Non-contacting caliper measurements of free standing sheets such as porous polymer and paper detect mid-IR interferometric fringes created by the reflection of light from the top and bottom surfaces of the sheet. The technique includes directing a laser beam at a selected angle of incidence onto a single spot on the exposed outer surface wherein the laser beam comprises radiation having a wavelength in the 3-50 micron range and scanning the laser beam through a selected angle range as the laser beam is directed onto the exposed outer surface and measuring the intensity of an interference pattern that forms from the superposition of radiation that is reflected From the exposed outer surface and from the inner surface. Thickness can be extracted from the fringe separation in the interference pattern. Rotating and focusing elements ensure that the spot position on the sheet remains the same while varying the incident angle.

An embodiment provides a light reflection support and a through hole inspection system including the same, wherein the light reflection support stably fixes and supports a glass substrate, an inspection target, and reflects illumination light to a lower part of a glass substrate arranged on the opposite side of an imaging part to increase inspection precision from a clear imaged image of a through hole. The light reflection support is used in a device that images a through hole formed in a substrate and inspects whether the through hole is normal from the imaged image, and includes a transparent support part and a reflection layer part. The transparent support part supports the substrate and has a suction hole that extends to a solid area of the substrate where the through hole is not formed.

An apparatus for measuring a step difference between a lip and a shim of a slot die includes: a laser sensor configured to measure a step difference between a lip and a shim of a slot die, the laser sensor being disposed to face the lip and the shim of the slot die, and a jig configured to come into contact with at least a part of the body where a portion of the slot die from which the ink is discharged is positioned. A method to implementing the same.

A measurement apparatus for measuring a thickness of a semiconductor wafer includes: an optical system configured to perpendicularly irradiate a sample wafer and a reference wafer with light, and receive interference signals of the light reflected on front and back surfaces of the respective wafers; a signal processor configured to perform frequency analysis of the interference signals received by the optical system to obtain peak positions of a point spread function of the respective wafers; and a calculator configured to calculate a thickness tsample of the sample wafer based on the peak position x of the sample wafer and the peak position y of the reference wafer obtained by the signal processor, and a thickness treference of the reference wafer.