Method and apparatus for controlling exposure of video camera
First Claim
Patent Images
1. An exposure control apparatus comprising:
- an image sensor for picking up a scene and generating video signals;
adjusting means for adjusting an exposure amount of said image sensor;
evaluating means for evaluating a time sequential change of said video signals corresponding to at least two different areas in a pick-up frame of said image sensor; and
speed changing means for changing a control speed of said adjusting means in response to a signal generated from said evaluating means depending on whether or not a change in the scene has occurred.
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Abstract
An exposure control apparatus receives a video signal from a scene pick-up image sensor and performs a divided brightness measuring for an image free. In accordance with the brightness distribution or a change amount of a scene obtained by the divided brightness measuring, the adjustment speed for a diaphragm is switched. In another embodiment, a scene brightness value for use as the exposure control is corrected to thereby obtain a smooth exposure control for continuous scenes. Scene pick-up by panning is detected by a built-in acceleration sensor in a video camera. Therefore, if the video camera is moved abruptly, then the exposure control is made slowly.
140 Citations
15 Claims
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1. An exposure control apparatus comprising:
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an image sensor for picking up a scene and generating video signals; adjusting means for adjusting an exposure amount of said image sensor; evaluating means for evaluating a time sequential change of said video signals corresponding to at least two different areas in a pick-up frame of said image sensor; and speed changing means for changing a control speed of said adjusting means in response to a signal generated from said evaluating means depending on whether or not a change in the scene has occurred. - View Dependent Claims (2, 3, 4, 5, 6)
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7. An exposure control apparatus for a video camera comprising:
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an image sensor for picking up a scene and generating a video signal; adjusting means for adjusting an exposure amount of said image sensor; an acceleration sensor for measuring an acceleration applied to said video camera; and speed changing means for changing a control speed of said adjusting means in response to a signal generated from said acceleration sensor. - View Dependent Claims (8)
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9. An exposure control method for a video camera which picks up a scene with an image sensor by converting an optical image into video signals, comprising the steps of:
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measuring average brightness photometric values respectively of a plurality of areas in accordance with said video signals corresponding to each of said areas by dividing a pick-up frame of said image sensor into said plurality of areas; selecting one of a plurality of equations, each of said plurality of equations having a different weighting for comparing said average brightness photometric values of said respective areas; calculating a scene brightness photometric value from said selected equation for each said scene; and changing an exposure control speed depending on whether a change amount of said scene has occurred, the change amount of said scene being detected based on a change in said average brightness photometric values from said step of measuring by dividing said pick-up frame or a change in said selected equation at said step of selecting one of said plurality of equations.
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10. An exposure control method for a video camera which picks up a scene with an image sensor by converting an optical image into video signals, comprising the steps of:
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periodically measuring average brightness values respectively of a plurality of areas in accordance with said video signals corresponding to each of said areas by dividing a pick-up frame of said image sensor into said plurality of areas; selecting one of a plurality of equations, each of said plurality of equations having a different weighting for comparing said average brightness values of said respective areas; determining a most frequently selected equation of said plurality of equations selected during a predetermined period; calculating a scene brightness value for each measurement from said determined equation which is used until a new determination is made after said predetermined period; and adjusting an exposure amount of said image sensor corresponding to said scene brightness value which depends upon the most frequently selected equation during said predetermined period.
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11. An exposure control method for a video camera which picks up a scene with an image sensor by converting an optical image into video signals, comprising the steps of:
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periodically measuring average brightness values respectively of a plurality of areas in accordance with said video signals corresponding to each of said areas by dividing a pick-up frame of said image sensor into said plurality of areas; calculating a scene brightness value at each measurement by selecting one of a plurality of equations, each of said plurality of equations having a different weighting for comparing said average brightness values of said respective areas; obtaining an average value of said scene brightness value selected during a predetermined period; and adjusting an exposure amount of said image sensor in response to said average value obtained during said predetermined.
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12. An exposure control method for a video camera having a pick-up frame that is divided into a plurality of areas to obtain average brightness values of each of said plurality of areas, comprising the steps of:
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comparing the average brightness values of each of said plurality of areas with each other to select one of a plurality of equations, each of said plurality of equations having a different weighting value; calculating a multi-pattern measured brightness value in accordance with the selected equation; developing a first average brightness value from a specific partial area or an overall area of said pick-up frame simultaneously with calculating said multi-pattern measured brightness value; determining whether a difference between said first average brightness value and said multi-pattern measured brightness value is greater than or equal to a predetermined threshold value; and executing an exposure control corresponding to a corrected average brightness value in response to correcting said average brightness value by an amount less than a predetermined value when said difference is greater than or equal to said predetermined threshold value.
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13. An exposure control method for a video camera comprising the steps of:
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developing a first average brightness value from substantially an overall area or a specific partial area of a pick-up frame, said pick-up frame being divided into a plurality of areas; executing an exposure control in accordance with said first average brightness value; comparing said first average brightness value for each of a plurality of areas with each other; correcting said first average brightness value by a first correction amount less than a predetermined value when the difference between said first average brightness value and said multi-pattern measured brightness value is greater than or equal to a predetermined threshold value; executing said exposure control in response to said corrected first average brightness value; developing a second correction amount for a continuous scene pickup; correcting said first correction amount corresponding to a difference between said second correction amount and said first correction amount when said difference is greater than or equal to said predetermined threshold value; and correcting said first average brightness value in response to said step of correcting said first correction amount.
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14. An exposure control method for a video camera comprising the steps of:
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developing average brightness values from a plurality of areas of a pick-up frame; comparing said average brightness values with each other; selecting one of a plurality of equations in response to said step of comparing, each of said plurality of equations having a different weighting value corresponding to said average brightness values for each of said plurality of areas; calculating a scene brightness value for an exposure control speed from said selected equation, said scene brightness value being calculated from a first weighting value for a first selected equation which gradually approaches a second weighting value from a second selected equation of a continuous scene pick-up when said second selected equation is different from said first selected equation; and determining whether a change of scene has occurred for changing said selected equation at a low speed when the change of scene has failed to occur and it is necessary to change said selected equation and changing said selected equation rapidly when the change of scene has occurred.
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15. An exposure control apparatus comprising:
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an image sensor for picking up a scene and generating a video signal; adjusting means for adjusting an exposure amount of said image sensor; detecting means for detecting a change of said scene; and stepwise changing means, responsive to said change of said scene, for stepwise changing an exposure control speed depending on whether or not the change of the scene has occurred for stably executing an exposure control.
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Specification