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) and normally appears along it as a principal color. An object-tracking control apparatus (808) tracks movement of an object (104) over the surface. As the object impacts the zone at an object-contact area (116), an impact-dependent portion (138) of the VC region temporarily appears along a print area (118) of the zone as changed color materially different from the principal color if the impact meets threshold impact criteria and if the tracking indicates that the object is highly likely to impact the object-contact area. The print area closely matches the object-contact area in size, shape, and location. Impacts of bodies not tracked by the control apparatus substantially do not cause color change so that color change occurs substantially only for suitable impacts of the tracked object.

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 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. 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. Sound-generating apparatus (602 or 702) selectively generates a specified audible sound in response to the object impacting the object-contact area so as to meet the threshold impact criteria. The specified sound is separate from any audible sound originating at the object-contact area due physically to the impact.

A variable-color region (106) of a sports-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 boundary line (1306/1308 or 1386/1388) extends along an in-bounds area (1302 or 1382) of the surface. 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 region to temporarily appear along a print area (118) of the zone as changed color materially different from the principal color. The zone typically adjoins the boundary line or an internal line (1334 or 1396).

A let detection system includes a sensor including an accelerometer attached to a tennis net. The sensor is in wireless communication with an umpire device able to send a message to the sensor, wherein the message causes the sensor to calibrate and begin monitoring for a let. The sensor determines a three-dimensional (3D) vector representing the gravity acting on the sensor as a baseline. When the sensor detects vertical acceleration of the net relative to the baseline and the vertical motion is above a preset threshold, the sensor automatically transmits a let notification message to the umpire device.

A method and system for determining whether a spherical element impacts with a component of a playing field, or arranged on or proximate thereto. The method includes acquiring images of a surveillance area of a field that covers at least part of said component, such as a delimiting perimeter line of a game area or a target, performing an approximate detection of an impact of a spherical element relative to that component or proximate thereto, with an object detection and recognition system that can discern when the detected object is indeed a spherical element, automatically selecting one of the images acquired for the same point in time and that includes the area where said impact has occurred, and analysing the selected image to check if the spherical element has impacted or not with the component.

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.