 9.
1 (step S8). Since the section position information 111 stores the information on the section position X up to the set number of times before, the exposure correction amount is determined by averaging the exposure correction amounts for the set number of times (step). S
9). That is, the information of the section position X in the exposure evaluation before the set number of times is sequentially deleted every time the exposure evaluation is performed once.

The method of determining the exposure correction amount using the section position information 111 will be described in more detail with reference to FIG. FIG. 3 is a diagram illustrating an example of the section position information 111. Here, it is assumed that the number of exposure evaluations stored in the section position information 111 is set to eight.

FIG. 3A is a diagram showing an example of the section position information 111 when the section position X changes minutely each time. The correspondence between the section number of the section position X and the exposure correction amount thereat is shown in the [Correspondence to Exposure Correction Amount] table. Even when the section position X changes finely each time, the average value of the eight exposure correction amounts calculated from the latest exposure evaluation up to seven times before is calculated, and the average value is used as the actual exposure value. This is an exposure correction amount for calculating exposure evaluation information used for control. By calculating the exposure correction amount based on the exposure evaluation each time, the exposure correction value calculated as shown in FIG. 3A remains -1.5 ev even when the division position X changes minutely each time. Becomes
A stable image with little hunting can be obtained.

FIG. 3B is a diagram showing an example of the section position information 111 when the section position X changes under the influence of a slight panning or zooming of the video camera. The correspondence between the section number of the section position X and the exposure correction amount thereat is shown in the [Correspondence to Exposure Correction Amount] table. In this case, similarly to the case of FIG. 3A, 8 calculated from the latest exposure evaluation up to seven times before.
The average value of the exposure correction amounts for the batches is determined, and the average value is used as the exposure correction amount for calculating exposure evaluation information used for actual exposure control. By calculating the exposure correction amount in each exposure evaluation in this way, even when the section number of the section position X changes from 4 to 5, the exposure correction amount is stepwise from -2.0 ev to -1.0 ev. , And the brightness can be gradually changed without the screen suddenly becoming brighter or darker.

Next, a description will be given of a method of performing exposure control with priority given to an achromatic color portion when the video camera as an embodiment of the present invention has an achromatic color detection function.

This method uses a video camera to shoot an object such as a calendar shown in FIG. 8B in which a photograph and a character are mixed in a white background. In order to prevent a change in the angle of view, zoom, and the like, and to prevent a change in the actually photographed density of the white background portion due to the influence, correction is performed to keep the white background portion at a certain brightness.

Here, the achromatic color detection function means that the digital signal processing unit 10 uses the R signal included in the electric signal from the small evaluation area.
When the RGB signal data is converted to a luminance value, the function detects an achromatic portion by color discrimination using the RGB signal data. Since this achromatic color detection method is a known method, a detailed description thereof will be omitted. In addition, a reference to be determined as an achromatic portion is set in advance. That is, an evaluation small area closer to an achromatic color than previously set is determined as an achromatic color portion. The criterion for determining the achromatic portion may be changed by a user input.

In the method using the achromatic color detection function, first, a luminance histogram (hereinafter referred to as an achromatic color histogram) is created using only the luminance integrated value of the small evaluation area detected as achromatic by the achromatic color detection function. From the achromatic color histogram, the above-described section position X is obtained.

Here, the partition position X is determined by a method that does not use the achromatic function described above, that is, a method that generates a luminance histogram for all luminance information included in the electric signal from the CCD. The position calculated from the achromatic color histogram by the method using the achromatic function is referred to as a second position. That is, the operation using the section position X described with reference to the flowchart shown in FIG.
The partition position X is the first partition position when using all the luminance information, and the partition position X is the second partition position when using only the achromatic portion luminance information.

The information on the section position X (second section position) in the current exposure evaluation thus calculated is stored in the section position information 111 in step S8 of the flowchart of FIG. 2, and the exposure correction amount is determined in step S9. Is done. That is, an exposure evaluation is performed using only an exposure correction amount each time a white background portion is white with respect to the luminance of the evaluation small region determined to be achromatic, and an exposure correction amount for calculating an exposure evaluation method used for exposure control is calculated. I will decide. With this method, it is possible to maintain a stable density with respect to the density of the white background portion, and even when the brightness changes, the density gradually changes without suddenly brightening or darkening the white background portion. Can be

The above-described method of performing exposure control by giving priority to the achromatic portion is performed when the ratio of the small evaluation area determined to be achromatic to the entire screen exceeds a predetermined ratio. It is good. If the brightness (brightness) of the evaluation small area determined to be achromatic is darker (lower brightness) than a predetermined value, the portion is considered to be black, Exposure correction for a colored portion may not be performed. In addition, when some setting regarding exposure is performed by the user, the above-described exposure correction for the achromatic portion may not be performed in order to give priority to correction according to the user's intention.

In the embodiment of the present invention, the calculation of the exposure correction amount used for the exposure control is described as averaging the exposure correction values based on the exposure evaluation for a set number of times. The processing method is not limited to only the average, and another statistical processing method may be used.

In the embodiment of the present invention, the partition position X
Has been described as finding the section in which the n-th data exists from the brightest one in the luminance histogram, but it is also possible to count not only from the brighter one but also from the darker one. At this time, it is preferable that the value of n be 90% or more of the total number of regions.

Further, in the embodiment of the present invention, the setting of the evaluation small area and the area under evaluation is described as the setting shown in FIG. 5, but is not limited thereto, and may be other settings.

Further, in the embodiment of the present invention, the luminance histogram used for exposure control is described as having a width per section of 1 ev and a number of sections of 9 as shown in FIG. However, the present invention is not limited to this section width or the number of sections, and may be another section width or another number of sections.

Further, in the embodiment of the present invention, the number of exposure evaluations stored in the section position information 111 is described as eight, but the number is not limited to this and may be set to any number.

In the embodiment of the present invention, the photographed image is described as being stored in the memory card 13, but the storage medium is not limited to the memory card.
For example, a video tape may be used. At this time, the memory card storing the control program is set in the video camera separately from the storage medium for storing images.

Further, in the embodiments of the present invention, the exposure control device of the optical device is described as an exposure control device of a video camera. However, the present invention is not limited to the optical device using an image pickup device. A scope using a camera or a CCD may be used.

[0083]

As is apparent from the above description, according to the exposure control apparatus, the program, and the method of the optical apparatus of the present invention, the division position X up to a plurality of previous exposure evaluations is stored in a memory or the like. By doing so, it is possible to obtain an image with a stable exposure that is less affected by hunting. That is, when a range in which data exists is detected using a luminance histogram and exposure correction is performed using the range,
The exposure correction amount can be kept as stable as possible, and smooth exposure correction can be performed even when the exposure correction amount greatly changes.

Further, according to the exposure control apparatus, the program, and the method of the optical apparatus of the present invention, the exposure correction amount is determined using the luminance information of the white background (achromatic color) of the background, so that the white background in the image It is possible to perform stable exposure correction without unnaturally changing the density.

Further, according to the exposure control apparatus, the program, and the method of the optical device of the present invention, the exposure control according to the present invention can be performed when necessary in an optical device that can be programmed.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration example of a video camera to which an exposure control device according to the present invention is applied.

FIG. 2 is a flowchart showing an operation example of the exposure control device according to the present invention.

FIG. 3 is a diagram showing an example of section position information 111.

FIG. 4 is a block diagram illustrating a configuration example of a conventional video camera.

FIG. 5 is a diagram illustrating an example of a small evaluation area and a middle evaluation area in a captured image area;

FIG. 6 is a diagram showing a setting example of an evaluation area when center-weighted photometry is performed.

FIG. 7 is a diagram illustrating an example of an image having a large luminance difference.

FIG. 8 is a diagram illustrating an example of an image in which characters, bright photographs, and the like are placed on a white background.

FIG. 9 is a diagram illustrating an example of a luminance histogram.

FIG. 10 is a flowchart showing the operation of a conventional exposure control device.

FIG. 11 is a luminance histogram showing an example in which a reference section is shifted when exposure correction is applied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Lens (optical system) 2 Aperture 3 CCD 4 CDS 5 Process processing circuit 6 A / D converter 7 Aperture control unit 8 CCD driving unit 9 System control unit 10 Digital signal processing unit 11 Memory 12 Image data processing unit 13 Memory card 14 Image display processing unit 15 Image display unit 111 Block position information

Claims (9)

[Claims] An imaging unit configured to convert an image obtained by light incident from an optical system into an electric signal; a signal processing unit configured to convert an electric signal converted by the imaging unit into a luminance signal; A luminance integrating unit that divides the region into regions and integrates the luminance signal for each of the regions; combining the luminance integrated values calculated by the luminance integrating unit by an arbitrary method and converting the integrated values into an exposure evaluation value for evaluating exposure Exposure evaluation means, and exposure control means for controlling exposure based on the exposure evaluation value converted by the exposure evaluation means, wherein the exposure evaluation means comprises a luminance histogram composed of a plurality of sections based on the luminance integrated value. Is created, and the frequency numbers are accumulated and counted from the high brightness side or the low brightness side of the created brightness histogram, and the counted frequency numbers are calculated in advance. An exposure control device for an optical apparatus that changes an exposure correction amount using a first section position of the luminance histogram, the data including the data of the integrated luminance value that is a determined threshold value; Storage means for storing a predetermined number of exposure evaluations, wherein the exposure evaluation means calculates the exposure evaluation value based on the first division position for the predetermined number of times. Exposure control device for optical equipment. 2. An achromatic color detecting means for detecting whether the area divided by the luminance integrating means is close to an achromatic color, wherein the exposure evaluating means is detected as an achromatic color by the achromatic color detecting means. A luminance histogram (hereinafter referred to as an achromatic color histogram) is created using only the luminance integrated value of the region, and the frequencies are accumulated and counted from the high luminance side or the low luminance side of the achromatic color histogram. 2. The exposure of the optical apparatus according to claim 1, wherein the exposure correction amount is changed using a second partition position of the achromatic color histogram that includes data of the luminance integrated value that becomes a predetermined threshold value. Control device. 3. The exposure evaluation unit according to claim 2, wherein the exposure evaluation unit sets an average value of the exposure correction amounts at the first division positions for the preset number of times as an exposure correction amount in the exposure evaluation value. An exposure control device for an optical apparatus according to claim 1. 4. An image pickup means for converting an image obtained by light incident from an optical system into an electric signal; a signal processing means for converting an electric signal converted by the image pickup means into a luminance signal; A luminance integrating unit that divides the region into regions and integrates the luminance signal for each of the regions; combining the luminance integrated values calculated by the luminance integrating unit by an arbitrary method and converting the integrated values into an exposure evaluation value for evaluating exposure An exposure control program for causing an optical device including: an exposure evaluation unit to perform the following processing; and an exposure control unit to control exposure by the exposure evaluation value converted by the exposure evaluation unit. A process of creating a brightness histogram composed of a plurality of sections based on the values, and a frequency count from a high brightness side or a low brightness side of the created brightness histogram. A process of calculating a first section position of the luminance histogram, including data of the luminance integrated value that is accumulated and counted and the counted frequency number becomes a predetermined threshold value; and the first section position. A process of storing the exposure evaluation value for a preset number of times, and an exposure evaluation process of calculating the exposure evaluation value based on the preset number of the first division positions. An exposure control program for an optical device. 5. An achromatic color detecting process for detecting whether the area divided by the luminance integrating means is close to an achromatic color, and only the luminance integrated value of the area detected as an achromatic color by the achromatic color detecting process. Creating a luminance histogram (hereinafter referred to as an achromatic color histogram), accumulating and counting the frequency numbers from the high luminance side or the low luminance side of the achromatic color histogram, and the counted frequency number is a predetermined threshold value 5. The optical device according to claim 4, wherein the process of changing an exposure correction amount based on a second partition position of the achromatic color histogram including the data of the integrated luminance value is performed. 6. Exposure control program for optical equipment. 6. The exposure evaluation process according to claim 1, wherein an average value of the exposure correction amounts at the first division positions for the preset number of times is set as an exposure correction amount in the exposure evaluation value. An exposure control program for an optical device according to item 4. 7. An image pickup means for converting an image obtained by light incident from an optical system into an electric signal; a signal processing means for converting an electric signal converted by the image pickup means into a luminance signal; A luminance integrating unit that divides the region into regions and integrates the luminance signal for each of the regions; combining the luminance integrated values calculated by the luminance integrating unit by an arbitrary method and converting the integrated values into an exposure evaluation value for evaluating exposure An exposure control method for an optical device, comprising: an exposure evaluation unit that performs exposure control; and an exposure control unit that controls exposure based on an exposure evaluation value converted by the exposure evaluation unit. The frequency histogram is created from the high brightness side or the low brightness side of the created brightness histogram and counted. Calculating a first division position of the luminance histogram, including the data of the luminance integration value at which the recording frequency is a predetermined threshold value; An exposure control method for an optical device, wherein the exposure evaluation value is calculated based on the first division positions for the preset number of times. 8. A luminance histogram (hereinafter, referred to as an achromatic color histogram) using only the luminance integrated value of the region detected as an achromatic color by detecting whether the area divided by the luminance integrating means is close to an achromatic color. The number of frequencies is accumulated and counted from the high luminance side or the low luminance side of the achromatic histogram, and the counted frequency number includes data of the luminance integrated value that is a predetermined threshold. The exposure control method for an optical device according to claim 7, wherein the exposure correction amount is changed based on the second section position of the achromatic histogram. 9. When calculating the exposure evaluation value, an average value of the exposure correction amount at the first division position for the preset number of times is set as an exposure correction amount in the exposure evaluation value. The exposure control method for an optical device according to claim 7, wherein