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Purpose: Schools have a significant role in ensuring children's wellbeing as children spend a lot of time at school. Students need to have an active role in their learning and an opportunity to participate in issues concerning wellbeing and studying. This research examines students' wellbeing in an innovative learning environment. The classroom is built with professionals, teachers and students (aged 9). The authors call it Learning Ground. Design/methodology/approach: Students' wellbeing was measured with smart device application for a six-week period. Students answered the questionnaire with a Likert scale of five (very poor - excellent) responses. Two weeks during the six weeks research period, students were able to use digital study aids, EEG-biosensor headsets, to observe the effectiveness of their learning, defined by NeurSky app. The EEG-biosensors enabled students to use a tool to recognise their own learning factors during the lessons. The effectiveness was available to students via tablets all the time. Findings: The students at the Learning Ground are satisfied with wellbeing and the environment support for students' wellbeing experience is notable. They have "good vibes" before and after the school day. When wearing EEG-headsets "study aids", which enabled them to observe their learning via tablets at lessons, the wellbeing experience in the mornings even increased. Originality/value: Schools need to be visionaries concerning 21st century learning and children's wellbeing. Building flexible learning environments and bringing innovative technologies into schools to provide active support for students will enable 21st century learning. Wellbeing of children should become first when developing the future schools.

We present a method of numerical analysis of interferograms for a diffractive-lens-based common-path interferometer recently introduced by Elfstrom et al. [Opt. Express 14, 3847 (2006)]. Practical aspects such as the effect of higher diffraction orders upon the interferograms are considered. We show that this method can be used to solve the phase function of the inspected lens. In addition, we show that by using this method it is possible to estimate the focal length and imaging properties of the inspected lens. OCIS codes: 120.3180, 050.1965.

Radial diffractive gratings are used to couple light of a white LED into a light guide. Theoretical coupling efficiencies are evaluated with rigorous diffraction theory in a pure conical mounting. It is shown that when the refractive index of the grating increases from 1.46 to 2.05 the incoupling efficiency increases from 42% to 63%. Also, with the increasing refractive index the incoupling efficiency is shown to become more nearly uniform over the visible spectrum. Experimental results for the incoupled efficiencies and the color coordinates of the incoupled spectra are introduced for refractive indices n = 1.46 and n = 1.56. OCIS codes: 230.0230, 230.1950, 230.7400, 050.1970.

Ring-shaped and radial diffractive gratings are designed with rigorous diffraction theory to couple light of a nearly monochromatic LED into a thin planar light guide on the bottom side. The theoretical coupling efficiencies for ring-shaped and radial gratings are 41% and 66%, respectively. Optimized diffractive elements are manufactured with direct electron-beam lithography and reactive-ion-etching into Si[O.sub.2] substrates. Good agreement between experimental and theoretical results for selected radial gratings is reached. Furthermore, the mass production tests using injection molding are carried out with good replicability. OCIS codes: 050.1970, 230.1950, 230.7400.

We address the problem of shaping the radiant intensity distribution of a highly nonparaxial coherent field by means of a diffractive element located in the plane of the beam waist. To be capable of wide-angle energy redistribution the element must necessarily contain wavelength-scale transverse features, and consequently it must be designed on the basis of rigorous diffraction theory. We consider, in particular, wide-angle Gaussian to flat-top beam shaping in one dimension. Scalar designs are provided and their validity is evaluated by rigorous diffraction theory, which is also used for optimization deep inside the nonparaxial domain, where the scalar designs fail. Experimental verification is provided by means of electron-beam lithography.