This PDF file contains the front matter associated with SPIE Proceedings Volume 9687, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and Conference Committee listing.

The Physikalisch-Technische Bundesanstalt (PTB) has developed and set up a deflectometer with sub-millimetre lateral resolution. This device uses an enhanced deflectometric method called ‘Exact Autocollimation Deflectometric Scanning’ (EADS), which makes use of two angle sensors. One angle sensor has a small beam aperture and scans the specimen by using a pentaprism or a double mirror unit. It operates as a null angle sensor and controls the tilting of the specimen by means of a piezo actuator, so that the reflected beam of the specimen always propagates back in the same direction. The null-angle sensor allows sub-millimetre apertures with sensitivities of better than 0.01 arcsec to be achieved. The tilt of the specimen is measured with the second angle sensor – usually a commercially available autocollimator – with a large aperture at a fixed distance. The surface topography is obtained by the numerical integration of the measured tilt angles. The measurement uncertainty associated with the resulting topography typically scales with the scan length. Here, we present measurements with different lateral resolutions down to 0.3 mm.

The advent of high-brilliance synchrotron radiation sources with low emittance and high degree of coherence has urged the development of super-smooth x-ray mirrors, which have sub-nanometer height errors and sub-50-nrad slope errors. To ensure the optical performance and avoid procuring significantly more expensive mirrors than necessary, knowledge of the mirror surface power spectral density (PSD) function is required over a wide spatial frequency range. In addition, a better understanding of the diffraction effects of different spatial frequencies is required to guide the specification of the mirror in the beamline design phase. In this work, two typical x-ray beam focusing conditions for the proposed APS upgrade are studied: the diffraction limited focusing and the demagnification dominated focusing. The effects of surface errors are studied using both the method described by Church and Takacs¹ and numerical simulations with HYBRID². Using this information, we show how the mirror specification depends on the mirror PSD.

Over the past decade, the concept of x-ray Deformable Mirror (DM) has matured from early experimental stages to a standard tool now available at many synchrotron/free-electron laser facilities. Indeed, x-ray active optics has become an integral part of all present and future large x-ray and EUV projects and will be essential in exploiting the full potential of the new sources currently under construction. These DMs mainly are employed to correct wavefront errors or provide variable x-ray beam sizes. Due to the coupling between the N actuators of a DM, it is usually necessary to perform a calibration or training step to be able to control the DM to the right target. To determine the optimum actuators settings in order to minimize slope/height errors, an initial measurement need to be collected, with all actuators set to 0 and then either N or 2N measurements are necessary. In this work, we present a fast and accurate method to drive an x-ray active bimorph mirror to a target shape with only 3 or 4 measurements. Instead of sequentially measuring and calculating the influence functions of all actuators and then predicting the needed voltages for any desired shape, we make use of the metrology data to directly guide the mirror from current status towards the particular target slope/shape via iterative compensations. The feedback for the iteration process is the discrepancy in curvature determined by height/slope measurement data. Experiments demonstrate the feasibility of this simple approach.

The Wolter mirror is a promising imaging device for soft x-ray microscopy owing to its excellent characteristics. Its annular aperture enables high-NA design while maintaining high photon transfer efficiency. However, its deep and narrow cylinder-like shape makes its fabrication difficult. Despite its long history, the Wolter mirror has not been practically used for high-resolution microscopy. We have been developing a fabrication process for grazing incidence mirrors with rotationally symmetric shapes. The mirrors are replicated from precisely machined mandrels. We employ electroforming as a replication method with high replication accuracy and reproductivity. Here, we report the first fabrication of a Wolter mirror and discuss the replication quality in electroforming. The imaging quality of Wolter mirror is also evaluated in an observation experiment using a visible-light microscope.

The quality of X-ray optics on beamline is a key factor that limits the performance of the beam line to play. For X-ray mirror surface characterization with high accuracy, long trace profiler and NOM for flat or slight curved mirror have been developed. However, these two kind of instruments cannot measure the highly curved mirror since requirement of high precision and that of large range contradict each other. In this paper, we proposed a novel wavefront-coding-based surface slope metrology technique. Four-dimension information of the optics under test, including x-y position and sagittal/tangential angle, is provided. Due to the focused beam used and the high speed DMD (Digital Mirror Device), high spatial resolution of the measurement is obtained. In experiment, we demonstrated this technique by measuring bend-based high energy monochromator developed in BSRF.

The scattering from residual optical fabrication errors in the middle spatial frequency range limits the resolution and signal-to-noise ratio of optical systems. An optical profiler is a useful tool for characterization of residual surface roughness for middle spatial frequencies. An accurate calibration and measurement strategy of the optical profiler are critical for accurate optical metrology. In this manuscript, the optical profiler is calibrated using two methods. The first one is the median filter method, based on the oblique line power spectral density of a super-smooth surface. The super-smooth surface was considered as a standard and the measured data were calibrated for a normal optical surface. The use of the median filter enables us to extend the effective frequency of the measured data. The second method applies multiple measurement and is built on the primary spectral characteristics of white noise: a random signal with a constant power spectral density and an oblique line power spectral density for a fractal surface. Through multiple measurement, the white noise decreases and more accurate values for the surface height can be obtained. Both methods can extend the ranges of effective spatial frequency and optimize the capability and utilization of the optical profiler.

The flatness is one of the important geometric quantity such as a silicon wafer, a photo mask and ultra-precise optics for an extreme ultraviolet lithography, synchrotron radiation facilities and a gravitational wave interferometer. A Fizeau interferometer is in a high accurate flatness measurement equipment. In a Fizeau interferometer, the measurand is a gap distance between a reference flat and a specimen. The measurement accuracy of the Fizeau interferometer is limited by the flatness of the reference flat. The flatness of commercially reference flats is about λ/40 to λ/20 (15 nm - 30 nm). There is strong demand for developing that the flatness of reference flat is less than 10 nm. Thus, we developed a λ/100 (6.3 nm) reference flat which is attachable to a commercial Fizeau interferometer. The measurable diameter of the optical flat was φ100 mm. In the factory fields, the flatness of the reference flat mounted on a commercial Fizeau interferometer is required. We designed the reference flat using the finite element method (FEM) to decrease a deformation by mounting. The developed reference flat was evaluated by a scanning deflectometric profiler (SDP) and an ultra-high accurate Fizeau interferometer. Finally, the reference flat was validated through the evaluation results.

To meet the requirements of wavelength matching and figure preservation for EUV multilayer optics, study of precise control of the lateral thickness gradients of multilayer was performed. The distribution of the magnetron sputtering source was derived by fitting the coating thickness profiles of flat substrates sweeping across the source with constant velocity at different heights using genetic algorithm. Then, genetic algorithm was also used in finding the proper speed profiles for the desired thickness profiles. By the method mentioned above, extremely precise control of the lateral thickness gradients of multilayer on curved substrates was realized.

Light spot centroid detection is one of the key technologies in optical measurement. In order to overcome the poor stability caused by small scale spot, we proposed an extract method by using saturated light spot in this paper. By increasing the input voltage of LED and adjusting the exposure time of CCD, the image of LED which projected in the image plane become larger, it can help enhancing the stability of light spot centroid extracting. The experiment results showed that the extract stability of saturated light spot has improved obviously compared with small scale spot. This method can be adopted in close range measurement; it reflected the sub-pixel coordinate of spot in image plane coordinate more accurately after calibrating the distorted image.

X-ray Nano-Computed Tomography (Nano-CT) is widely used in micro device nondestructive testing, material science, life science and other applications fields. Micro-focus X-ray source is one of the key components of Nano-CT and is directly affected by the quality of electron beam. Diameter is the key performance index of electron beam. The detection of electron beam spot diameter is of great significance for monitoring the performance of Nano-CT and quantitatively evaluating the qualities of design and fabrication of the electron gun and electron optical system. In this paper, the diameter direct detecting method is presented and applied to the FEI Quanta 600 SEM. The relationship between electron beam diameter and detecting curve is analyzed at first, then the application feature of diameter detecting methods, including crosshair detecting method, slit detecting method and single edge detecting method, is researched and compared. Furthermore, the experimental results demonstrate that the edge detection has higher detecting accuracy and lower requirement on the sampler, and that after computation the detecting error is within 20 nm.

In order to promote the measurement accuracy to sub-50 nrad rms for both spherical and plane mirror tests and to resolve the difficulty in testing strongly curved mirror by use of the NOM, the Nano-accuracy Surface Profiler (NSP) was developed. The NSP system applies scanning sampling beam in fixed scanning distance combined with non-tilted reference beam for removing pitch error of scanning slide to ensure sub-50 nrad rms accuracy measurement. The NSP takes the advantage of the NOM in using precise autocollimator (Elcomat 3000) for both sampling and reference beams. In preliminary test, this NSP scheme verifies it has at least the same measurement accuracy as the NOM for plane mirror test. The NSP system scheme significantly reduces test error than the NOM for sphere test, and it also ensures the capability using single calibration curve to further correct systematic error in reaching sub-50 nrad rms accuracy for spherical mirror test.

Recently, metrology in the fields of synchrotron- and X-ray optics entered the nano-accuracy and sub-50 nrad rms range. In addition to developing novel surface profilers, now dedicated specific measurement technologies play very important roles in reducing errors in measurements. All facts, producing an error of about 10 nrad rms, must be treated very carefully. A temperature stability of 0.01-0.02°C (P-V) over 24 hours is one of most important parameters in ensuring nano-accuracy. The Elcomat 3000/8 autocollimator has large saw-tooth error of 269 nrad rms, which must be suppressed. A fixed reading location setting method shuns the saw-tooth impact, so that it is possible to reach sub-50 nrad rms accuracy in measuring a precise plane mirror. A dense measurement method, combined with finding a peakvalley center to remove saw-tooth effectively promotes accuracy for sphere test. In this paper, we detail a graphic method of combining multiple FW/BW scans in selecting stable files that can reduce the error by10-15 nrad rms.The alignment of precise parallelism between the autocollimator’s axis and the direction of the slide’s movement are introduced, and some nano-accuracy tests are introduced.

A long trace profiler in NSRRC is used to develop a bendable mirror, for the mirror-mounting mechanism and to inspect the mirrors of TPS beamlines. We upgraded the air bearing, the motor and gear, the penta-mirror, the CCD and the software. ELCOMATT 3000 is our calibration reference. To maintain constant the measurement of the optical path, we adopted a scheme for a moving optical head that decreases the various optical paths through a focusing lens to avoid lens homogeneity. The measurement environment (temperature, vibration, air turbulence) is effectively controlled. In measuring a curved mirror (radius 9.7 m), the repeatability is below 0.1 μrad. This paper describes the upgraded performance and engineering details.

The push for high quality x-ray optics is closely linked to improvements in metrology technology. During the last decade, we have seen an ultra-fast progress in x-ray optics performances. This enhancement is directly linked to the development of the necessary tools to control these optical components. These metrology tools are necessary for the fabrication (to guide some polishing deterministic process) and also for the ultimate characterization used to validate surface parameters (often inside their own mechanical support) prior to installation in a beam line. It is now necessary to characterize optical surface figure, slope errors and roughness on meter-long optics over spatial frequencies as short as 0.1 mm and with slope errors reaching less than 100 nrad rms or surface figure errors close to 1 nm in order to not spoiled and preserve the high brightness made available by third and fourth generation synchrotron/FEL sources like NSLSII or LCLS. For this purpose, the new NSLS-II Optical Metrology Laboratory (NSLSII-OML) includes commercial instruments for measuring long spatial frequency figure errors, mid spatial frequencies and high frequency roughness and had started some research and development activities. This paper provides a brief description of the instruments currently available in the laboratory and gives an overview of the very active research and development efforts within the NSLSII-OML.