The present invention overcomes deficiencies of existing line-calling devices by leveraging a single fixed-location camera to identify object state conditions that resolve object-tracking problems that otherwise require multi-camera or moving-camera solutions. Though described in the context of an automated tennis line-calling device, the invention is equally applicable to other object-tracking problems that can be resolved by identifying object state conditions without employing moving or multiple cameras. The tennis line-calling device is attached to (or at least located in proximity to) the net post of a tennis court, thereby enabling a close-up view of both static (court lines) and moving (ball, players, etc.) objects. In one embodiment, integration of a video camera system with line-calling functionality provides additional benefits, including attachment of a single turnkey device to any tennis net post so as to provide automated line-calling functionality without the need for any external video cameras or processing functionality.

A collision detection system configured to determine when a ball or other object impacts against a playing surface, record the location of the object's impact, and compare the object's impact location against one or more preset virtual target areas to determine whether or not the object was successfully hit into a desired area of the playing surface and immediately reward the player with various types of audible and/or visual responses for hitting the target.

A variable-color region (106) of an information-presentation structure extends to an exposed surface (102) at a surface zone (112), normally appears along it as a principal color, and includes impact-sensitive color-change structure (132) and duration-extension structure (242). A segment (142) of the impact-sensitive color-change structure responds to an object (104) impacting the zone at an object-contact area (116) by causing an impact-dependent portion (138) of the variable-color region to temporarily appear along a print area (118) of the zone as changed color materially different from the principal color if the impact meets threshold impact criteria. The print area closely matches the object-contact area in size, shape, and location. The duration-extension structure responds to the impact by causing the impact-sensitive color-change structure to deform along an internal deformation area (288). This causes the time duration of the impact-dependent portion appearing as the changed color to be controllably extended.

A variable-color region (106) of an information-presentation structure extends to an exposed surface (102) at a surface zone (112), normally appears along it as a principal color, and includes impact-sensitive and color-change components 182 and (184). A segment (192) of the impact-sensitive component responds to an object (104) impacting the zone at an object-contact area (116) by providing an impact effect if the impact meets threshold impact criteria. A segment (194) of the color-change component responds to the impact effect by causing an impact-dependent portion (138) of the variable-color region to temporarily appear along a print area (118) of the zone as changed color materially different from the principal color. The print area closely matches the object-contact area in size, shape, and location. The color-change capability helps, for instance, in making in/out calls in sports such as tennis.

A variable-color region (106) of an information-presentation structure extends to an exposed surface (102) at a surface zone (112) and normally appears along it as a principal color. An impact-dependent portion (138) of the variable-color region responds to an object (104) impacting the zone at an object-contact area (116) by temporarily appearing along a print area (118) of the zone as changed color materially different from the principal color if the impact meets threshold impact criteria. The print area closely matches the object-contact area in size, shape, and location. An image-generating controller (806) responds to the impact by causing an image-generating structure (804) to generate an image of the print area and adjacent surface extending to at least a selected location of the exposed surface if the threshold impact criteria are met. The image assists in determining how close the impact occurred to the selected surface location.

A variable-color region (106) of an information-presentation structure extends to an exposed surface (102) at a surface zone (112) and normally appears along it as a principal color. An impact-dependent portion (138) of the variable-color region responds to an object (104) impacting the zone at an object-contact area (116) by temporarily appearing along a print area (118) of the zone as generic changed color materially different from the principal color. The print area closely matches the object-contact area in size, shape, and location. The threshold impact criteria consist of multiple sets of different threshold impact criteria respectively associated with multiple specific changed colors materially different from the principal color. If the impact meets the threshold impact criteria, the generic changed color is the specific changed color for the criteria set met by the impact.

A variable-color region (106) of an information-presentation structure extends to an exposed surface (102) at a surface zone (112) and normally appears along it as a principal color. The region responds to an object (104) impacting the zone at an object-contact area (116) by providing an impact signal if the impact meets threshold impact criteria. The impact signal identifies a threshold criteria-meeting area (1626 or 1626) where the criteria are met in the zone. Responsive to the impact signal, a controller (1622 or 1632) provides an initiation signal that designates a print area (118) in the zone such that the print area is larger than the criteria-meeting area and can closely match the object-contact area in size, shape, and location. An impact-dependent portion (138) of the region responds to the initiation signal by temporarily appearing along the print area as changed color materially different from the principal color.

A variable-color region (106) of an information-presentation structure extends to an exposed surface (102) at a surface zone (112), normally appears along it as a principal color, and includes impact-sensitive and color-change components (182 and (184). A segment (192) of the impact-sensitive component responds to an object (104) impacting the zone at an object-contact area (116) by providing an impact effect if the impact meets threshold impact criteria. A segment (194) of the color-change component responds to the effect by causing an impact-dependent portion (138) of the variable-color region to temporarily appear along a print area (118) of the zone as changed color materially different from the principal color. The print area closely matches the object-contact area. The object subsequently leaves the object-contact area. The impact-dependent portion first appears as the changed color no more than 0.2 s after the object leaves the object-contact area.

A variable-color region (106) of a football-playing or baseball/softball-playing structure of an information-presentation structure extends to an exposed surface (102) at a surface zone (112) and normally appears along it as a principal color. An impact-dependent portion (138) of the variable-color region responds to an object (104) impacting the zone at an object-contact area (116) by temporarily appearing along a closely matching print area (118) of the zone as changed color materially different from the principal color. For football, the zone typically adjoins an end or side line (1446 or 1448) to help determine whether the object, typically a person's shoe, impacted the surface in or out. For baseball/softball, the zone typically adjoins a foul line (1506) to help determine whether the object, a baseball/softball, impacted the surface fair or foul.

A variable-color region (106) of a tennis-playing structure of an information-presentation structure extends to an exposed surface (102) at a surface zone (112), normally appears along it as a principal color, and includes impact-sensitive and color-change components (182 and 184). A segment (192) of the impact-sensitive component responds to an object (104), typically a tennis ball, impacting the zone at an object-contact area (116) by providing an impact effect if the impact meets threshold impact criteria. A segment (194) of the color-change component responds to the impact effect by causing an impact-dependent portion (138) of the variable-color region to temporarily appear along a closely matching print area (118) of the zone as changed color materially different from the principal color. The zone adjoins a serviceline (34), the centerline (36), a sideline (30), or a baseline (28) to help determine whether a tennis ball impacted the surface in or out.