The dual-frequency laser interferometer is an advanced high-precision measurement instrument developed based on the single-frequency laser interferometer, utilizing heterodyne technology. It overcomes the weakness of the single-frequency laser interferometer, which is prone to environmental influences, even when the light intensity degrades.90%The dual-frequency laser interferometer can still obtain appropriate electrical signals. Due to this feature, it can calibrate block gauges, measuring rods, rulers, and coordinate measuring machines in environments with constant temperature, humidity, and vibration. It can also be used in ordinary workshops to calibrate the scales of large machine tools, enabling precise measurements over tens of meters and for minute movements like watch components. It can measure geometric quantities such as length, angle, straightness, parallelism, flatness, and perpendicularity, and is also suitable for special applications like micro-positioning in semiconductor photolithography and measuring slot spacing on computer memory chips.

The fundamental weakness of the single-frequency interferometer lies in its weak ability to handle interference. Air turbulence, oil mist from machine tools, and chip interference can all cause changes in the interference signal, thereby affecting measurement accuracy. This flaw becomes particularly pronounced in harsh testing environments and when measuring long distances. The reason for this is that it is an DC testing system, which inherently possesses the drawbacks of DC light and level zero drift. These irregular changes are difficult to compensate through the system's automatic adjustment, thus limiting the application of single-frequency laser interferometers in high-precision measurement fields.

The dual-frequency laser interferometer is an AC testing system that maintains its frequency unchanged when the intensity of the laser beam varies due to environmental factors. It does not alter its frequency due to intensity changes or level fluctuations, ensuring that interference signal frequency remains stable. Consequently, the dual-frequency interferometer boasts strong interference resistance, high precision, and reliable measurement results, finding extensive applications in high-precision semiconductor lithography machines, metrological testing, and cutting-edge scientific research.2017The human detection of gravitational waves from a binary neutron star merger was achieved using a dual-frequency laser interferometer.