Design of a Synchronous Counter with Two-dimensional 10 x 10 LED array for Calibration of Timing Parameters of Video Cameras

Abstract

In 2011, the Standards and Calibration Laboratory (SCL) developed the video totalize method for calibration of stopwatches with the use of an in-house designed synchronous counter [1]. All digits of the LED display for the counter are updated synchronously with the clock input signal driven by a signal generator which in turn is phase locked to the caesium atomic clock, the primary frequency standard at SCL and is traceable to the Coordinated Universal Time (UTC). With a 10-digit display capable of counting long time period and a specially designed least-significant-digit (LSD) indicator to enhance the time discrimination for the measurement, this synchronous counter enables fast events to be accurately time-stamped by a high speed video camera. Detailed information on the circuit design of the SCL counter and calibration procedure of stopwatch has been discussed in the paper. The original purpose of the SCL counter is to calibrate the relative correction of a specific time interval measured by a stopwatch. With its unique features, the SCL counter can be extended to other applications, like measuring the flashing time interval of LED Lights in Toys [2], finding skipped frames in a recorded video [3], and leveraging the stroboscopic effect to calibrate the frame rate of a digital camera [4]. Through these applications, it was felt that to further improve the accuracy and extend the application areas, the function of the LSD indicator should be enhanced such as increasing the number of LEDs.