JP2003319248A - Exposure control unit and monitoring camera apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To calculate a photometric value required for proper exposure control and to perform the exposure control based upon the photometric value. <P>SOLUTION: A maximum value and a minimum value of luminance signals from an image pickup part are calculated, discrete image pickup areas having luminance values within a fixed numerical value from the maximum value and discrete image pickup areas having luminance values within a fixed numerical value from the minimum value are respectively calculated, and it is decided at least which one of the total areas of the discrete respective image pickup areas occupies an area of the entire image pickup areas equally with or more than a prescribed ratio (108). When both the total areas do not occupy the area equally with or more than the prescribed ratio, exposure control (109 and 110) is performed based upon an averaged photometric value of luminance signals in the remaining image pickup areas except for the discrete respective image pickup areas. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvements in an exposure control device and a surveillance camera device that calculate a photometric value based on a luminance signal from an image pickup section and perform exposure control based on the photometric value.

[0002]

2. Description of the Related Art Conventionally, surveillance camera devices have been installed and used in various environments. In this type of surveillance camera device, a photometric method for calculating a photometric value required for exposure control is generally an average photometric method in which almost the entire area of the screen is measured and the average value of the luminance signal is used as the photometric value. It was target.

[0003]

However, despite the various environments in which the surveillance camera device is installed, most of the photometric methods for calculating the photometric value necessary for exposure control are as described above. Since it was a simple average metering system,
It had a problem that it could not fully cope with the various environments.

For example, in the open air, the white shirt of a person reflects sunlight to make a part of the screen very bright, or a part of the image on a sunny day has a shaded part so that the part of the screen is very bright. When the image is extremely dark, there is a problem that it is strongly influenced by the data of its characteristic portion and becomes too dark or too bright as compared with the image originally desired in the exposure control.

(Object of the Invention) An object of the present invention is to calculate a photometric value necessary for proper exposure control, and to provide an appropriate exposure correction based on the photometric value, and an exposure control device. An object of the present invention is to provide a surveillance camera device capable of recording an image with high image quality.

[0006]

In order to achieve the above object, the invention according to claims 1 to 5 calculates a maximum value and a minimum value of a luminance signal from an image pickup unit, and a constant numerical value from the maximum value. Each of the discrete imaging area having a brightness value within and the discrete imaging area having a brightness value within a fixed numerical value from the minimum value is detected, and at least one of the combined areas of the discrete imaging areas is at least one. It is determined whether or not it occupies a predetermined ratio or more with respect to the area of the entire imaging region, and if none of them occupies a predetermined ratio or more, the remaining imaging regions excluding the discrete imaging regions The exposure control device controls the exposure based on the averaged photometric value of the luminance signal.

In order to achieve the above-mentioned object, the invention according to claim 6 is provided with an image pickup section and a camera control section for converting an image photographed by the image pickup section into a digital signal. 7. A surveillance camera device having a recording device for recording the digital signal as image data, the surveillance camera device comprising the exposure control device according to claim 1 in the camera control section. .

In the above arrangement, the sum of the areas of the respective discrete image pickup areas having the luminance value within the fixed value from the maximum value and the minimum value of the luminance signal is a predetermined value with respect to the area of the entire image pickup area. If it does not occupy more than the ratio, it is assumed that the imaging region is a region having a specific luminance part, and the luminance signal of that region is not used for calculation of the photometric value, or on the other hand, the above condition is not satisfied, If the sum of the areas of any one of the discrete imaging areas occupies a predetermined ratio or more with respect to the area of the entire imaging area, the photometric value is calculated using the specific luminance portion of the imaging area, At the time of exposure control, the exposure is corrected by a predetermined amount.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will now be described in detail based on the illustrated embodiments.

FIG. 1 is a block diagram showing an electrical configuration of a surveillance camera device according to an embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a camera unit, which has a camera control unit 2, an image pickup unit 5, a buffer memory 9 and an image memory 10. The camera control unit 2 includes a control microcomputer 4, an image pickup unit driver 6, a video processing unit 7, an image data compression unit 8, and a USB-IF (interface) 11. An image data recording device 3 has a display device.

Next, the operation of the surveillance camera device having the above configuration will be described.

When the power is turned on and the system is started,
The image pickup unit driver 6 in the camera control unit 2 drives the image pickup unit 5, and the image pickup unit 5 outputs an image signal (video signal). This image signal is also output to the video processing unit 7 and the image data compression unit 8 in the camera control unit 2, where known signal processing and data compression are performed and converted into a digital signal. After that, the image data is output to the image data recording device 3 via the USB-IF 11 in the camera control unit 2, recorded in the image data recording device 3 as image data, and displayed on the display device.

Here, all the processing performed by the camera control unit 2 is performed by the camera control unit 2.
It is controlled by the control microcomputer 4 therein, and the details of the operation of the control microcomputer 4 will be described below with reference to FIGS. 2 to 4 according to the flowcharts of FIGS.

When a power source (not shown) is turned on and the surveillance camera device is activated, the control microcomputer 4 causes the control microcomputer 4 to perform step 100 in FIG.
From step 101 to step 101, the entire area within the visual field of the image pickup unit 5 is set as an image pickup area. Then, the next step 102
Included in the image signal output from the imaging unit 5,
The maximum value is calculated from the brightness signal data of the imaging region, and in the subsequent step 103, the minimum value is calculated from the brightness signal data of the imaging region output from the imaging unit 5. Next step 1
In 04, a constant numerical value including the maximum value and the minimum value calculated in steps 102 and 103, which is used to detect a discrete imaging region (group), is set to the maximum value based on a predetermined value. The value and the imaging region including the minimum value are determined so as not to overlap.

An example of this determination method will be described.

For example, the calculated maximum value is "190", the minimum value is "50", and the predetermined value used when deciding a constant numerical value to be used for detecting a discrete imaging region is "10". In this case, the imaging area including the maximum value is "181
The area having the value of "~ 190" and the image capturing area including the minimum value are areas having the value of "50 to 59", and the two image capturing areas do not overlap each other, so the certain numerical value is a predetermined value "10". It remains as it is.

On the other hand, for example, the calculated maximum value is "120", the minimum value is "103", and a predetermined value used when deciding a constant numerical value to be used for detecting a discrete imaging region is set. When "10" is set, the imaging area including the maximum value is an area having a value of "111 to 120", and the imaging area including the minimum value is an area having a value of "103 to 112". Since the areas having the values of “111 to 112” overlap, if each area is set excluding this overlapping area, the imaging area including the maximum value becomes “113 to 12”.
The image capturing area including “0” and the minimum value is “103 to 110”. Therefore, the constant value in this case is “8”.

Various methods are conceivable as the method of determining the constant numerical value, and the present invention is not limited to the above example.

Returning to FIG. 5, in the following step 105 and step 106, the control microcomputer 4 determines that the brightness signal data is a value within the predetermined constant value determined from the maximum value according to the calculated maximum value and minimum value. And a discrete imaging region in which the luminance signal data has a value within the fixed numerical value from the minimum value. Then, in the next step 107, the areas of the two image pickup regions are summed up, and in step 108 of FIG. 6, one of the detected two image pickup regions is added up. Of the entire image pickup area is 50% or more in advance (for example, 80%
%) Is determined to be exceeded.

As a result of the above determination, when it is determined that the total area of the two regions does not exceed the fixed ratio with respect to all the regions, the control microcomputer 4 executes step 108.
To step 109, as shown in FIG. 2, average value data is calculated from the luminance signal data of the remaining image pickup areas excluding the detected two image pickup areas, and in the subsequent step 110, the average value data is calculated. Exposure control is performed by using as a photometric value used for exposure control.

On the other hand, when it is determined that any of the added areas exceeds a certain ratio, the control microcomputer 4 proceeds from step 108 of FIG. 6 to step 201 of FIG.
Here, the imaging region determined to have an area exceeding a certain ratio is selected, and it is determined whether the selected imaging region is an imaging region having a value within the determined constant numerical value from the maximum value, If so, the process proceeds to step 202, and average value data is calculated from the luminance signal data of the selected imaging region, as shown in FIG. Then, in the next step 203, when the average value data is equal to or more than a predetermined value, it is determined to be bright, and the process proceeds to step 204, where the average value data is used as a photometric value used for exposure control and exposure control is performed. When performing, the exposure is positively corrected (for example, +1.5 correction) toward the small aperture side by a predetermined amount.

If it is determined in step 203 that the average value data is not equal to or larger than the predetermined value and it cannot be determined that it is bright, the process proceeds to step 205.
Exposure control is performed by using the average value data as it is as a photometric value used for exposure control.

If it is determined in step 201 of FIG. 7 that the selected image pickup area is an image pickup area having a value within the determined constant value from the minimum value, the process proceeds to step 206 of FIG. As shown in FIG. 4, average value data is calculated from the luminance signal data of the selected image pickup area. Then, in the next step 207, if the average value data is less than or equal to a predetermined value, it is determined that the image is dark, and the process proceeds to step 208, where the average value data is used as a photometric value used for exposure control and exposure control is performed. When performing, the exposure is negatively corrected by a predetermined amount (for example, -1.5).
to correct.

If it is determined in step 207 that the average value data is not equal to or less than the predetermined value and cannot be determined to be dark, the process proceeds to step 209, and the average value data is used as it is as a photometric value used for exposure control. Exposure control.

The above step 110 in FIG. 6, the steps 204 and 205 in FIG. 7, or the steps 208 and 209 in FIG.
When the operation of is finished, the control microcomputer 4 proceeds to step 111 of FIG. 6 in any case, determines whether the power is turned off here, and if not turned off, returns to step 102 of FIG. 5 and so on. Repeat the operation of. After that, when it is determined in step 111 of FIG. 6 that the power is off, the process proceeds to step 112, and the series of operations is ended.

In the above embodiment, when the luminance signal data from the image pickup unit 5 is input to the control microcomputer 4 via the image processing unit 7 of the camera control unit 2, the higher the numerical value, the brighter the lower numerical value. However, it is needless to say that the present invention can be applied to a case where a higher numerical value is darker and a lower numerical value is brighter.

According to the above embodiment, when calculating the photometric value required for exposure control based on the luminance signal from the image pickup unit 5, first, the maximum value and the minimum value of the luminance signal are calculated,
A discrete imaging area having a luminance value within a fixed numerical value from the maximum value and a discrete imaging area having a luminance value within a constant numerical value from the minimum value are respectively detected, and then the discrete imaging areas are summed up. It is determined whether or not at least one of the areas occupies a predetermined ratio or more (50% or more in the above example) with respect to the area of the entire imaging region. An averaged photometric value of the luminance signal in the remaining imaging regions excluding the discrete imaging regions is calculated, and exposure control is performed based on the photometric values (step 108 → step 1 in FIG. 6).
09 → step 110 (see also FIG. 2)), so that even if a part of the screen is abnormally bright or dark, an exposure control device that produces an image having a sufficient image quality level according to the monitoring purpose, It is possible to provide a surveillance camera device that records the image.

If at least one of the combined areas of the discrete image pickup regions occupies a predetermined ratio or more with respect to the total area of the image pickup region, the discrete image occupying the predetermined ratio or more. The exposure control is performed based on the averaged photometric value of the luminance signal of the image pickup area.

More specifically, when the discrete image pickup area is the image pickup area including the maximum value, it is determined whether or not the calculated averaged photometric value is brighter than a predetermined constant value. When the brightness is bright, the averaged photometric value is set as a photometric value necessary for exposure control, and when the exposure control is performed, the exposure is positively corrected by a predetermined amount (for example, +1.5).
(Correction) (step 108 of FIG. 6 → step 201 of FIG. 7 → step 202 → step 203)
→ Step 204 (see also FIG. 3)). Therefore, even when a part of the screen is abnormally bright, it is possible to provide an exposure control device that makes an image having a sufficient image quality level according to the monitoring purpose and a surveillance camera device that records the image.

When the discrete image pickup area is the image pickup area including the minimum value, it is determined whether or not the calculated averaged photometric value is darker than a predetermined constant value, When it is dark, the averaged value is used as a photometric value used for exposure control, and when performing exposure control, the exposure is negatively corrected by a predetermined amount (for example, -1.5 correction) ( Step 108 of FIG. 6 → FIG. 7
Step 201 → Step 206 in FIG. 8 → Step 2
07 → step 208 (see also FIG. 4)). Therefore, even when a part of the screen is abnormally dark, it is possible to provide an exposure control device that makes an image having a sufficient image quality level according to the monitoring purpose and a surveillance camera device that records the image.

The constant numerical value used when detecting a discrete imaging region including the maximum value and the minimum value is
Determined based on a predetermined value, provided that the areas including the maximum value and the minimum value do not overlap, and that an area having an intermediate value that does not belong to either area can be created. I am trying to do it.

[0033]

As described above, according to the present invention,
Provided are an exposure control device capable of calculating a photometric value required for proper exposure control and giving an appropriate exposure correction based on the photometric value, and a surveillance camera device capable of recording an image with a proper exposure image quality. It is possible.

[Brief description of drawings]

FIG. 1 is a block diagram showing an electrical configuration of a surveillance camera device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a first example of selection of an imaging region for calculating a photometric value and exposure correction in the embodiment of the present invention.

FIG. 3 is a diagram showing a second example of selection of an imaging region and exposure correction for calculating a photometric value in the embodiment of the present invention.

FIG. 4 is a diagram showing a third example of image pickup region selection and exposure correction for calculating a photometric value according to an embodiment of the present invention.

FIG. 5 is a flowchart showing a part of a schematic operation of the surveillance camera device according to the embodiment of the present invention.

FIG. 6 is a flowchart showing a continuation of the operation of FIG.

FIG. 7 is a flowchart showing a continuation of the operation of FIG.

FIG. 8 is a flowchart showing a continuation of the operation of FIG.

[Explanation of symbols]

1 camera section 2 Camera control section 3 Image data recording device 4 control microcomputer 5 Imaging unit 6 Imaging unit driver 7 Video processing unit 8 Image data compression unit 9 buffer memory 10 image memory

Claims (6)

[Claims] 1. A maximum value and a minimum value of a luminance signal from an image pickup unit are calculated, and a discrete image pickup area having a luminance value within a fixed numerical value from the maximum value and a luminance value within a fixed numerical value from the minimum value are provided. Each of the discrete imaging regions is detected, and it is determined whether at least one of the combined areas of the discrete imaging regions occupies a predetermined ratio or more with respect to the total area of the imaging regions. Does not occupy a predetermined ratio or more, the exposure control is characterized by performing exposure control based on an averaged photometric value of the luminance signal in the remaining image pickup regions excluding the discrete image pickup regions. apparatus. 2. When it is determined that at least one of the total areas of the discrete imaging regions occupies a predetermined ratio or more with respect to the entire area of the imaging region,
The exposure control device according to claim 1, wherein the exposure control is performed based on an averaged photometric value of the luminance signal of the discrete imaging region occupying a predetermined ratio or more. 3. When the discrete imaging area is an imaging area including the maximum value, it is determined whether the averaged photometric value is brighter than a predetermined value, and when it is bright, The exposure control apparatus according to claim 2, wherein the averaged photometric value is used as a photometric value required for exposure control, and the exposure is positively corrected by a predetermined amount when the exposure control is performed. 4. If the discrete imaging area is an imaging area including the minimum value, it is determined whether the averaged photometric value is darker than a predetermined value, and if it is dark, The exposure control device according to claim 2, wherein the averaged photometric value is used as a photometric value necessary for exposure control, and the exposure is negatively corrected by a predetermined amount when the exposure control is performed. 5. The constant numerical value used when detecting a discrete imaging region including the maximum value and the minimum value is such that the respective regions including the maximum value and the minimum value do not overlap each other, and The exposure control device according to claim 1, wherein the exposure control device is determined on the basis of a predetermined value that is determined on the condition that an area having an intermediate value that does not belong to the area can be created. 6. A surveillance camera having an image pickup section and a camera control section for converting an image photographed by the image pickup section into a digital signal, and a recording device for recording the digital signal from the camera control section as image data. In the apparatus, a surveillance camera device comprising the exposure control device according to any one of claims 1 to 5 in the camera control unit.