Three-dimensional measurement device

A three-dimensional measurement device, comprising:

• an irradiator that emits a predetermined light;
• an optical system that splits the predetermined light entering from the irradiator into two lights, irradiates a measurement object with one of the two lights as a measurement light and irradiates a reference plane with another of the two lights as a reference light, and combines the measurement light and the reference light with each other and emits a combined light;
• a first objective lens for the measurement light that directs the measurement light toward the measurement object;
• a second objective lens for the reference light that directs the reference light toward the reference plane;
• a first imaging device:
• comprises:
• a filter unit that comprises multiple polarizing plate sets each including four polarizing plates of 0, 45, 90, and 135 degrees, wherein
• the multiple polarizing plate sets respectively correspond to multiple split lights output from a prism that splits the combined light of a first light;
• a lens unit that comprises microlenses respectively corresponding to the polarizing plates included in the multiple polarizing plate sets;
• and
• an imaging element that comprises pixels respectively corresponding to the polarizing plates included in the multiple polarizing plate sets, and
• takes first interference fringe images of phases of 0, 45, 90, and 135 degrees;
• a second imaging device:
• comprises:
• a filter unit that comprises multiple polarizing plate sets each including four polarizing plates of 0, 45, 90, and 135 degrees, wherein
• the multiple polarizing plate sets correspond to multiple split lights output from a prism that splits the combined light of a first light;
• a lens unit that comprises microlenses respectively corresponding to the polarizing plates included in the multiple polarizing plate sets;
• and
• an imaging element that comprises pixels respectively corresponding to the polarizing plates included in the multiple polarizing plate sets, and
• takes second interference fringe images of phases of 0, 45, 90, and 135 degrees;
• one or more imaging lenses that form images of the combined light on the first and second imaging devices;
• and
• a control device that executes three-dimensional measurement of a measurement area on the measurement object based on the first and second interference fringe images, wherein
• the control device is configured to:
• obtain, by reconstruction, a plurality of pieces of intensity image data at predetermined positions with measurement range intervals within a first range along an optical axis within a specific area set in advance in the measurement area, based on the first and second interference fringe images,
• identify a first focusing position along the optical axis within the specific area, based on the pieces of intensity image data with respect to the specific area,
• obtain, by reconstruction, a plurality of pieces of intensity image data at the predetermined positions with the measurement range intervals within a second range along the optical axis set based on the first focusing position, for each coordinate in the measurement area, based on the first and second interference fringe images of the measurement area,
• identify a second focusing position along the optical axis for a predetermined coordinate in the measurement area, based on the pieces of intensity image data with respect to the predetermined coordinate,
• identify, among orders respectively corresponding to the predetermined positions along the optical axis, an order corresponding to the second focusing position along the optical axis, wherein
• the orders include zero as a reference position and positive and negative integers increasing and decreasing along the optical axis from zero,
• obtain, by reconstruction, phase information of light at the second focusing position along the optical axis for each coordinate in the measurement area, based on the first and second interference fringe images of the measurement area, and
• based on the order and the phase information, identify an actual height of a surface of the measurement object, and execute three-dimensional measurement with respect to the predetermined coordinate, and
• at least one of the first and second objective lenses have a numerical aperture NA that satisfies expressions given below:
• NA>a/√((dz)2+a2), and
• 0≤dz≤R,
• where a denotes a pixel size, dz denotes a reconstruction interval indicating an amount of shift of a reconstruction position from the focusing position along the optical axis, the reconstruction position corresponding to one of the predetermined positions that respectively correspond to the orders, and R denotes each of the measurement range intervals.