Vehicle detection apparatus, vehicle detection program and light control apparatus

1. A vehicle detection apparatus that detects vehicles during hours of darkness, the apparatus comprising:

an image acquisition unit that repeatedly acquires an image of a road;

a light source detection unit that detects one or more light sources which are an order of magnitude more than a predetermined brightness from each acquired image;

a variation detecting unit that repeatedly detects a brightness of each light and an area occupied by, each of the one or more detected light sources within the total area of each acquired image, and determines that a given detected light source is a variable brightness light source if the brightness of that light source is changed within a reference time beyond a predetermined brightness variation reference value and determines that a given detected light source is a variable area light source if the area occupied by that light source is changed within a reference time beyond a predetermined area variation reference value; and

a determining unit that counts the number of times a given detected light source is determined to be a variable brightness light source and the number of times the given detected light source is determined to be a variable area light source, and determines whether a vehicle exists in the acquired image based on the number of times that the given detected light source is determined to be the variable brightness light source and the number of times that the given detected light source is determined to be the variable area light source; wherein,

the determining unit determines that the vehicle exists only when the number of times for the given detected light source that the variable brightness is detected is more than a first threshold of the number of times and the number of times for the given detected light source that the variable area is detected is more than a second threshold of the number of times.

2. A vehicle detection apparatus according to claim 1 , wherein,

the variation detecting unit classifies a given detected light source as a variable brightness light source or as a variable area light source when the brightness or area respectively increases by more than a threshold within a reference time, and then the brightness or area respectively decreases thereafter.

3. A vehicle detection apparatus according to claim 1 , wherein,

the variation detecting unit calculates the brightness of each pixel that constitutes a given acquired image,

and is configured so that the brightness of a given detected light source is calculated using the brightness of each pixel when the variation detecting unit calculates the brightness of each pixel, wherein

the brightness of a specific pixel is calculated in consideration of the brightness of the specific pixel itself, and the brightness of adjacent pixels.

4. A vehicle detection apparatus according to claim 1 , wherein,

the determining unit measures, for a given detected light source, intervals between when the variation detecting unit determines variability of the brightness and intervals between when the variation detecting unit determines variability of the area, and determines that the given detected light source is not from a vehicle if the intervals between determinations are periodic.

5. A vehicle detection apparatus according to claim 1 , wherein, there is provided a program stored on a computer readable non-transient memory for configuring a computer to provide each unit of the vehicle detection apparatus.

6. A vehicle detection apparatus according to claim 1 , further comprising:

a light control apparatus controlling an optical axis of headlights in the vehicle, and

a changing unit that changes an illumination angle of at least one of the headlights downward when the oncoming vehicles are detected.