MOTION TRACKING: Cameras capture bowlers in full swing

Whether used to determine the exact position and speed of a ball or an athlete in play, vision-based systems are meeting the demands of those involved in the entertainment industry. Although machine-vision systems have been deployed in a number of broadcast applications, they are just now finding new uses in delivering added experiences for consumers involved in sports activities.

The Photo Snap system, from a leading bowling and entertainment company in India, captures key moments of play with a series of freeze-frame images. Events such as the player swinging the ball or jumping after a strike provide a memorable experience to the bowler. At the end of the bowling session, the user can then browse, e-mail, or print selected images.

The initial prototype system used a motion sensor to capture the motion of each player as they approached an individual bowling lane. A 12-V output from this sensor was then converted to 5 V using an opto-isolated voltage conversion I/O board. Once signals were converted, a USB I/O module from National Instruments (www.ni.com) individually triggered a camera to capture images of two bowling lanes and extract the half image frame for the current bowling lane. A PC-based relay control board was also used to initiate the power to both cameras and lighting during play.

To reduce the cost of the final system (see figure), a novel automation device called PowerUSB-DigitalIO from PowerUSB (www.pwrusb.com) replaced a number of these OEM components. With integrated USB I/O, 12-to-5-V conversion capability, power relay control, programmable logic control (PLC) functionality, and application programming interface (API) library, the PowerUSB-DigitalIO reduced the development time of the final system to hours and the cost to approximately $100.

An integrated digital I/O, lighting, and camera controller was used to monitor two bowling lanes, thereby reducing the cost of an automated imaging system that captures images of bowlers.

The PowerUSB-DigitalIO device integrates three software controlled power outlets—one of the outlets is used to power the camera while the other two outlets power the lighting. Under software control, the camera and lights are only powered when the bowling session is in progress. The unit also has four digital inputs. Two of these inputs are used to read the motion sensor for two lanes. When the user moves to release the ball, the motion sensor triggers the input to the PowerUSB that in turn triggers the camera to start capturing images. Because the digital inputs of PowerUSB can detect 5 to 12 V, no external 12-to-5-V converter is required.

A Canon digital SLR camera with 18-MPixel resolution was used to take continuous freeze-frame images during the bowling ball release. To reduce cost, a single camera was used to cover two-lane images with a half-frame of the image dedicated to each lane. Motion sensor data from one of the two lanes triggers the camera, which captures images and sends the half frame to the appropriate lane.

The software to control the camera and process the images was developed using C++ in VisualStudio. The server for data maintenance and image-browsing software was developed in .NET C#. Because the PowerUSB-DigitalIO provides PLC functionality, the system developer can set triggers using a simple state-matrix dialog box to control the power outlets or digital outputs.