Recently the demand of the metrology for large asphere and freeform optics are increasing for digital camera and other area. We have developed new technology having the accuracy is less 0.1 um and scanning speed is 30 mm/s using the linear motor and the air bearing system based on the He-Ne stabilized frequency laser coordinate measurement system. By using this technology, we developed form measurement machine UA3P-650H, having larger measurement area XY 500 mm and Z 120 mm for asphere and freeform surfaces.
When we think about asphere and freeform measurement, the form accuracy is needed not only the deviation from bestfit radius form but also the absolute radius form, by reason of the focal length is depending on the absolute dimension of surface form. In this case, it’s suitable to use He-Ne frequency stabilized laser which has the traceability to the international length standard.
And we will introduce how to measure freeform surfaces and the off axis asphere by using this technology.
For the increasing demand for the measurement of mobile and smart phone aspherical lenses, we have developed automatic measurement function additionally conventional UA3P series. And we have developed special unit and function for this machine to measure 4,000 lenses on the single wafer.

Coordinate Measuring Machines (CMMs) are considered as the most accurate metrology equipment and are used widely in the manufacturing sector. Traditionally, touch trigger probes have been employed but more recently non-contact laser scanning sensors have been developed, offering potential advantages in terms of speed and number of points captured. Laser scanning is attracting significant interest from industry due to its ability to characterise complex, free-form surface geometries which are becoming common in the styling of automotive body panels. However, laser scanning sensors do not currently offer the accuracy and repeatability that can be achieved with touch trigger probes. Furthermore, there are no recognised standards for qualifying non-contact probes, making reliable verification of measurements difficult to achieve. Past research has attempted to qualify the capability of different non-contact probing technologies using small artefacts designed for technology validation; however, little work has been done on the verification of on-CMM laser scanning technologies for large volume, industry-relevant measurement applications. This study used a full-scale machined physical representation of a sheet metal vehicle body to evaluate the measurement agreement and repeatability of a laser scanning sensor, relative to touch trigger probe measurements, mounted on a horizontal arm CMM using individual surface points, edge points and circular holes, located across the entire structure. Through the use of a static repeatability analysis it was found that there was good correlation between touch trigger probe and laser scanner measurements. Repeatability of the laser scanner was found to be better than 28 µm for surface, edge and circular holes measurement. Accuracy of the laser scanner relative to the touch trigger probe measurements fell within a range of 50 µm which is a factor of 10 lower than typical automotive body-shell manufacturing tolerances. The results collected demonstrate that laser scanning sensor and CMM used in this study would provide a level of accuracy and repeatability better than which is typically required by automotive manufacturers for body-in-white quality inspection applications.

Spherical concaves with high numerical apertures are required in industry for lithography optics in ultraviolet (UV) and X-ray wavelengths. Systematic error in the interferometric test of these surfaces are aberrations due to imperfect alignment, gravitational effect, geometrical effect of nonuniform phase shift, aberrations of converging optics, phase-shift nonlinearity, mechanical vibration, and so on. Gravitational deformation of a 4-inch spherical concave surface was measured in a vertical Fizeau interferometer. Aberrations caused by the deformation was separated and extracted from the total deviations of a sphericity measurement in an absolute test of two spherical comparisons. After subtracting the gravitation deformation from the shape of the spherical concave, we can define a neutral surface which is free from gravity. The gravitational sag in a horizontally placed spherical surface could be measured if we measure the difference of surface shape deviation from this neutral shape. Dominant alignment errors, coma and spherical aberrations were estimated numerically. Experimental results show that the aberrations caused by gravity amount to 7 nm peak-to-valley (PV).

Recently, the resolution of length measurements based on optical interferometry reached sub-nanometer order. However, the accuracy of the optical interferometry is limited by the knowledge of absolute air refractive index. In this work, we have proposed a method to measure the absolute air refractive index by measuring the free-spectral-range and the resonance frequency of a Fabry-Perot cavity, whose inside is filled by vacuum and by air. During the air refractive index measurement, the geometrical length of the Fabry-Perot cavity must be constant in vacuum and in air. In this paper, a compensation of the Fabry-Perot cavity length deformation owing to a large pressure difference between air and vacuum is proposed.

Big challenges in precision measurement technology nowadays lead to the creation and improvement of a big variety of optical and tactile probes. This development concerns a nanosensor system on the basis of a non-contact laser focus probe (base sensor) which presents high resolution and low uncertainty. Optical and mechanical probing methods are combined on the basis of a laser focus sensor, thus allowing the combination of various interactions between sensor and specimen. For these purposes, the deflection of the probing sensor (cantilever or stylus) is measured directly without contact using the laser beam of the focus sensor. The significant advantage of the developed nanosensor system results from its modularity and versatility. Scanning laser focus sensors are a viable alternative enabling the measurement of non-periodic features. Severe limitations are imposed by the diffraction limit determining the edge location accuracy. A rigorous model for the simulation of the diffraction of three-dimensional focussed optical beams from line space patterns has been developed and applied to improve the edge detection accuracy of a laser focus sensor. The validation of this method is realised by means of an AFM part of the nanosensor system.
Moreover, the possibility of using the laser focus senor not only for precision measurements, but also for the direct generation of precision nanostructures by means of lithography can be shown. Here, compared with classical lithography the goal is to ensure the capability of processing freeform structures on tilted surfaces.