The application of a Fizeau interferometer for quality check of angular scales, optical limbs, raster etc. fabricated by means of precision laser writer system CLWS-300IAE is discussed. Computer simulation and experimental results are presented. One of the promising fabrication technology of high-precision optical angular scales (OAS) for rotary encoder is direct laser writing with circular scanning, implemented on CLWS-300. Operational control of manufacturing precision is necessary for the successful implementation of this method. Currently, testing OAS with accuracy of 0.1 arcsec can be achieved only in the metrological centers. Obviously, it restrains practical application of this method. In this paper, we propose to use a standard Fizeau interferometer for operational control of OAS quality. An important feature of CLWS-300 is the ability to fabricate OAS and arbitrary diffraction structures in a single process. In this case, the linear diffraction grating (DG) and OAS have the same fabrication errors. Linear DGs wavefront distortion can be interferometrically tested in reflection under Littrow angle (Fig.1a). At the presence of writing errors, distortions of the interference pattern can be observed (Fig. 1b). Analyzing these distortions along a ring with radius R gives the values of wavefront distortion directly lead to the angular error. The angular error ε of the CLWS-300 can be calculate by ΔW～mεR/Tλ, where ΔW is the wavefront error, m is diffraction order, T is the spacing of the DG and λ is wavelength. For the parameters m=5, ε=1 arc. sec., R=20 mm, 7=2 μm we observed distortions ΔW ～ 0.025 λ (Fig.1c).
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