Portable apparatus and method for testing and certification of laser-based speed measuring devices

A self-contained, multi-function test and measurement apparatus used to test and measure the performance of a laser gun, comprising:

• internal control means for selecting and directing at least one of a plurality of selected test and measurement functions;
• and
• means, operationally coupled to said internal control means, for measuring or verifying the capability of said laser gun to accurately measure at least two of the following:
• a double pulse detection;
• pulse frequency within a prescribed range of a designed pulse frequency;
• pulse width within a prescribed range of a designed pulse width;
• optical power within a prescribed maximum limit;
• actual wavelength within a prescribed range of a designed wavelength;
• speed simulation;
• internal clock frequency;
• and sight alignment to determine that said sight alignment is within a prescribed range of a value required for proper operation of said laser gun.

A method for certifying the operation of a laser-gun-type speed measurement device, comprising:

• performing a ‘pulse width’ test of the laser, including the steps of:
• a) applying a first operating voltage to the laser gun;
• b) directing an output of the laser gun into an optical detector;
• c) obtaining an output of the optical detector in the form of low-level current pulses;
• d) converting the low-level current pulses into a corresponding voltage;
• e) comparing the corresponding voltage to a reference voltage and determining whether an ‘in-range’ condition is present and, if yes;
• f) converting the low-level current pulses into high-level voltage pulses, wherein the high-level voltage pulses directly represent a pulse train output of the laser gun;
• g) providing a sampling circuit including eight parallel sampling paths that operate at phase differences which are successively 45 degrees apart, wherein each cycle of eight samples contains a series of ‘1 ’ or ‘0 ’ bits in an 8-bit data block that represent whether a pulse from the laser gun was present ('1′) or not present (‘0’) at the time the sample was taken;
• h) accumulating 512 8-bit data blocks in a memory;
• i) counting the ‘1 ’ bits in all 512 data blocks;
• j) using a known sample time to calculate an effective pulse width of the laser gun output;
• k) determining whether the calculated effective pulse width is within a specified range of a laser gun reference pulse width and, if no,
• l) concluding the test;
• otherwise,
• m) determining whether the ‘pulse width’ test is to be repeated at a different operating voltage and, if yes,
• n) applying at least a second operating voltage to the laser gun;
• and
• o) repeating steps (b-o) until the test has been performed at all selected operating voltages.