JP3624434B2 - Exposure amount control device - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to an exposure amount control apparatus suitable for use in a video camera apparatus.
[0002]
[Prior art]
2. Description of the Related Art Today, video camera devices that capture images using an image sensor such as a CCD or an imaging tube are in widespread use.
In the video camera device, an illuminance detection unit detects the illuminance of the imaging screen, and an exposure amount control device for controlling the exposure amount is provided based on the detection result, and the exposure amount is controlled by the exposure amount control device. However, imaging is performed by the imaging element.
[0003]
The illuminance detection unit detects the illuminance on the imaging screen by detecting the illuminance at the center of the imaging screen on the assumption that the subject is photographed at the center of the imaging screen.
[0004]
[Problems to be solved by the invention]
By the way, in the illuminance detection means for detecting the illuminance at the center of the imaging screen, the illuminance at the center is detected from the subject when the subject is shot out of the center of the imaging screen due to movement of the subject or camera shake. Since it changes to the background, the detected illuminance changes greatly.
[0005]
For this reason, the illuminance of the imaging screen photographed while the exposure amount is controlled based on the detection result of the illuminance at the central portion is greatly changed, resulting in an unsightly image.
Even when the subject is located at the center of the imaging screen, the background illumination is too strong in the backlit state when the illuminance in the area other than the center is considerably brighter than the illumination in the center. There was a problem that the image became overexposed.
[0006]
Even when the subject is located at the center of the imaging screen, the background illuminance is dark when the illuminance of the area other than the center is considerably dark compared to the illuminance at the center. There was a problem that the background was crushed black too much.
In view of such problems, an object of the present invention is to provide an exposure amount control apparatus that controls an appropriate exposure amount regardless of shooting conditions.
[0007]
[Means for Solving the Problems]
An exposure amount control apparatus according to the present invention includes an illuminance detection unit that detects illuminance per unit area of an upper portion, a peripheral portion, and a central portion of an imaging screen, and a periphery with respect to the detected illuminance at the central portion that is detected by the illuminance detection unit. An exposure reference value setting means for variably setting an exposure reference value based on a first ratio determined by the detected illuminance of the part and a second ratio determined by the detected illuminance of the peripheral part with respect to the detected illuminance of the upper part, Exposure amount control means for controlling the exposure amount according to the difference between the exposure reference value set by the exposure reference value setting means and the detected illuminance at the center detected by the illuminance detection means, and the exposure reference value setting The means is characterized in that the exposure reference value is set larger as the first ratio increases, and the exposure reference value is set smaller as the second ratio goes away from the standard value.
[0008]
In the exposure amount control apparatus according to the present invention, the exposure amount control means controls the exposure amount by varying at least one of the aperture amount, the shutter speed, and the gain of the AGC amplifier.
[0009]
[Action]
In the exposure control apparatus according to the present invention, the exposure reference value setting means sets the exposure reference value to be larger as the first ratio determined by the detected illuminance at the peripheral portion with respect to the detected illuminance at the central portion detected by the illuminance detecting means increases. In addition, the exposure reference value is set to be smaller as the second ratio determined by the detected illuminance at the peripheral portion with respect to the detected illuminance at the upper portion is away from the standard value. The exposure amount is variably set according to the difference between the exposure reference value set by the exposure reference value setting means and the detected illuminance at the center detected by the illuminance detection means. The exposure amount is controlled by at least one variable setting of an aperture amount, a shutter speed, and a gain of the AGC amplifier.
[0010]
【Example】
A preferred embodiment of an exposure control apparatus according to the present invention will be described below with reference to the drawings. The exposure amount control apparatus according to the present invention is provided for controlling the exposure amount of a video camera apparatus as shown in FIG.
The video camera apparatus shown in FIG. 1 provided with the exposure amount control apparatus uses a CCD image sensor 53 as an image sensor.
[0011]
This video camera apparatus includes an objective lens 51 that guides a subject image to the video camera body, an iris 52 that adjusts the amount of illuminance from the subject image, and a CCD image sensor 53 that guides the subject image via the iris 52. The AGC amplifier 54 that adjusts the gain of the imaging signal so that the level of the imaging signal is constant regardless of the change in illuminance of the subject image supplied to the CCD image sensor 53, and the AGC amplifier 54 that is supplied from the AGC amplifier 54 An A / D converter 55 for A / D converting the gain-adjusted imaging signal, a signal processing circuit 56 for image processing of the A / D converted imaging signal supplied from the A / D converter 55, and the iris The exposure amount is controlled by controlling the aperture amount 52, the shutter speed of the CCD image sensor 53, and the gain of the AGC amplifier 54. And a exposure amount control unit 10.
[0012]
The exposure amount control apparatus 10 according to the present invention shown in FIG. 1 includes an illuminance detection means 1 that detects the illuminance of an imaging screen from an A / D converted imaging signal supplied from the A / D converter 55, and Based on the detected illuminance supplied from the illuminance detecting means 1, the exposure reference value setting means 2 for variably setting the exposure reference value, and the exposure amount according to the exposure reference value supplied from the exposure reference value setting means 2 Exposure amount control means 3 for controlling.
[0013]
The illuminance detection means 1 is configured to be able to detect the illuminance per unit area within each frame of the upper part A, the peripheral part B, and the central part C of the imaging screen 50 as shown in FIG.
The illuminance detection means 1 integrates the luminance of each scanning line for each field in each frame of the upper part A, the peripheral part B, and the central part C of the imaged signal in the captured image 50, thereby integrating all the pixels in each frame. The integrated illuminance of the area is detected, and the integrated illuminance detected for each frame is divided by the area of each part to detect the average illuminance per unit area of each part.
[0014]
When the horizontal direction of the captured image 50 is a length x on the X axis and the vertical direction is a length y on the Y axis, for example, the upper part A shown in FIG. / 4 y to y. Further, the central portion B has a width from 2 / 5x to 3 / 5x and a length from 2 / 5y to 3 / 5y. Further, the peripheral part B is an area excluding the upper part A and the central part C.
The exposure reference value setting means 2 includes a detection illuminance determination circuit 21 that determines the illuminance state of photographing based on the detection illuminance detected by each unit detected by the illuminance detection means 1, and the determination result of the detection illuminance determination circuit 21. A modulation coefficient memory 22 from which the modulation coefficient K is read, a weight setting circuit 23 in which a weight for weighting the modulation coefficient K is preset according to the specifications of the video camera or the exposure amount control device 10, and the modulation coefficient K And a multiplication circuit 24 that multiplies the weights to obtain an exposure reference value.
[0015]
The detected illuminance determination circuit 21 divides the detected illuminance of the peripheral portion B of the captured image 50 detected by the illuminance detection means 1 by the detected illuminance of the central portion C, and the detected illuminance of the peripheral portion B. The division value P2 divided by the detected illuminance at the upper part A is calculated, converted into converted values Q1 and Q2 based on the divided values P1 and P2, and an illuminance determination which is a multiplication value of the converted value Q1 and the converted value Q2 The value R is configured so that the illuminance state of photographing can be determined.
[0016]
As shown in FIG. 3, the illuminance state by the division values P1 and P2 is determined as the standard region S when the division value P1 is near 1, and is determined as the backlight region T when the division value P1 is greater than 1, and is divided. When the value P1 is smaller than 1, it is determined as the over-order light region U. Further, as the division value P2 becomes larger than 1 or smaller than 1, it is determined to weaken the backlight in the backlight region T or the excessive light in the excessive light region U.
[0017]
In the detected illuminance determination circuit 21, as shown in FIG. 4, the division value P1 is converted into a conversion value Q1 that increases as the division value P1 increases. Based on this conversion value Q1, the illuminance state of photographing is determined to be a standard state in the vicinity of the division value P1 = 1, and it is determined that the backlight becomes stronger as the division value P1 becomes greater than 1, and the division value P1 is greater than 1. It is determined that the over-order light has become stronger as it becomes smaller.
[0018]
When the division value P1 is 4 or more, it is determined that the backlight is too strong, and the conversion value Q1 that is the conversion value of the division value P1 is set to a constant value of 255. When the division value P1 is 0.25 or less, it is determined that excessive forward light is too strong, and the conversion value Q1 that is the conversion value of the division value P1 is set to a constant value of zero.
Further, in the detected illuminance determination circuit 21, as shown in FIG. 5, the division value P2 becomes 1 when the division value P2 is in the range of 0.5 to 2, and the division value P2 increases from 2 or increases. As the value P2 decreases from 0.5, the converted value Q2 is reduced. Based on this conversion value Q2, the illuminance state of photographing is determined to be a standard state when the division value P2 is in the range of 0.5 to 2, and converted so as to reduce the backlight as the division value P2 becomes larger than 2, As the division value P2 becomes smaller than 0.5, it is determined and converted so that excessive forward light is reduced.
[0019]
As described above, the detected illuminance determination circuit 21 obtains the division value P1 and the division value P2 based on the detection illuminance of each unit supplied from the illuminance detection means 1, and the division value P1 is 4 or more or 0.5 or less. At this time, the conversion value Q1 of the division value P1 is kept constant, and when the division value P2 is 2 or more or 0.5 or less, the conversion value Q2 of the division value P2 decreases.
[0020]
The conversion value Q1 and the conversion value Q2 are multiplied with each other to obtain an illuminance determination value R. The illuminance determination value R is converted into a logarithmic modulation coefficient K as shown in FIG. The modulation coefficient K is associated with the illuminance determination value R and stored in advance in the modulation coefficient memory 22, and the modulation coefficient K is set according to the illuminance determination value R supplied from the detected illuminance determination circuit 21. The modulation coefficient memory 22 is configured to be readable.
[0021]
The exposure amount control means 3 includes a comparison circuit 31, a phase compensation circuit 32 that compensates for the phase delay of the signal due to the transmission of the exposure reference value setting means 2 and the comparison circuit 31, and the illuminance difference whose phase has been compensated. A control amount calculation circuit 33 that calculates a control signal for controlling the exposure amount, an iris drive circuit 34 that variably drives the iris amount of the iris 52, and a shutter speed of the CCD image sensor 53 based on the control signal. A shutter driving circuit 35 for driving and a D / A converter 36 for D / A converting a signal supplied to the AGC amplifier 54 are provided.
[0022]
The comparison circuit 31 includes an exposure reference value and an illuminance detection unit 1 that are variably set so as to suppress a backlighting state and an over-ordering state of photographing in accordance with the photographing illuminance state supplied from the exposure reference value setting unit 2. The difference in illuminance, which is the difference in the detected illuminance at the central portion C detected in step (1), can be calculated.
As described above, the exposure amount control device 10 provided in the video camera device according to the present invention is the illuminance per unit area of the upper part A, the peripheral part B, and the central part C of the imaging screen 50 by the illuminance detection means 1. The exposure reference value setting means 2 divides the detected illuminance at the peripheral portion B by the detected illuminance at the central portion C and the detected illuminance at the peripheral portion B by the detected illuminance at the upper portion A. Based on the division value P2, the exposure reference value is variably set, and the exposure amount control means 3 controls the exposure amount according to the difference between the exposure reference value and the detected illuminance at the central portion C.
[0023]
A backlight state that increases as the illuminance of the peripheral portion B with respect to the central portion C increases with the division value P1, and when the division value P1 is 4 or more, the conversion value Q1 of the division value P1 is a constant value. Keep on. Also, a backlight condition that increases as the illuminance of the peripheral part B with respect to the upper part A increases is determined based on the division value P2, and when the division value P2 is 2 or more, the conversion value Q2 of the division value P2 is determined. Decrease.
[0024]
For this reason, the illuminance determination value R, which is a product of the conversion value Q1 and the conversion value Q2, is formed so that the illuminance of the background of the subject is suppressed, and the exposure amount control means 3 and the illuminance determination value R and the center Based on the difference in detected illuminance of part C, it is possible to sufficiently suppress the backlight state by controlling the exposure amount so as to suppress the illuminance of the background of the subject.
Further, even in an over-ordered light state, an over-ordered light state that increases as the illuminance of the peripheral part B with respect to the central part C decreases is determined by the division value P1, and the division value P1 is 0.25 or less. Therefore, the conversion value Q1 of the division value P1 is kept constant. Further, a backlight state that increases as the illuminance of the peripheral part B with respect to the upper part A decreases is determined by the division value P2, and when the division value P2 is 0.5 or less, a conversion value Q2 of the division value P2 is set. Decrease.
[0025]
For this reason, the illuminance determination value R, which is a product of the conversion value Q1 and the conversion value Q2, is formed so as to suppress the illuminance of the subject, and the exposure amount control means 3 and the illuminance determination value R and the central portion C are formed. Based on the difference in detected illuminance, it is possible to control the exposure amount so as to suppress the illuminance of the subject and sufficiently suppress the over-order light state.
In the present embodiment, the case where the exposure control device is used in the video camera device using the CCD image sensor as the image pickup device is shown, but the present invention is not limited to such a video camera device. The exposure amount control apparatus of the present invention can also be applied to the case where another image pickup device such as an image pickup tube is used as the image pickup device.
[0026]
In the present embodiment, the exposure amount control unit controls the exposure amount by changing the aperture amount, shutter speed, and gain of the AGC amplifier. However, the present invention is limited to such an exposure amount control unit. However, the exposure amount control apparatus of the present invention is also applicable to the case where the exposure amount control means controls the aperture amount by varying at least one of the aperture amount, the shutter speed, and the gain of the AGC amplifier. is there.
[0027]
Further, in the present embodiment, the case where the imaging screen 50 is divided into three as shown in FIG. 2 by the illuminance detection means is shown, but the present invention is not limited to such illuminance detection means, and the present invention In the exposure amount control apparatus, there are three or more illuminance measurement regions by the illuminance detection means, and the position of the measurement region, the size of the measurement region, and the shape of the measurement region are the same as the exposure amount control device The present invention can also be applied to a case where the setting is made in accordance with the specification of the video camera device provided with the device.
[0028]
【The invention's effect】
As described above in detail, the exposure amount control apparatus of the present invention increases the exposure reference value as the first ratio determined by the detected illuminance at the peripheral portion with respect to the detected illuminance at the central portion detected by the illuminance detecting means increases. An exposure reference value setting means for setting the exposure reference value to be smaller as the second ratio determined by the detected illuminance of the peripheral portion with respect to the detected illuminance of the upper portion deviates from the standard value. The exposure amount can be variably set according to the difference between the exposure reference value set by the means and the detected illuminance at the center detected by the illuminance detecting means. For this reason, according to the present invention, the exposure amount is controlled so as to suppress the illuminance of the background of the subject during backlighting and to suppress the illuminance of the subject during excessive forward light, so that the exposure amount is always controlled normally. An exposure amount control device can be provided.
[0029]
The exposure amount can be controlled by at least one variable setting of the aperture amount, the shutter speed, and the gain of the AGC amplifier. Therefore, it is possible to provide an exposure amount control device that always controls the exposure amount normally in video camera devices of various specifications.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a schematic configuration of a main part of a video camera apparatus provided with an exposure amount control apparatus according to the present invention.
FIG. 2 is a schematic configuration diagram of an imaging screen of a video camera device provided with the exposure amount control device, showing an upper part, a peripheral part, and a central part of the imaging screen.
FIG. 3 is an illuminance state diagram at the time of photographing with respect to a divided value P1 obtained by dividing the detected illuminance at the peripheral part by the detected illuminance at the central part and a divided value P2 obtained by dividing the detected illuminance at the peripheral part by the detected illuminance at the upper part;
FIG. 4 is a characteristic diagram of a conversion value Q1 with respect to the division value P1.
FIG. 5 is a characteristic diagram of a conversion value Q2 with respect to the division value P2.
FIG. 6 is a characteristic diagram of a modulation coefficient K with respect to an illuminance determination value R that is a multiplication value of the division value P1 and the division value P2.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Illuminance detection means 2 Exposure reference value setting means 3 Exposure amount control means 50 Imaging screen

Claims (2)

Illuminance detection means for detecting the illuminance per unit area of the upper part, the peripheral part, and the central part of the imaging screen;
Based on the first ratio determined by the detected illuminance of the peripheral part with respect to the detected illuminance of the central part detected by the illuminance detection means, and the second ratio determined by the detected illuminance of the peripheral part with respect to the detected illuminance of the upper part Exposure reference value setting means for variably setting the exposure reference value;
Exposure amount control means for controlling the exposure amount according to the difference between the exposure reference value set by the exposure reference value setting means and the detected illuminance at the center detected by the illuminance detection means ,
The exposure reference value setting means sets the exposure reference value larger as the first ratio increases, and sets the exposure reference value smaller as the second ratio departs from the standard value. and exposure amount control device. The exposure amount control means, aperture size, shutter speed, and by varying either at least one of the gain of the AGC amplifier exposure amount control apparatus according to claim 1, wherein the controlling the amount of exposure.

Images