Tag: Dual-Frequency Laser Interferometer

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 Dual-Frequency Laser Interferometer: Principles, Usage, Maintenance, Repair, and Brands Overvie

I. Principles of Dual-Frequency Laser Interferometer

The dual-frequency laser interferometer, an advanced measurement instrument based on heterodyne interference principles, evolves from the single-frequency laser interferometer. It utilizes two laser beams of different frequencies for interference measurement, achieving high-precision measurement of various physical quantities such as displacement, length, and angle. This instrument finds wide application in precision machining, metrological inspection, and scientific research, serving as a crucial tool for enhancing equipment accuracy and detection efficiency.

Working Principles:

  • Based on the Zeeman splitting effect and frequency pulling effect.
  • A magnetic field of approximately 0.03 Tesla is applied to a He-Ne laser, generating left- and right-handed circularly polarized light with two different frequencies (f1 and f2).
  • After processing through a series of optical elements, these beams are split into reference and measurement beams.
  • When the movable mirror shifts, the frequency of the measurement beam changes (f2 ± Δf) due to the Doppler effect, while the reference beam’s frequency remains constant.
  • The two beams interfere on a photodetector, producing an electrical signal containing the frequency difference Δf. By counting the changes in frequency difference, the displacement of the movable mirror can be calculated.

Key Components:

  • Laser Source: Employs a laser, such as a He-Ne laser or semiconductor laser, to generate two laser beams with different frequencies.
  • Optical Beam Splitting: The laser beam is divided into two beams by a beam splitter, one serving as the reference beam and the other as the measurement beam.
  • Optical Path Design: The reference beam follows a fixed path, while the measurement beam traverses a variable path. The two beams recombine in the interferometer, producing interference fringes.
  • Interference Fringes: The movement of interference fringes reflects changes in the length of the measurement path. Precise calculations of the displacement or length changes of the measured object can be derived by analyzing these fringes.
  • Signal Processing: The interference fringe signal is converted into an electrical signal by a photodetector and processed to obtain measurement results.

II. Usage Instructions

  1. System Connection: Connect the laptop, laser interferometer, environmental compensation unit, printer, etc., via communication cables and power them on.
  2. Laser Warm-up: Turn on the laser interferometer and allow it to warm up for about 15-20 minutes. Proceed with measurements once the laser is stable (indicator light turns green).
  3. Software Initialization: Start the measurement software on the laptop and enter the corresponding measurement subroutine.
  4. Optical Mirror Installation: Secure the laser interferometer, reflectors, beam splitters, and other optical components on the measurement tripod and machine tool in appropriate positions, and adjust for alignment.
  5. Target Value Setting: Set target values according to measurement requirements and program the CNC measurement procedure.
  6. Data Collection: Initiate the data collection program for automatic or manual data acquisition and monitor the measurement data.

III. Common Faults and Repair Methods

  1. Laser Fault:
    • Symptom: Laser does not emit light or has insufficient intensity.
    • Repair: Check the laser power supply and connection cables, ensuring proper power supply. Replace the laser if necessary.
  2. Optical Path Deviation:
    • Symptom: Interference fringes are unclear or disappear.
    • Repair: Adjust the positions of the beam splitter and reflector to ensure parallel optical paths and accurate beam convergence points.
  3. Photodetector Fault:
    • Symptom: Signal is unstable or there is no signal output.
    • Repair: Check the detector’s power supply and connection cables, clean the detector surface to ensure normal operation.
  4. Environmental Interference:
    • Symptom: Measurement results are highly variable or inaccurate.
    • Repair: Isolate the instrument from environmental vibrations and temperature changes, ensuring a stable working environment.
  5. Signal Processor Fault:
    • Symptom: Data collection is unstable or analysis results are erroneous.
    • Repair: Check signal processor connections and software settings, reinstall or update software if necessary.

IV. Precautions and Maintenance

  • Environmental Requirements: Place the instrument in a dry, clean, and vibration-free environment, avoiding the impact of moisture and dust on optical components.
  • Handling and Storage: Hold the base when moving the instrument to prevent guide rail deformation; store optical components in a clean and dry container when not in use.
  • Cleaning and Lubrication: Avoid wiping mirrors and beam splitters unless necessary, using scientific methods for cleaning; regularly lubricate moving parts to maintain good working condition.
  • Usage Norms: Avoid forced rotation, hard pulling, and other improper operations; apply appropriate force to each adjustment component.

V. Brands and Models of Dual-Frequency Laser Interferometers Repaired by Longi Electromechanical Company

  1. Renishaw
    • XL-80: High-precision laser interferometer system
    • HS20: Dual-frequency laser interferometer for large-range position measurement
  2. Keysight Technologies (formerly Agilent Technologies)
    • 5519A/B: Dual-frequency laser interferometer for high-precision positioning and measurement
    • 5530: Laser interferometer system supporting various measurement applications
  3. Zygo Corporation
    • ZMI 4000 Series: Dual-frequency laser interferometer for high-precision position and speed measurement (ZMI 4500, ZMI 4100)
    • ZMI 2000 Series: High-performance dual-frequency laser interferometer (ZMI 2400, ZMI 2002)
  4. SIOS Messtechnik
    • SP 2000 Series: Dual-frequency laser interferometer system for precise length and angle measurement (SP 2000, SP 2000 TR)
    • SP 5000 Series: High-resolution dual-frequency laser interferometer (SP 5000 NG, SP 5000 TR)
  5. Hamar Laser Instruments
    • L-730 Series: Dual-frequency laser interferometer for machine calibration and alignment (L-730, L-740)
    • L-750 Series: High-precision dual-frequency laser interferometer (L-750)
  6. API (Automated Precision Inc.)
    • XD Series: High-precision laser interferometer system (XD6, XD8)
  7. Renishaw/Anorad (Collaborative Brand)
    • RLE Series: High-performance laser interferometer (RLE10, RLE20)
  8. Mahr Metrology
    • MarForm MFU Series: High-precision laser interferometer for shape measurement and surface contour measurement (MFU 100, MFU 200)
  9. Mitutoyo
    • Laser 20: Dual-frequency laser interferometer for high-precision position measurement
    • Laser 30: High-performance dual-frequency laser interferometer
  10. Status Pro
    • EZ-EL Series: High-precision laser interferometer system (EZ-EL-A, EZ-EL-B)
  11. Tokyo Seimitsu
    • LV-50
  12. Marposs
    • BLU Series:
      • BLU LT: For length and displacement measurement
      • BLU LI: For straightness and angle measurement

Longi Electromechanical Company specializes in the repair of dual-frequency laser interferometers, with nearly 30 years of experience. We can quickly repair various instruments and also offer the recycling and sale of used dual-frequency laser interferometers. Welcome to consult us.