Video camera with flicker prevention
View Patent ↗A video camera includes an image sensor. The image sensor repeatedly outputs an object scene image captured on an imaging surface. A CPU detects a luminance component of the object scene image outputted from the image sensor, i.e., an AE/AWB evaluation value, and also detects a high-frequency component of the object scene image outputted from the image sensor, i.e., an AF evaluation value. Moreover, the CPU executes a flicker determining process for determining whether or not a flicker is occurred based on the luminance component of the object scene image. However, prior to the flicker determining process, whether or not there is a dynamic object in the object scene is determined based on the high-frequency component of the object scene image. The flicker determining process is prohibited when there is the dynamic object while it is permitted when there is no dynamic object.
1. A video camera, comprising:
an imager which outputs, in a designated cycle, an electronic image representing a scene captured on an imaging surface;
an integrator which integrates, in the designated cycle, a high-frequency component of the electronic image outputted from said imager;
a first detector which detects a luminance component of the electronic image outputted from said imager;
a second detector which detects a maximum integral value and a minimum integral value from among a plurality of integral values calculated by said integrator during a time period equivalent to N (N: integer more than one) multiples of the designated cycle;
a first determiner which determines whether or not a flicker is occurred based on the luminance component detected by said first detector; and
a second determiner which determines whether or not a predetermined condition is satisfied with respect to the maximum integral value and the minimum integral value detected by said second detector so as to start said first determiner, wherein the predetermined condition is equivalent to a condition under which the maximum integral value exceeds a first threshold value and a divided value obtained by dividing the maximum integral value by the minimum integral value exceeds a second threshold value.
2. A video camera according to claim 1 , wherein said first determiner executes a determining process by noticing the luminance component detected by said first detector in parallel with a process of said integrator.
3. A video camera according to claim 1 , further comprising:
a setter which sets an exposure time period of said imager to an integral multiple of a first predetermined value; and
a changer which changes the exposure time period of said imager to a time period of an integral multiple of a second predetermined value when a determination result of said second determiner is updated from a negative result to an affirmative result.
4. A video camera according to claim 1 , wherein said second determiner stops said first determiner when the determination result indicates satisfaction of the predetermined condition.
5. A video camera according to claim 1 , wherein said imaging surface has a first number of vertical pixels and said video camera further comprises an exposure processor which exposes said imaging surface by each vertical pixels of second number which is smaller than the first number.
6. A computer program recorded on a non-transitory recording medium in order to control a video camera provided with an imager which outputs, in a designated cycle, an electronic image representing a scene captured on an imaging surface, and an integrator which integrates, in the designated cycle, a high-frequency component of the electronic image outputted from said imager, causing a processor of the video camera to execute the steps comprising:
a first detecting step of detecting a luminance component of the electronic image outputted from said imager;
a second detecting step of detecting a maximum integral value and a minimum integral value from among a plurality of integral values calculated by said integrator during a time period equivalent to N (N: integer more than one) multiples of the designated cycle;
a first determining step of determining whether or not a flicker is occurred based on the luminance component detected by said first detecting step; and
a second determining step of determining whether or not a predetermined condition is satisfied with respect to the maximum integral value and the minimum integral value detected by said second detecting step so as to start said first determining step, wherein the predetermined condition is equivalent to a condition under which the maximum integral value exceeds a first threshold value and a divided value obtained by dividing the maximum integral value by the minimum integral value exceeds a second threshold value.
7. An imaging control method executed by a video camera provided with an imager which outputs, in a designated cycle, an electronic image representing a scene captured on an imaging surface, and an integrator which integrates, in the designated cycle, a high-frequency component of the electronic image outputted from said imager, comprising:
a first detecting step of detecting a luminance component of the electronic image outputted from said imager;
a second detecting step of detecting a maximum integral value and a minimum integral value from among a plurality of integral values calculated by said integrator during a time period equivalent to N (N: integer more than one) multiples of the designated cycle;
a first determining step of determining whether or not a flicker is occurred based on the luminance component detected by said first detecting step; and
a second determining step of determining whether or not a predetermined condition is satisfied with respect to the maximum integral value and the minimum integral value detected by said second detecting step so as to start said first determining step, wherein the predetermined condition is equivalent to a condition under which the maximum integral value exceeds a first threshold value and a divided value obtained by dividing the maximum integral value by the minimum integral value exceeds a second threshold value.