A structure comprising a digital displacement sensor and a measured object wherein the digital displacement sensor comprises: a signal acquisition module, wherein the signal acquisition module includes at least two photoelectric sensors, the two photoelectric sensors are configured to acquire a first signal and a second signal respectively and send the first signal and the second signal to a signal processing unit, the first signal includes wave peaks and wave valleys, the wave peaks and the wave valleys are periodically distributed, the digital displacement sensor is configured to detect a length of the measured object, the measured object is provided with a measurement coating, the measurement coating includes two stripes with different reflection efficiencies, widths of the two stripes are the same, and the photoelectric sensors obtain signals by sensing the measurement coating in a detection whereby a waveform of the second signal is the same as a waveform of the first signal, and in a same clock period, the wave peaks of the first signal correspond to wave valleys of the second signal, and a phase difference between the first signal and the second signal is 180 degrees; and the signal processing unit is configured for generating a third signal, wherein in the same clock period, a descending waveform of a third signal is generated at a first intersection point of the waveforms of the first signal and the second signal and an ascending waveform of the third signal is generated at a second intersection point of the waveforms of the first signal and the second signal, forming a waveform of the third signal in one clock period; and a data processing unit configured for counting the ascending waveforms and the descending waveforms of the third signal to digitize a length measurement result, the distance of the photoelectric sensor is defined as follows: d=h+x·2·h, where d is the distance between the center points of the two photoelectric sensors, h is the width of a single stripe, x is a natural number and its physical meaning is the number of cycles, and the distance (a) of the spacing between the signal acquisition module and measured object varies from 0.1 mm to 5 mm. a signal acquisition module, wherein the signal acquisition module includes at least two photoelectric sensors, the two photoelectric sensors are configured to acquire a first signal and a second signal respectively and send the first signal and the second signal to a signal processing unit, the first signal includes wave peaks and wave valleys, the wave peaks and the wave valleys are periodically distributed, the digital displacement sensor is configured to detect a length of the measured object, the measured object is provided with a measurement coating, the measurement coating includes two stripes with different reflection efficiencies, widths of the two stripes are the same, and the photoelectric sensors obtain signals by sensing the measurement coating in a detection whereby a waveform of the second signal is the same as a waveform of the first signal, and in a same clock period, the wave peaks of the first signal correspond to wave valleys of the second signal, and a phase difference between the first signal and the second signal is 180 degrees; and the signal processing unit is configured for generating a third signal, wherein in the same clock period, a descending waveform of a third signal is generated at a first intersection point of the waveforms of the first signal and the second signal and an ascending waveform of the third signal is generated at a second intersection point of the waveforms of the first signal and the second signal, forming a waveform of the third signal in one clock period; and a data processing unit configured for counting the ascending waveforms and the descending waveforms of the third signal to digitize a length measurement result, the distance of the photoelectric sensor is defined as follows: d=h+x·2·h, where d is the distance between the center points of the two photoelectric sensors, h is the width of a single stripe, x is a natural number and its physical meaning is the number of cycles, and the distance (a) of the spacing between the signal acquisition module and measured object varies from 0.1 mm to 5 mm.