High-dynamic-range laser range finders based on a novel multimodulated frequency method

A continuous-wave phase-shift laser range finder employs a novel multimodulation frequency method associating an undersampling analog-digital converter (ADC) with digital synchronous detection. This presentation greatly improves measured phase accuracy and reduces prior art scheme complexities. The novel patented design includes one phase-lock-loop (PLL) chip to produce a multimodulation frequency, one analog-to-digital converter operating at a low sampling rate, and an effective algorithm to calculate the final distance, which has encoded computing codes, and is implemented into compact computing circuits but without mixers and redundant components. The experimental results prove that a nonambiguity range is easily achieved to 1.5 Km when the modulation frequency is operated at 0.1 MHz. The measured accuracy approaches 2.9 mm using the same apparatus when the modulation frequency is tuned to 14.5 MHz. Dynamic range can reach 5.2 × 10⁵ without a very high modulation frequency below 15 MHz, as revealed by a detailed analysis.