Method and apparatus for phase evaluation of pattern images used in optical measurement

Claim 1

An apparatus for phase evaluation of a pattern image used for optical measurement, the intensities of the pattern image being represented by a signal that is phase modulated on a carrier wave, said apparatus comprising: an array of individual detectors arranged for producing respective individual signals corresponding to the intensities of said pattern image along a minimum of five different phase steps corresponding to five different nominal phase angles of said carrier wave; first and second sets of amplifier circuits for respectively amplifying each individual intensity signal received from said detectors; a first adder circuit for receiving and accumulating the amplified individual intensity signals from said first set of amplifier circuits; a second adder circuit for receiving and accumulating the amplified individual intensity signals from said second set of amplifier circuits; said first and second sets of amplifier circuits being adapted to apply respective amplification factors to said intensity signals as a function of said five nominal phase angles of said carrier wave so that a phase error, which is the amplitude of error that results when phase steps deviate from said nominal phase steps, as a function of said phase steps, has at least three zero positions; and, an evaluation unit connected to said first and second adder circuits for determining the phase value from said phase angles.

Claim 2

An apparatus for phase evaluation of a pattern image used for optical measurement, the intensities of the pattern image being represented by a signal that is phase modulated on a carrier wave, said apparatus comprising: an array of individual detectors arranged for producing respective individual signals corresponding to the intensities of said pattern image along a minimum of five different phase steps corresponding to five different nominal phase angles of said carrier wave; first and second sets of amplifier circuits for respectively amplifying each individual intensity signal received from said detectors; a first adder circuit for receiving and accumulating the amplified individual intensity signals from said first set of amplifier circuits; a second adder circuit for receiving and accumulating the amplified individual intensity signals from said second set of amplifier circuits; said first and second sets of amplifier circuits being adapted to apply respective amplification factors to said intensity signals as a function of said five nominal phase angles of said carrier wave so that a phase error, which is the amplitude of error that results when phase steps deviate from said nominal phase steps, as a function of said phase steps, has at least three zero positions; and, an evaluation unit connected to said first and second adder circuits for determining the phase value from said phase angles.

Claim 9

An apparatus for optical measurement comprising: means for directing light to an object to be measured; means for generating a pattern image from said light directed to said object and distorted by said object, the pattern image having light intensities representing a phase modulated carrier wave being a superposition of a carrier wave and a modulation wave, the modulation resulting from distortion by said object; an array of individual detectors arranged for producing respective individual electrical output signals corresponding to the intensities of said pattern image along a minimum of five different phase angles of the carrier wave, the differences between said phase angles defining nominal phase steps; first and second convolution circuits receiving said electrical output signals of said array of individual detectors for convolving the output signals by convolution values and for assigning values to expressions Z and N and forming electrical signal outputs indicative of said expressions Z and N which represent, respectively, sine and cosine functions of said phase angles of said phase modulated wave, whereby the convolution values are selected so that a phase error, which is the amplitude of error that results when phase steps deviate from said nominal phase steps, as a function of said phase steps, has at least three zero positions; and, an arctan circuit receiving the electrical signal outputs of said convolution circuits for computing said phase value of the phase modulated wave by using the ratio Z/N.

Claim 10

An apparatus for optical measurement comprising: means for directing light to an object to be measured; means for generating a pattern image from said light directed to said object and distorted by said object, the pattern image having light intensities representing a phase modulated carrier wave being a superposition of a carrier wave and a modulation wave, the modulation resulting from distortion by said object; an array of individual detectors arranged for producing respective individual electrical output signals corresponding to the intensities of said pattern image along a minimum of five different phase angles of the carrier wave, the differences between said phase angles defining nominal phase steps; first and second convolution circuits receiving said electrical output signals of said array of individual detectors for convolving the output signals by convolution values and for assigning values to expressions Z and N and forming electrical signal outputs indicative of said expressions Z and N which represent, respectively, sine and cosine functions of said phase angles of said phase modulated wave, whereby the convolution values are selected so that a phase error, which is the amplitude of error that results when phase steps deviate from said nominal phase steps, as a function of said phase steps, has at least three zero positions; and, an arctan circuit receiving the electrical signal outputs of said convolution circuits for computing said phase value of the phase modulated wave by using the ratio Z/N.