1. Field of the Invention
The present invention relates to a laser range detector and more particularly pertains to a method and apparatus for a laser range detector to detect a distance precisely.
2. Description of the Related Art
It is convenient to use a laser beam to detect the distance from a laser range detector to a target point.
FIG. 1 of the drawings illustrates a structure of a laser range detector in the prior art. A MPU 130 outputs a trigger signal to a clock unit 120, the clock unit 120 receives the trigger signal and outputs an emitting signal to an emitter 110 and outputs a clock signal to a sampler 160. The emitter 110 receives the emitting signal and outputs a pulse S0 to a target point and a receiver 150 receives a pulse S1 reflected from the target point, the features of the pulse S1, for example, the waveform or the period are similar to the pulse S0. The receiver 150 outputs the pulse S1 to the sampler 160. The sampler 160 samples the pulse S1 according to the clock signal and outputs pulse clock data corresponding to the pulse S1 to a register 170. The register 170 stores the pulse clock data. The MPU 130 receives the pulse clock data from the register 170 and calculates the time between the pulse S0 and S1, then calculates the distance to a target point.
A problem with the laser range detector is the precision of the detection. As illustrated in FIG. 2, a pulse S0 is output by a laser range detector, a pulse S1 and a pulse S2 are reflected by the target and are received by a laser range detector, wherein the pulse S1 and S2 are sampled at the same clock so the distances calculated are the same (both at 122th clock). In fact, the distances are different because the pulse S11 and S21 are not the same. A faster clock generator can improve the precision of the detection because a pulse can be sampled more times. But a faster clock generator is expensive and a circuit working at a faster clock is complicated.
In view of the foregoing disadvantage inherent in the laser range detector in the prior art, it is one object of the present invention to provide a method and an apparatus to detect a distance precisely for a laser range detector.
To attain the object, the present invention provides a method for a laser range detector to detect a distance precisely. The method including the following steps: first, emitting a first signal to a target; second, receiving a second signal which is the first signal reflected by the target; then generating one or more delay signals; then generating a plurality of pulse clock data from sampling the second signal or the delay signals; then calculating a precise time according to the pulse clock data; and calculating a precise distance according to the precise time, wherein each delay signal is delayed for a multiple default time from the second signal and the period of the second signal is smaller than the default time.
To attain the object,.the present invention provides an apparatus for a laser range detector to generate a plurality of delay signals, the apparatus including: an input terminal for inputting a second signal; and one or more delay units for generating one or more delay signals; and a switching circuit for selectively outputting one of the second signals or the delay signals; wherein the feature of the delay signal is similar to the second signal.
To attain the object, the present invention provides an apparatus for a laser range detector to detect a distance precisely, the apparatus including: a processor for calculating a precise time and a precise distance; and a clock generator for outputting clock signals; and an emitter for emitting a first signal to a target; and a receiver for receiving a second signal collided from a target; and a delay circuit for passing the second signal and outputting one or more delay signals; and a sampler for sampling the second signal or the delay signals; and-a register for storing a plurality of pulse clock data corresponding to the second signal or the delay signals; wherein the feature of the second signal and the delay signals are similar to the first signal.