Disclosed is system and method for measuring the tension of a tennis net, and, alternatively or in addition, for determining if a service let occurs via the measuring of the net tension. The disclosed embodiments measure a force exerted on the center-strap or the singles stick by the net. In these embodiments, the measured force provides an accurate reflection of the tension of the net.

A variable-color region (106) of an information-presentation structure extends to an exposed surface (102) at a surface zone (112) and contains multiple variable-color cells (404), each extending to a part (406) of the zone. The cells normally appear along their parts of the zone as a principal color. Each cell that meets cellular threshold impact criteria in response to an object (104) impacting the zone at an object-contact area (116) temporarily becomes a criteria-meeting cell that temporarily appears along its part of the zone as changed color materially different from the principal color. A group of less than all the cells usually constitute criteria-meeting cells. The surface parts of the criteria-meeting cells form a print area (118) that closely matches the object-contact area in size, shape, and location. The color-change capability helps 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), 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 in size, shape, and location. The color-change component employs an electrode assembly (202) having a core layer (222) sandwiched between two electrode structures (224 and 226) for controlling the color change.

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.

Disclosed is system and method for measuring the tension of a tennis net, and, alternatively or in addition, for determining if a service let occurs via the measuring of the net tension. The disclosed embodiments measure a force exerted on the center-strap or the singles stick by the net. In these embodiments, the measured force provides an accurate reflection of the tension of the net.

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 closely matching print area (118) of the zone as changed color materially different from the principal color if the impact meets threshold impact criteria. Object-tracking apparatus (808) tracks movement of the object over the surface and provides an image-causing tracking impact signal when the object impacts the zone according to the tracking. An image-generating system (802, 842, 1152, or 1182) responds to at least the impact signal by generating a print-area vicinity image consisting of an image of the print area and adjacent area of the surface.

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. The color-change time duration of the impact-dependent portion temporarily appearing as the changed color is in a duration range established prior to the impact. A controller (602) responds to both the impact and subsequent external instruction (608) by controlling the impact-dependent portion so as to adjust the color-change duration subsequent to 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.