Patent attributes
The invention provides an electro-optical distance meter, which comprises a light emitting element for emitting a distance measuring light, signal generators for generating two or more proximity frequencies, intermittent pulse generators for generating a modulation signal in which the two or more proximity frequencies are intermitted respectively and converted to pulses with a predetermined width, a projecting optical system for sequentially switching over and projecting intermittent modulated distance measuring light as converted to pulses with predetermined width by the modulation signal, a photodetection unit for receiving a reflected distance measuring light from an object to be measured and producing an intermittent photodetection signal with a predetermined pulse width, other signal generators for generating frequency signals having a difference of a predetermined frequency with respect to the proximity frequency respectively, a frequency converting unit for performing frequency conversion by mixing the intermittent photodetection signals from the photodetection unit to a difference frequency and the frequency signals and for obtaining a signal column of intermittent conversion signals having a predetermined pulse width corresponding to each difference frequency respectively and changing by corresponding to each difference frequency respectively, and an arithmetic control unit, wherein the arithmetic control unit is configured so as to intermit the proximity frequencies so that the pulse width of the intermittent modulated distance measuring light will be shorter than a period of the difference frequency, to calculate difference frequency waveforms with respect to each of the intermittent conversion signals respectively, to calculate a precise measurement distance value by obtaining a phase from a waveform of at least one cycle of the difference frequency, to calculate a coarse measurement distance value by obtaining a phase difference between the relative difference frequencies and to determine a distance by combining the coarse measurement distance value and the precise measurement distance value.
