Grating pattern projection apparatus using liquid crystal grating

A grating pattern projection apparatus, comprising:

• a light source;
• a liquid crystal grating;
• a projector for projecting a grating pattern formed by light emitted from the light source passing through the liquid crystal grating onto an object to be measured;
• a liquid crystal driver for driving the liquid crystal grating so that one cycle of the grating pattern has a linear intensity distribution;
• a detector for detecting a deformed grating pattern deformed by projecting the grating pattern onto an object to be measured;
• and
• a processor for converting the linear intensity distribution of each cycle of the deformed grating pattern into a linear phase distribution for changing a phase linearly,
• wherein the grating pattern includes a first grating pattern and a second grating pattern of the same grating pitch and whose intensity distributions are mutually inverse,
• the projector sequentially projects the first grating pattern and the second grating pattern individually onto an object to be measured,
• the detector sequentially detects a first deformed grating pattern caused by the first grating pattern and a second deformed grating pattern caused by the second grating pattern,
• and the processor:
• determines whether there is a fluctuation in a reflection state of an object to be measured by detecting changes in a maximum intensity and a minimum intensity of each cycle of the first deformed grating pattern and the second deformed grating pattern, and either one of positions where an intensity of the first and the second deformed grating pattern change discontinuously, or positions where the intensity sum of each position of the first and second deformed grating pattern changes discontinuously;
• and
• converts linear intensity distributions of the first and the second deformed grating pattern to linear phase distributions when the processor determines that the reflection state does not fluctuate, and
• when the processor determines that the reflection state does fluctuate, the processor:
• converts the intensity distributions within a range where the reflection state fluctuates in the linear intensity distributions of the first and the second deformed grating pattern to a first linear phase distribution for changing a phases linearly;
• converts the intensity distributions within a range where the reflection state does not fluctuate in the linear intensity distributions of the first deformed grating pattern and second deformed grating pattern to a second linear phase distribution for changing a phases linearly;
• and
• obtains a linear phase distribution by smoothly connecting the first phase distribution and the second phase distribution at positions where the intensity distributions of the first deformed grating pattern and second deformed grating pattern change discontinuously or positions where the intensity sum of the first and the second deformed grating patterns changes discontinuously.

A grating pattern projection apparatus, comprising:

• a light source;
• a liquid crystal grating;
• a projector for projecting a grating pattern formed by light emitted from the light source passing through the liquid crystal grating onto an object to be measured;
• a liquid crystal driver for driving the liquid crystal grating so that one cycle of the grating pattern has a linear intensity distribution;
• a detector for detecting a deformed grating pattern deformed by projecting the grating pattern onto an object to be measured;
• and
• a processor for converting the linear intensity distribution of each cycle of the deformed grating pattern into a linear phase distribution for changing a phase linearly,
• wherein the grating pattern includes a first grating pattern and a second grating pattern of the same grating pitch and whose intensity distributions are mutually inverse,
• the projector projects any one of the first grating pattern or the second grating pattern onto an object to be measured when the surface of an object to be measured is formed from a material of uniform reflectivity, and sequentially projects the first grating pattern and the second grating pattern onto the object to be measured when the surface of the object to be measured is formed from a material of a plurality of reflectivities, and
• the detector sequentially detects the first deformed grating pattern caused by the first grating pattern and the second deformed grating pattern caused by the second grating pattern.

A grating pattern projection apparatus, comprising:

• a light source;
• a liquid crystal grating;
• a projector for projecting a grating pattern formed by light emitted from the light source passing through the liquid crystal grating onto an object to be measured;
• a liquid crystal driver for driving the liquid crystal grating so that one cycle of the grating pattern has a linear intensity distribution;
• a detector for detecting a deformed grating pattern deformed by projecting the grating pattern onto an object to be measured;
• and
• a processor for converting the linear intensity distribution of each cycle of the deformed grating pattern into a linear phase distribution for changing a phase linearly,
• wherein the grating pattern is a pattern of one phase only,
• the projector projects a single phase grating pattern onto an object to be measured one time only,
• the detector detects a single phase deformed grating pattern caused by the single phase grating pattern one time only, and
• the processor has a single phase signal intensity fluctuation detector for detecting a peak intensity of each cycle of the single phase grating pattern, the peak intensity position, and the rate of intensity change, and a phase distribution calculator for converting the single phase deformed grating pattern to a linear phase distribution according to fluctuation of the peak intensity and rate of intensity change.

A grating pattern projection apparatus, comprising:

• a light source;
• a liquid crystal grating;
• a projector for projecting a grating pattern formed by light emitted from the light source passing through the liquid crystal grating onto an object to be measured;
• a liquid crystal driver for driving the liquid crystal grating so that one cycle of the grating pattern has a linear intensity distribution;
• a detector for detecting a deformed grating pattern deformed by projecting the grating pattern onto an object to be measured;
• and
• a processor for converting the linear intensity distribution of each cycle of the deformed grating pattern into a linear phase distribution for changing a phase linearly,
• wherein the liquid crystal driver drives the liquid crystal grating by means of a preliminary linear intensity distribution signal;
• the projector projects a preliminary grating pattern onto an object to be measured according to the preliminary linear intensity distribution signal;
• the detector detects a preliminary deformed grating pattern deformed by projecting the preliminary grating pattern onto an object to be measured, and
• the liquid crystal driver further comprises,
• an intensity distribution judgment unit for detecting a non-linear characteristic of the preliminary deformed grating pattern and positions having a non-linear characteristic, and
• a linear distribution signal corrector for, when a non-linear characteristic of the preliminary deformed grating pattern is detected, correcting the preliminary linear intensity distribution signal that the preliminary deformed grating pattern does not have a non-linear characteristic, and
• wherein the liquid crystal driver uses a corrected preliminary linear intensity distribution signal to drive the liquid crystal grating for measuring.