ZYGO 4104C

Description

Model Series

Technical Specifications

Functional Features

• Full-aperture surface figure measurement in a single acquisition
• Flatness testing with PV and RMS output
• Sphericity and asphericity measurement using Zernike polynomial decomposition
• Radius of curvature (ROC) determination for both concave and convex surfaces
• Optical power measurement (PV, RMS, best-fit sphere, best-fit parabola)
• Step height measurement for coated or uncoated optical components
• Thin-film thickness measurement using fringe-counting algorithms
• Automated alignment via computer-controlled tip/tilt and translation stages
• Pass/Fail analysis with user-defined tolerances
• 3D surface map generation with color-coded deviation plots
• Zernike polynomial analysis up to 36th order (standard), expandable to 72nd order
• Time-series / vibration analysis capability
• Multi-wavelength mode for resolving ambiguity in step-height measurements
• Data export in multiple formats: PDF, CSV, ZMX, DAT, BMP, TXT

Performance Parameters

Material Composition

Structural Features

• Fizeau interferometer optical configuration: laser beam splits at a beamsplitter, one path reflects off the internal reference surface, the other off the test surface; recombined beams create interference fringes
• Transmission-type reference flat/sphere: light passes through the reference surface twice, doubling sensitivity and eliminating back-reflection errors
• Computer-controlled 5-axis alignment stage: X, Y, Z translation plus tip and tilt for automated positioning
• Integrated CCD camera: mounted at the output port of the interferometer, captures full-aperture fringe pattern in a single frame
• Z-axis piezoelectric scanner: provides sub-nanometer vertical displacement for phase-shifting interferometry (PSI)
• Enclosed optical path: sealed housing minimizes air turbulence and dust contamination
• Air refractive index compensation sensor: built-in temperature, pressure, and humidity sensors feed real-time corrections into the measurement algorithm
• Touchscreen or PC-based control interface: MetroPro software runs on a dedicated Windows workstation
• Modular aperture turret: allows switching between aperture sizes without realignment (on select configurations)

Working Principle

1. A frequency-stabilized HeNe laser at 632.8 nm emits a coherent beam
2. The beam enters a beamsplitter cube and divides into two paths:
   • Reference path: reflects off the internal high-precision reference surface (flat or sphere)
   • Test path: reflects off the surface under test (SUT)
3. The two beams recombine at the beamsplitter and form an interference fringe pattern
4. The CCD camera captures the fringe pattern across the full aperture
5. Phase-shifting interferometry (PSI): the Z-axis piezo scanner moves the reference surface in precise steps (typically 4 or 5 steps), capturing multiple frames to extract the phase map
6. The MetroPro software processes the phase data to reconstruct a 3D surface map of the SUT
7. The software calculates PV, RMS, Zernike coefficients, power, radius of curvature, and other parameters relative to a user-selected reference (best-fit sphere, best-fit plane, etc.)
8. Air refractive index corrections are applied in real time using measured environmental conditions

Advantages and Highlights

• Sub-nanometer vertical resolution (0.1 nm) with full-aperture coverage
• λ/200 RMS surface figure accuracy — industry-leading for production metrology
• λ/1000 RMS repeatability ensures measurement consistency across repeated tests
• Full-aperture acquisition in seconds — dramatically faster than point-by-point profilometers
• Automated alignment eliminates operator skill dependency
• Zernike polynomial decomposition enables direct comparison to optical design specifications
• Pass/Fail with tolerance overlay supports production-line quality control
• Non-contact measurement — zero force applied to the optic under test
• Environmentally compensated — internal sensors correct for air index variations
• MetroPro software provides complete analysis, archiving, and reporting in one package
• Modular aperture system supports multiple optic sizes on a single instrument
• Long-term stability — frequency-stabilized laser eliminates wavelength drift

Applicable Industries

Installation Requirements

Usage Precautions

• Never look directly into the laser beam — 632.8 nm HeNe laser is Class 2/3R; direct eye exposure causes retinal damage
• Do not touch optical surfaces (reference or test) with bare fingers — use lint-free gloves or handles
• Allow 30-minute warm-up time before precision measurements for laser frequency stabilization
• Keep the interferometer enclosure closed during measurement to prevent air currents from distorting fringes
• Do not exceed the specified aperture size for the installed reference surface — using a larger optic than the aperture causes vignetting and measurement error
• Clean optics only with approved solvents (methanol or isopropanol) and lint-free wipes; never use acetone on coated surfaces
• Avoid thermal shock — do not place hot or cold optics directly onto the stage; allow thermal equilibration
• Do not operate in environments with excessive vibration (>0.5 μm amplitude) — this degrades fringe contrast and measurement accuracy
• Perform regular reference surface calibration using certified reference flats/spheres at intervals defined by the quality system
• Store the system in a clean, dry, temperature-controlled environment when not in use
• Do not disassemble the sealed optical head — internal alignment is factory-set and requires certified service
• Update MetroPro software to the latest version for improved algorithms and bug fixes
• Log all environmental conditions (temperature, pressure, humidity) at time of measurement for traceability

Software Package

Key Parameters Summary (Bold Reference)