Subdivision and direction recognition of λ/16 of orthogonal fringes for nanometric measurement

Abstract

Subdivision is one of the essential methods to improve the measurement resolution of optical instruments. A new method is proposed to solve lambda/16 bidirectional subdivision and direction recognition for orthogonal interference signals by constructing two sets of reference signals and using zero-cross detection. The experimental results prove that the method is efficient for orthogonal signals and has good real-time performance by field-programmable gate array realization. This method is easy to realize by use of electronic design automation tools and can be widely used in the signal processing system of optical measurement instruments such as a moiré fringe measurement system and laser interferometer.

Optical Interference Signal Processing in Precision Dimension Measurement

“…3.4 λ/2 n+2 bidirectional subdivision (Hu et al, 2009) and (Hu & Zhang, 2012) proposes a method of λ/2 n+2 bidirectional subdivision that uses both the constructed function and the cross-zero detection. The λ/8 and λ/16 bidirectional subdivision methods are simply introduced at first.…”

“…(Cheng et al, 2009) uses the normalized waveforms to eliminate DC offsets and amplitude variation. (Hu & Zhang, 2011) proposes a method for detection and elimination of the nonorthogonal errors based on digital sampled signals as follows when (Hu et al, 2009, Hu & Zhang, 2012 are applied in the fringe subdivision.…”

“…If the nonorthogonality error does not exist, Eq. 43 can be represented by the λ/8 bidirectional subdivision from (Hu et al, 2009) as follows:…”

“…With the development of electronic and computer technologies, many platforms are widely used in the signal processing for orthogonal signals, such as the hardware (Birch, 1990, Downs & Birch, 1983, FPGA (Hu et al, 2009), the software programming (Zhang et al, 1994, Su et al, 2000, LabVIEW (Yacoot et al, 2001), DSP (Zumberge et al, 2004), and so on. Besides the analog signal processing and the digital signal processing, the image processing is also an important method to realize the fringe analysis (Takeda et al, 1982, Qian, 2004.…”

A Novel Quadrature Signal Estimation Method for a Planar Capacitive Incremental Displacement Sensor

“…A look-up table was used offline to compensate for interpolation errors [11]. Hu et al proposed a method to solve λ/16 bidirectional subdivision for quadrature signals by constructing two sets of reference signals [12]. However, these methods would easily neglect displacement information in a single period.…”