Virtual sport system for acquiring good image of ball by controlling camera according to surrounding brightness

A virtual sport system, comprising:

• a photographing unit comprising a camera to acquire images of a ball;
• and
• a simulator to calculate physical quantities of the ball on the basis of the images of the ball,
• wherein the photographing unit further comprises a control unit to extract visual information from at least one image acquired by the camera and determine a control signal for adjusting an exposure time or video gain of the camera on the basis of the visual information,
• wherein the control unit extracts visual information from at least one other image acquired by the camera with the adjusted exposure time or video gain, and further adjusts the exposure time or video gain of the camera if the visual information fails to meet a predefined criteria, and
• wherein the camera further acquires at least one image of a reference subject comprising at least two regions each having a uniform reflectance, the reflectances of the at least two regions being different from each other, and the control unit determines the control signal on the basis of visual information extracted from the at least one image of the reference subject with two or more regions, each region having a reflectance different from each other, such that at least some of the at least two regions in the reference subject are distinguished from a ground surface.